v4.19.13 snapshot.
diff --git a/mm/filemap.c b/mm/filemap.c
new file mode 100644
index 0000000..52517f2
--- /dev/null
+++ b/mm/filemap.c
@@ -0,0 +1,3331 @@
+/*
+ * linux/mm/filemap.c
+ *
+ * Copyright (C) 1994-1999 Linus Torvalds
+ */
+
+/*
+ * This file handles the generic file mmap semantics used by
+ * most "normal" filesystems (but you don't /have/ to use this:
+ * the NFS filesystem used to do this differently, for example)
+ */
+#include <linux/export.h>
+#include <linux/compiler.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/sched/signal.h>
+#include <linux/uaccess.h>
+#include <linux/capability.h>
+#include <linux/kernel_stat.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/uio.h>
+#include <linux/hash.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+#include <linux/blkdev.h>
+#include <linux/security.h>
+#include <linux/cpuset.h>
+#include <linux/hugetlb.h>
+#include <linux/memcontrol.h>
+#include <linux/cleancache.h>
+#include <linux/shmem_fs.h>
+#include <linux/rmap.h>
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/filemap.h>
+
+/*
+ * FIXME: remove all knowledge of the buffer layer from the core VM
+ */
+#include <linux/buffer_head.h> /* for try_to_free_buffers */
+
+#include <asm/mman.h>
+
+/*
+ * Shared mappings implemented 30.11.1994. It's not fully working yet,
+ * though.
+ *
+ * Shared mappings now work. 15.8.1995 Bruno.
+ *
+ * finished 'unifying' the page and buffer cache and SMP-threaded the
+ * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
+ *
+ * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
+ */
+
+/*
+ * Lock ordering:
+ *
+ * ->i_mmap_rwsem (truncate_pagecache)
+ * ->private_lock (__free_pte->__set_page_dirty_buffers)
+ * ->swap_lock (exclusive_swap_page, others)
+ * ->i_pages lock
+ *
+ * ->i_mutex
+ * ->i_mmap_rwsem (truncate->unmap_mapping_range)
+ *
+ * ->mmap_sem
+ * ->i_mmap_rwsem
+ * ->page_table_lock or pte_lock (various, mainly in memory.c)
+ * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
+ *
+ * ->mmap_sem
+ * ->lock_page (access_process_vm)
+ *
+ * ->i_mutex (generic_perform_write)
+ * ->mmap_sem (fault_in_pages_readable->do_page_fault)
+ *
+ * bdi->wb.list_lock
+ * sb_lock (fs/fs-writeback.c)
+ * ->i_pages lock (__sync_single_inode)
+ *
+ * ->i_mmap_rwsem
+ * ->anon_vma.lock (vma_adjust)
+ *
+ * ->anon_vma.lock
+ * ->page_table_lock or pte_lock (anon_vma_prepare and various)
+ *
+ * ->page_table_lock or pte_lock
+ * ->swap_lock (try_to_unmap_one)
+ * ->private_lock (try_to_unmap_one)
+ * ->i_pages lock (try_to_unmap_one)
+ * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
+ * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
+ * ->private_lock (page_remove_rmap->set_page_dirty)
+ * ->i_pages lock (page_remove_rmap->set_page_dirty)
+ * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
+ * ->inode->i_lock (page_remove_rmap->set_page_dirty)
+ * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
+ * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
+ * ->inode->i_lock (zap_pte_range->set_page_dirty)
+ * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
+ *
+ * ->i_mmap_rwsem
+ * ->tasklist_lock (memory_failure, collect_procs_ao)
+ */
+
+static int page_cache_tree_insert(struct address_space *mapping,
+ struct page *page, void **shadowp)
+{
+ struct radix_tree_node *node;
+ void **slot;
+ int error;
+
+ error = __radix_tree_create(&mapping->i_pages, page->index, 0,
+ &node, &slot);
+ if (error)
+ return error;
+ if (*slot) {
+ void *p;
+
+ p = radix_tree_deref_slot_protected(slot,
+ &mapping->i_pages.xa_lock);
+ if (!radix_tree_exceptional_entry(p))
+ return -EEXIST;
+
+ mapping->nrexceptional--;
+ if (shadowp)
+ *shadowp = p;
+ }
+ __radix_tree_replace(&mapping->i_pages, node, slot, page,
+ workingset_lookup_update(mapping));
+ mapping->nrpages++;
+ return 0;
+}
+
+static void page_cache_tree_delete(struct address_space *mapping,
+ struct page *page, void *shadow)
+{
+ int i, nr;
+
+ /* hugetlb pages are represented by one entry in the radix tree */
+ nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(PageTail(page), page);
+ VM_BUG_ON_PAGE(nr != 1 && shadow, page);
+
+ for (i = 0; i < nr; i++) {
+ struct radix_tree_node *node;
+ void **slot;
+
+ __radix_tree_lookup(&mapping->i_pages, page->index + i,
+ &node, &slot);
+
+ VM_BUG_ON_PAGE(!node && nr != 1, page);
+
+ radix_tree_clear_tags(&mapping->i_pages, node, slot);
+ __radix_tree_replace(&mapping->i_pages, node, slot, shadow,
+ workingset_lookup_update(mapping));
+ }
+
+ page->mapping = NULL;
+ /* Leave page->index set: truncation lookup relies upon it */
+
+ if (shadow) {
+ mapping->nrexceptional += nr;
+ /*
+ * Make sure the nrexceptional update is committed before
+ * the nrpages update so that final truncate racing
+ * with reclaim does not see both counters 0 at the
+ * same time and miss a shadow entry.
+ */
+ smp_wmb();
+ }
+ mapping->nrpages -= nr;
+}
+
+static void unaccount_page_cache_page(struct address_space *mapping,
+ struct page *page)
+{
+ int nr;
+
+ /*
+ * if we're uptodate, flush out into the cleancache, otherwise
+ * invalidate any existing cleancache entries. We can't leave
+ * stale data around in the cleancache once our page is gone
+ */
+ if (PageUptodate(page) && PageMappedToDisk(page))
+ cleancache_put_page(page);
+ else
+ cleancache_invalidate_page(mapping, page);
+
+ VM_BUG_ON_PAGE(PageTail(page), page);
+ VM_BUG_ON_PAGE(page_mapped(page), page);
+ if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
+ int mapcount;
+
+ pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
+ current->comm, page_to_pfn(page));
+ dump_page(page, "still mapped when deleted");
+ dump_stack();
+ add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+
+ mapcount = page_mapcount(page);
+ if (mapping_exiting(mapping) &&
+ page_count(page) >= mapcount + 2) {
+ /*
+ * All vmas have already been torn down, so it's
+ * a good bet that actually the page is unmapped,
+ * and we'd prefer not to leak it: if we're wrong,
+ * some other bad page check should catch it later.
+ */
+ page_mapcount_reset(page);
+ page_ref_sub(page, mapcount);
+ }
+ }
+
+ /* hugetlb pages do not participate in page cache accounting. */
+ if (PageHuge(page))
+ return;
+
+ nr = hpage_nr_pages(page);
+
+ __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+ if (PageSwapBacked(page)) {
+ __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
+ if (PageTransHuge(page))
+ __dec_node_page_state(page, NR_SHMEM_THPS);
+ } else {
+ VM_BUG_ON_PAGE(PageTransHuge(page), page);
+ }
+
+ /*
+ * At this point page must be either written or cleaned by
+ * truncate. Dirty page here signals a bug and loss of
+ * unwritten data.
+ *
+ * This fixes dirty accounting after removing the page entirely
+ * but leaves PageDirty set: it has no effect for truncated
+ * page and anyway will be cleared before returning page into
+ * buddy allocator.
+ */
+ if (WARN_ON_ONCE(PageDirty(page)))
+ account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
+}
+
+/*
+ * Delete a page from the page cache and free it. Caller has to make
+ * sure the page is locked and that nobody else uses it - or that usage
+ * is safe. The caller must hold the i_pages lock.
+ */
+void __delete_from_page_cache(struct page *page, void *shadow)
+{
+ struct address_space *mapping = page->mapping;
+
+ trace_mm_filemap_delete_from_page_cache(page);
+
+ unaccount_page_cache_page(mapping, page);
+ page_cache_tree_delete(mapping, page, shadow);
+}
+
+static void page_cache_free_page(struct address_space *mapping,
+ struct page *page)
+{
+ void (*freepage)(struct page *);
+
+ freepage = mapping->a_ops->freepage;
+ if (freepage)
+ freepage(page);
+
+ if (PageTransHuge(page) && !PageHuge(page)) {
+ page_ref_sub(page, HPAGE_PMD_NR);
+ VM_BUG_ON_PAGE(page_count(page) <= 0, page);
+ } else {
+ put_page(page);
+ }
+}
+
+/**
+ * delete_from_page_cache - delete page from page cache
+ * @page: the page which the kernel is trying to remove from page cache
+ *
+ * This must be called only on pages that have been verified to be in the page
+ * cache and locked. It will never put the page into the free list, the caller
+ * has a reference on the page.
+ */
+void delete_from_page_cache(struct page *page)
+{
+ struct address_space *mapping = page_mapping(page);
+ unsigned long flags;
+
+ BUG_ON(!PageLocked(page));
+ xa_lock_irqsave(&mapping->i_pages, flags);
+ __delete_from_page_cache(page, NULL);
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+
+ page_cache_free_page(mapping, page);
+}
+EXPORT_SYMBOL(delete_from_page_cache);
+
+/*
+ * page_cache_tree_delete_batch - delete several pages from page cache
+ * @mapping: the mapping to which pages belong
+ * @pvec: pagevec with pages to delete
+ *
+ * The function walks over mapping->i_pages and removes pages passed in @pvec
+ * from the mapping. The function expects @pvec to be sorted by page index.
+ * It tolerates holes in @pvec (mapping entries at those indices are not
+ * modified). The function expects only THP head pages to be present in the
+ * @pvec and takes care to delete all corresponding tail pages from the
+ * mapping as well.
+ *
+ * The function expects the i_pages lock to be held.
+ */
+static void
+page_cache_tree_delete_batch(struct address_space *mapping,
+ struct pagevec *pvec)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ int total_pages = 0;
+ int i = 0, tail_pages = 0;
+ struct page *page;
+ pgoff_t start;
+
+ start = pvec->pages[0]->index;
+ radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
+ if (i >= pagevec_count(pvec) && !tail_pages)
+ break;
+ page = radix_tree_deref_slot_protected(slot,
+ &mapping->i_pages.xa_lock);
+ if (radix_tree_exceptional_entry(page))
+ continue;
+ if (!tail_pages) {
+ /*
+ * Some page got inserted in our range? Skip it. We
+ * have our pages locked so they are protected from
+ * being removed.
+ */
+ if (page != pvec->pages[i])
+ continue;
+ WARN_ON_ONCE(!PageLocked(page));
+ if (PageTransHuge(page) && !PageHuge(page))
+ tail_pages = HPAGE_PMD_NR - 1;
+ page->mapping = NULL;
+ /*
+ * Leave page->index set: truncation lookup relies
+ * upon it
+ */
+ i++;
+ } else {
+ tail_pages--;
+ }
+ radix_tree_clear_tags(&mapping->i_pages, iter.node, slot);
+ __radix_tree_replace(&mapping->i_pages, iter.node, slot, NULL,
+ workingset_lookup_update(mapping));
+ total_pages++;
+ }
+ mapping->nrpages -= total_pages;
+}
+
+void delete_from_page_cache_batch(struct address_space *mapping,
+ struct pagevec *pvec)
+{
+ int i;
+ unsigned long flags;
+
+ if (!pagevec_count(pvec))
+ return;
+
+ xa_lock_irqsave(&mapping->i_pages, flags);
+ for (i = 0; i < pagevec_count(pvec); i++) {
+ trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
+
+ unaccount_page_cache_page(mapping, pvec->pages[i]);
+ }
+ page_cache_tree_delete_batch(mapping, pvec);
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+
+ for (i = 0; i < pagevec_count(pvec); i++)
+ page_cache_free_page(mapping, pvec->pages[i]);
+}
+
+int filemap_check_errors(struct address_space *mapping)
+{
+ int ret = 0;
+ /* Check for outstanding write errors */
+ if (test_bit(AS_ENOSPC, &mapping->flags) &&
+ test_and_clear_bit(AS_ENOSPC, &mapping->flags))
+ ret = -ENOSPC;
+ if (test_bit(AS_EIO, &mapping->flags) &&
+ test_and_clear_bit(AS_EIO, &mapping->flags))
+ ret = -EIO;
+ return ret;
+}
+EXPORT_SYMBOL(filemap_check_errors);
+
+static int filemap_check_and_keep_errors(struct address_space *mapping)
+{
+ /* Check for outstanding write errors */
+ if (test_bit(AS_EIO, &mapping->flags))
+ return -EIO;
+ if (test_bit(AS_ENOSPC, &mapping->flags))
+ return -ENOSPC;
+ return 0;
+}
+
+/**
+ * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
+ * @mapping: address space structure to write
+ * @start: offset in bytes where the range starts
+ * @end: offset in bytes where the range ends (inclusive)
+ * @sync_mode: enable synchronous operation
+ *
+ * Start writeback against all of a mapping's dirty pages that lie
+ * within the byte offsets <start, end> inclusive.
+ *
+ * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
+ * opposed to a regular memory cleansing writeback. The difference between
+ * these two operations is that if a dirty page/buffer is encountered, it must
+ * be waited upon, and not just skipped over.
+ */
+int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
+ loff_t end, int sync_mode)
+{
+ int ret;
+ struct writeback_control wbc = {
+ .sync_mode = sync_mode,
+ .nr_to_write = LONG_MAX,
+ .range_start = start,
+ .range_end = end,
+ };
+
+ if (!mapping_cap_writeback_dirty(mapping))
+ return 0;
+
+ wbc_attach_fdatawrite_inode(&wbc, mapping->host);
+ ret = do_writepages(mapping, &wbc);
+ wbc_detach_inode(&wbc);
+ return ret;
+}
+
+static inline int __filemap_fdatawrite(struct address_space *mapping,
+ int sync_mode)
+{
+ return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
+}
+
+int filemap_fdatawrite(struct address_space *mapping)
+{
+ return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
+}
+EXPORT_SYMBOL(filemap_fdatawrite);
+
+int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
+ loff_t end)
+{
+ return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
+}
+EXPORT_SYMBOL(filemap_fdatawrite_range);
+
+/**
+ * filemap_flush - mostly a non-blocking flush
+ * @mapping: target address_space
+ *
+ * This is a mostly non-blocking flush. Not suitable for data-integrity
+ * purposes - I/O may not be started against all dirty pages.
+ */
+int filemap_flush(struct address_space *mapping)
+{
+ return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
+}
+EXPORT_SYMBOL(filemap_flush);
+
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping: address space within which to check
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+bool filemap_range_has_page(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ pgoff_t index = start_byte >> PAGE_SHIFT;
+ pgoff_t end = end_byte >> PAGE_SHIFT;
+ struct page *page;
+
+ if (end_byte < start_byte)
+ return false;
+
+ if (mapping->nrpages == 0)
+ return false;
+
+ if (!find_get_pages_range(mapping, &index, end, 1, &page))
+ return false;
+ put_page(page);
+ return true;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
+static void __filemap_fdatawait_range(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ pgoff_t index = start_byte >> PAGE_SHIFT;
+ pgoff_t end = end_byte >> PAGE_SHIFT;
+ struct pagevec pvec;
+ int nr_pages;
+
+ if (end_byte < start_byte)
+ return;
+
+ pagevec_init(&pvec);
+ while (index <= end) {
+ unsigned i;
+
+ nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
+ end, PAGECACHE_TAG_WRITEBACK);
+ if (!nr_pages)
+ break;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pvec.pages[i];
+
+ wait_on_page_writeback(page);
+ ClearPageError(page);
+ }
+ pagevec_release(&pvec);
+ cond_resched();
+ }
+}
+
+/**
+ * filemap_fdatawait_range - wait for writeback to complete
+ * @mapping: address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the given address space
+ * in the given range and wait for all of them. Check error status of
+ * the address space and return it.
+ *
+ * Since the error status of the address space is cleared by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ */
+int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
+ loff_t end_byte)
+{
+ __filemap_fdatawait_range(mapping, start_byte, end_byte);
+ return filemap_check_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_range);
+
+/**
+ * file_fdatawait_range - wait for writeback to complete
+ * @file: file pointing to address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the address space that file
+ * refers to, in the given range and wait for all of them. Check error
+ * status of the address space vs. the file->f_wb_err cursor and return it.
+ *
+ * Since the error status of the file is advanced by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ */
+int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ __filemap_fdatawait_range(mapping, start_byte, end_byte);
+ return file_check_and_advance_wb_err(file);
+}
+EXPORT_SYMBOL(file_fdatawait_range);
+
+/**
+ * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
+ * @mapping: address space structure to wait for
+ *
+ * Walk the list of under-writeback pages of the given address space
+ * and wait for all of them. Unlike filemap_fdatawait(), this function
+ * does not clear error status of the address space.
+ *
+ * Use this function if callers don't handle errors themselves. Expected
+ * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
+ * fsfreeze(8)
+ */
+int filemap_fdatawait_keep_errors(struct address_space *mapping)
+{
+ __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
+ return filemap_check_and_keep_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
+
+static bool mapping_needs_writeback(struct address_space *mapping)
+{
+ return (!dax_mapping(mapping) && mapping->nrpages) ||
+ (dax_mapping(mapping) && mapping->nrexceptional);
+}
+
+int filemap_write_and_wait(struct address_space *mapping)
+{
+ int err = 0;
+
+ if (mapping_needs_writeback(mapping)) {
+ err = filemap_fdatawrite(mapping);
+ /*
+ * Even if the above returned error, the pages may be
+ * written partially (e.g. -ENOSPC), so we wait for it.
+ * But the -EIO is special case, it may indicate the worst
+ * thing (e.g. bug) happened, so we avoid waiting for it.
+ */
+ if (err != -EIO) {
+ int err2 = filemap_fdatawait(mapping);
+ if (!err)
+ err = err2;
+ } else {
+ /* Clear any previously stored errors */
+ filemap_check_errors(mapping);
+ }
+ } else {
+ err = filemap_check_errors(mapping);
+ }
+ return err;
+}
+EXPORT_SYMBOL(filemap_write_and_wait);
+
+/**
+ * filemap_write_and_wait_range - write out & wait on a file range
+ * @mapping: the address_space for the pages
+ * @lstart: offset in bytes where the range starts
+ * @lend: offset in bytes where the range ends (inclusive)
+ *
+ * Write out and wait upon file offsets lstart->lend, inclusive.
+ *
+ * Note that @lend is inclusive (describes the last byte to be written) so
+ * that this function can be used to write to the very end-of-file (end = -1).
+ */
+int filemap_write_and_wait_range(struct address_space *mapping,
+ loff_t lstart, loff_t lend)
+{
+ int err = 0;
+
+ if (mapping_needs_writeback(mapping)) {
+ err = __filemap_fdatawrite_range(mapping, lstart, lend,
+ WB_SYNC_ALL);
+ /* See comment of filemap_write_and_wait() */
+ if (err != -EIO) {
+ int err2 = filemap_fdatawait_range(mapping,
+ lstart, lend);
+ if (!err)
+ err = err2;
+ } else {
+ /* Clear any previously stored errors */
+ filemap_check_errors(mapping);
+ }
+ } else {
+ err = filemap_check_errors(mapping);
+ }
+ return err;
+}
+EXPORT_SYMBOL(filemap_write_and_wait_range);
+
+void __filemap_set_wb_err(struct address_space *mapping, int err)
+{
+ errseq_t eseq = errseq_set(&mapping->wb_err, err);
+
+ trace_filemap_set_wb_err(mapping, eseq);
+}
+EXPORT_SYMBOL(__filemap_set_wb_err);
+
+/**
+ * file_check_and_advance_wb_err - report wb error (if any) that was previously
+ * and advance wb_err to current one
+ * @file: struct file on which the error is being reported
+ *
+ * When userland calls fsync (or something like nfsd does the equivalent), we
+ * want to report any writeback errors that occurred since the last fsync (or
+ * since the file was opened if there haven't been any).
+ *
+ * Grab the wb_err from the mapping. If it matches what we have in the file,
+ * then just quickly return 0. The file is all caught up.
+ *
+ * If it doesn't match, then take the mapping value, set the "seen" flag in
+ * it and try to swap it into place. If it works, or another task beat us
+ * to it with the new value, then update the f_wb_err and return the error
+ * portion. The error at this point must be reported via proper channels
+ * (a'la fsync, or NFS COMMIT operation, etc.).
+ *
+ * While we handle mapping->wb_err with atomic operations, the f_wb_err
+ * value is protected by the f_lock since we must ensure that it reflects
+ * the latest value swapped in for this file descriptor.
+ */
+int file_check_and_advance_wb_err(struct file *file)
+{
+ int err = 0;
+ errseq_t old = READ_ONCE(file->f_wb_err);
+ struct address_space *mapping = file->f_mapping;
+
+ /* Locklessly handle the common case where nothing has changed */
+ if (errseq_check(&mapping->wb_err, old)) {
+ /* Something changed, must use slow path */
+ spin_lock(&file->f_lock);
+ old = file->f_wb_err;
+ err = errseq_check_and_advance(&mapping->wb_err,
+ &file->f_wb_err);
+ trace_file_check_and_advance_wb_err(file, old);
+ spin_unlock(&file->f_lock);
+ }
+
+ /*
+ * We're mostly using this function as a drop in replacement for
+ * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
+ * that the legacy code would have had on these flags.
+ */
+ clear_bit(AS_EIO, &mapping->flags);
+ clear_bit(AS_ENOSPC, &mapping->flags);
+ return err;
+}
+EXPORT_SYMBOL(file_check_and_advance_wb_err);
+
+/**
+ * file_write_and_wait_range - write out & wait on a file range
+ * @file: file pointing to address_space with pages
+ * @lstart: offset in bytes where the range starts
+ * @lend: offset in bytes where the range ends (inclusive)
+ *
+ * Write out and wait upon file offsets lstart->lend, inclusive.
+ *
+ * Note that @lend is inclusive (describes the last byte to be written) so
+ * that this function can be used to write to the very end-of-file (end = -1).
+ *
+ * After writing out and waiting on the data, we check and advance the
+ * f_wb_err cursor to the latest value, and return any errors detected there.
+ */
+int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
+{
+ int err = 0, err2;
+ struct address_space *mapping = file->f_mapping;
+
+ if (mapping_needs_writeback(mapping)) {
+ err = __filemap_fdatawrite_range(mapping, lstart, lend,
+ WB_SYNC_ALL);
+ /* See comment of filemap_write_and_wait() */
+ if (err != -EIO)
+ __filemap_fdatawait_range(mapping, lstart, lend);
+ }
+ err2 = file_check_and_advance_wb_err(file);
+ if (!err)
+ err = err2;
+ return err;
+}
+EXPORT_SYMBOL(file_write_and_wait_range);
+
+/**
+ * replace_page_cache_page - replace a pagecache page with a new one
+ * @old: page to be replaced
+ * @new: page to replace with
+ * @gfp_mask: allocation mode
+ *
+ * This function replaces a page in the pagecache with a new one. On
+ * success it acquires the pagecache reference for the new page and
+ * drops it for the old page. Both the old and new pages must be
+ * locked. This function does not add the new page to the LRU, the
+ * caller must do that.
+ *
+ * The remove + add is atomic. The only way this function can fail is
+ * memory allocation failure.
+ */
+int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
+{
+ int error;
+
+ VM_BUG_ON_PAGE(!PageLocked(old), old);
+ VM_BUG_ON_PAGE(!PageLocked(new), new);
+ VM_BUG_ON_PAGE(new->mapping, new);
+
+ error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK);
+ if (!error) {
+ struct address_space *mapping = old->mapping;
+ void (*freepage)(struct page *);
+ unsigned long flags;
+
+ pgoff_t offset = old->index;
+ freepage = mapping->a_ops->freepage;
+
+ get_page(new);
+ new->mapping = mapping;
+ new->index = offset;
+
+ xa_lock_irqsave(&mapping->i_pages, flags);
+ __delete_from_page_cache(old, NULL);
+ error = page_cache_tree_insert(mapping, new, NULL);
+ BUG_ON(error);
+
+ /*
+ * hugetlb pages do not participate in page cache accounting.
+ */
+ if (!PageHuge(new))
+ __inc_node_page_state(new, NR_FILE_PAGES);
+ if (PageSwapBacked(new))
+ __inc_node_page_state(new, NR_SHMEM);
+ xa_unlock_irqrestore(&mapping->i_pages, flags);
+ mem_cgroup_migrate(old, new);
+ radix_tree_preload_end();
+ if (freepage)
+ freepage(old);
+ put_page(old);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(replace_page_cache_page);
+
+static int __add_to_page_cache_locked(struct page *page,
+ struct address_space *mapping,
+ pgoff_t offset, gfp_t gfp_mask,
+ void **shadowp)
+{
+ int huge = PageHuge(page);
+ struct mem_cgroup *memcg;
+ int error;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(PageSwapBacked(page), page);
+
+ if (!huge) {
+ error = mem_cgroup_try_charge(page, current->mm,
+ gfp_mask, &memcg, false);
+ if (error)
+ return error;
+ }
+
+ error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK);
+ if (error) {
+ if (!huge)
+ mem_cgroup_cancel_charge(page, memcg, false);
+ return error;
+ }
+
+ get_page(page);
+ page->mapping = mapping;
+ page->index = offset;
+
+ xa_lock_irq(&mapping->i_pages);
+ error = page_cache_tree_insert(mapping, page, shadowp);
+ radix_tree_preload_end();
+ if (unlikely(error))
+ goto err_insert;
+
+ /* hugetlb pages do not participate in page cache accounting. */
+ if (!huge)
+ __inc_node_page_state(page, NR_FILE_PAGES);
+ xa_unlock_irq(&mapping->i_pages);
+ if (!huge)
+ mem_cgroup_commit_charge(page, memcg, false, false);
+ trace_mm_filemap_add_to_page_cache(page);
+ return 0;
+err_insert:
+ page->mapping = NULL;
+ /* Leave page->index set: truncation relies upon it */
+ xa_unlock_irq(&mapping->i_pages);
+ if (!huge)
+ mem_cgroup_cancel_charge(page, memcg, false);
+ put_page(page);
+ return error;
+}
+
+/**
+ * add_to_page_cache_locked - add a locked page to the pagecache
+ * @page: page to add
+ * @mapping: the page's address_space
+ * @offset: page index
+ * @gfp_mask: page allocation mode
+ *
+ * This function is used to add a page to the pagecache. It must be locked.
+ * This function does not add the page to the LRU. The caller must do that.
+ */
+int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
+ pgoff_t offset, gfp_t gfp_mask)
+{
+ return __add_to_page_cache_locked(page, mapping, offset,
+ gfp_mask, NULL);
+}
+EXPORT_SYMBOL(add_to_page_cache_locked);
+
+int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
+ pgoff_t offset, gfp_t gfp_mask)
+{
+ void *shadow = NULL;
+ int ret;
+
+ __SetPageLocked(page);
+ ret = __add_to_page_cache_locked(page, mapping, offset,
+ gfp_mask, &shadow);
+ if (unlikely(ret))
+ __ClearPageLocked(page);
+ else {
+ /*
+ * The page might have been evicted from cache only
+ * recently, in which case it should be activated like
+ * any other repeatedly accessed page.
+ * The exception is pages getting rewritten; evicting other
+ * data from the working set, only to cache data that will
+ * get overwritten with something else, is a waste of memory.
+ */
+ if (!(gfp_mask & __GFP_WRITE) &&
+ shadow && workingset_refault(shadow)) {
+ SetPageActive(page);
+ workingset_activation(page);
+ } else
+ ClearPageActive(page);
+ lru_cache_add(page);
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
+
+#ifdef CONFIG_NUMA
+struct page *__page_cache_alloc(gfp_t gfp)
+{
+ int n;
+ struct page *page;
+
+ if (cpuset_do_page_mem_spread()) {
+ unsigned int cpuset_mems_cookie;
+ do {
+ cpuset_mems_cookie = read_mems_allowed_begin();
+ n = cpuset_mem_spread_node();
+ page = __alloc_pages_node(n, gfp, 0);
+ } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
+
+ return page;
+ }
+ return alloc_pages(gfp, 0);
+}
+EXPORT_SYMBOL(__page_cache_alloc);
+#endif
+
+/*
+ * In order to wait for pages to become available there must be
+ * waitqueues associated with pages. By using a hash table of
+ * waitqueues where the bucket discipline is to maintain all
+ * waiters on the same queue and wake all when any of the pages
+ * become available, and for the woken contexts to check to be
+ * sure the appropriate page became available, this saves space
+ * at a cost of "thundering herd" phenomena during rare hash
+ * collisions.
+ */
+#define PAGE_WAIT_TABLE_BITS 8
+#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
+static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
+
+static wait_queue_head_t *page_waitqueue(struct page *page)
+{
+ return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
+}
+
+void __init pagecache_init(void)
+{
+ int i;
+
+ for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
+ init_waitqueue_head(&page_wait_table[i]);
+
+ page_writeback_init();
+}
+
+/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
+struct wait_page_key {
+ struct page *page;
+ int bit_nr;
+ int page_match;
+};
+
+struct wait_page_queue {
+ struct page *page;
+ int bit_nr;
+ wait_queue_entry_t wait;
+};
+
+static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
+{
+ struct wait_page_key *key = arg;
+ struct wait_page_queue *wait_page
+ = container_of(wait, struct wait_page_queue, wait);
+
+ if (wait_page->page != key->page)
+ return 0;
+ key->page_match = 1;
+
+ if (wait_page->bit_nr != key->bit_nr)
+ return 0;
+
+ /* Stop walking if it's locked */
+ if (test_bit(key->bit_nr, &key->page->flags))
+ return -1;
+
+ return autoremove_wake_function(wait, mode, sync, key);
+}
+
+static void wake_up_page_bit(struct page *page, int bit_nr)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ struct wait_page_key key;
+ unsigned long flags;
+ wait_queue_entry_t bookmark;
+
+ key.page = page;
+ key.bit_nr = bit_nr;
+ key.page_match = 0;
+
+ bookmark.flags = 0;
+ bookmark.private = NULL;
+ bookmark.func = NULL;
+ INIT_LIST_HEAD(&bookmark.entry);
+
+ spin_lock_irqsave(&q->lock, flags);
+ __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
+
+ while (bookmark.flags & WQ_FLAG_BOOKMARK) {
+ /*
+ * Take a breather from holding the lock,
+ * allow pages that finish wake up asynchronously
+ * to acquire the lock and remove themselves
+ * from wait queue
+ */
+ spin_unlock_irqrestore(&q->lock, flags);
+ cpu_relax();
+ spin_lock_irqsave(&q->lock, flags);
+ __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
+ }
+
+ /*
+ * It is possible for other pages to have collided on the waitqueue
+ * hash, so in that case check for a page match. That prevents a long-
+ * term waiter
+ *
+ * It is still possible to miss a case here, when we woke page waiters
+ * and removed them from the waitqueue, but there are still other
+ * page waiters.
+ */
+ if (!waitqueue_active(q) || !key.page_match) {
+ ClearPageWaiters(page);
+ /*
+ * It's possible to miss clearing Waiters here, when we woke
+ * our page waiters, but the hashed waitqueue has waiters for
+ * other pages on it.
+ *
+ * That's okay, it's a rare case. The next waker will clear it.
+ */
+ }
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+
+static void wake_up_page(struct page *page, int bit)
+{
+ if (!PageWaiters(page))
+ return;
+ wake_up_page_bit(page, bit);
+}
+
+static inline int wait_on_page_bit_common(wait_queue_head_t *q,
+ struct page *page, int bit_nr, int state, bool lock)
+{
+ struct wait_page_queue wait_page;
+ wait_queue_entry_t *wait = &wait_page.wait;
+ int ret = 0;
+
+ init_wait(wait);
+ wait->flags = lock ? WQ_FLAG_EXCLUSIVE : 0;
+ wait->func = wake_page_function;
+ wait_page.page = page;
+ wait_page.bit_nr = bit_nr;
+
+ for (;;) {
+ spin_lock_irq(&q->lock);
+
+ if (likely(list_empty(&wait->entry))) {
+ __add_wait_queue_entry_tail(q, wait);
+ SetPageWaiters(page);
+ }
+
+ set_current_state(state);
+
+ spin_unlock_irq(&q->lock);
+
+ if (likely(test_bit(bit_nr, &page->flags))) {
+ io_schedule();
+ }
+
+ if (lock) {
+ if (!test_and_set_bit_lock(bit_nr, &page->flags))
+ break;
+ } else {
+ if (!test_bit(bit_nr, &page->flags))
+ break;
+ }
+
+ if (unlikely(signal_pending_state(state, current))) {
+ ret = -EINTR;
+ break;
+ }
+ }
+
+ finish_wait(q, wait);
+
+ /*
+ * A signal could leave PageWaiters set. Clearing it here if
+ * !waitqueue_active would be possible (by open-coding finish_wait),
+ * but still fail to catch it in the case of wait hash collision. We
+ * already can fail to clear wait hash collision cases, so don't
+ * bother with signals either.
+ */
+
+ return ret;
+}
+
+void wait_on_page_bit(struct page *page, int bit_nr)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
+}
+EXPORT_SYMBOL(wait_on_page_bit);
+
+int wait_on_page_bit_killable(struct page *page, int bit_nr)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
+}
+EXPORT_SYMBOL(wait_on_page_bit_killable);
+
+/**
+ * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
+ * @page: Page defining the wait queue of interest
+ * @waiter: Waiter to add to the queue
+ *
+ * Add an arbitrary @waiter to the wait queue for the nominated @page.
+ */
+void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->lock, flags);
+ __add_wait_queue_entry_tail(q, waiter);
+ SetPageWaiters(page);
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL_GPL(add_page_wait_queue);
+
+#ifndef clear_bit_unlock_is_negative_byte
+
+/*
+ * PG_waiters is the high bit in the same byte as PG_lock.
+ *
+ * On x86 (and on many other architectures), we can clear PG_lock and
+ * test the sign bit at the same time. But if the architecture does
+ * not support that special operation, we just do this all by hand
+ * instead.
+ *
+ * The read of PG_waiters has to be after (or concurrently with) PG_locked
+ * being cleared, but a memory barrier should be unneccssary since it is
+ * in the same byte as PG_locked.
+ */
+static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
+{
+ clear_bit_unlock(nr, mem);
+ /* smp_mb__after_atomic(); */
+ return test_bit(PG_waiters, mem);
+}
+
+#endif
+
+/**
+ * unlock_page - unlock a locked page
+ * @page: the page
+ *
+ * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
+ * Also wakes sleepers in wait_on_page_writeback() because the wakeup
+ * mechanism between PageLocked pages and PageWriteback pages is shared.
+ * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
+ *
+ * Note that this depends on PG_waiters being the sign bit in the byte
+ * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
+ * clear the PG_locked bit and test PG_waiters at the same time fairly
+ * portably (architectures that do LL/SC can test any bit, while x86 can
+ * test the sign bit).
+ */
+void unlock_page(struct page *page)
+{
+ BUILD_BUG_ON(PG_waiters != 7);
+ page = compound_head(page);
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
+ wake_up_page_bit(page, PG_locked);
+}
+EXPORT_SYMBOL(unlock_page);
+
+/**
+ * end_page_writeback - end writeback against a page
+ * @page: the page
+ */
+void end_page_writeback(struct page *page)
+{
+ /*
+ * TestClearPageReclaim could be used here but it is an atomic
+ * operation and overkill in this particular case. Failing to
+ * shuffle a page marked for immediate reclaim is too mild to
+ * justify taking an atomic operation penalty at the end of
+ * ever page writeback.
+ */
+ if (PageReclaim(page)) {
+ ClearPageReclaim(page);
+ rotate_reclaimable_page(page);
+ }
+
+ if (!test_clear_page_writeback(page))
+ BUG();
+
+ smp_mb__after_atomic();
+ wake_up_page(page, PG_writeback);
+}
+EXPORT_SYMBOL(end_page_writeback);
+
+/*
+ * After completing I/O on a page, call this routine to update the page
+ * flags appropriately
+ */
+void page_endio(struct page *page, bool is_write, int err)
+{
+ if (!is_write) {
+ if (!err) {
+ SetPageUptodate(page);
+ } else {
+ ClearPageUptodate(page);
+ SetPageError(page);
+ }
+ unlock_page(page);
+ } else {
+ if (err) {
+ struct address_space *mapping;
+
+ SetPageError(page);
+ mapping = page_mapping(page);
+ if (mapping)
+ mapping_set_error(mapping, err);
+ }
+ end_page_writeback(page);
+ }
+}
+EXPORT_SYMBOL_GPL(page_endio);
+
+/**
+ * __lock_page - get a lock on the page, assuming we need to sleep to get it
+ * @__page: the page to lock
+ */
+void __lock_page(struct page *__page)
+{
+ struct page *page = compound_head(__page);
+ wait_queue_head_t *q = page_waitqueue(page);
+ wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
+}
+EXPORT_SYMBOL(__lock_page);
+
+int __lock_page_killable(struct page *__page)
+{
+ struct page *page = compound_head(__page);
+ wait_queue_head_t *q = page_waitqueue(page);
+ return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
+}
+EXPORT_SYMBOL_GPL(__lock_page_killable);
+
+/*
+ * Return values:
+ * 1 - page is locked; mmap_sem is still held.
+ * 0 - page is not locked.
+ * mmap_sem has been released (up_read()), unless flags had both
+ * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
+ * which case mmap_sem is still held.
+ *
+ * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
+ * with the page locked and the mmap_sem unperturbed.
+ */
+int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
+ unsigned int flags)
+{
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ /*
+ * CAUTION! In this case, mmap_sem is not released
+ * even though return 0.
+ */
+ if (flags & FAULT_FLAG_RETRY_NOWAIT)
+ return 0;
+
+ up_read(&mm->mmap_sem);
+ if (flags & FAULT_FLAG_KILLABLE)
+ wait_on_page_locked_killable(page);
+ else
+ wait_on_page_locked(page);
+ return 0;
+ } else {
+ if (flags & FAULT_FLAG_KILLABLE) {
+ int ret;
+
+ ret = __lock_page_killable(page);
+ if (ret) {
+ up_read(&mm->mmap_sem);
+ return 0;
+ }
+ } else
+ __lock_page(page);
+ return 1;
+ }
+}
+
+/**
+ * page_cache_next_hole - find the next hole (not-present entry)
+ * @mapping: mapping
+ * @index: index
+ * @max_scan: maximum range to search
+ *
+ * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
+ * lowest indexed hole.
+ *
+ * Returns: the index of the hole if found, otherwise returns an index
+ * outside of the set specified (in which case 'return - index >=
+ * max_scan' will be true). In rare cases of index wrap-around, 0 will
+ * be returned.
+ *
+ * page_cache_next_hole may be called under rcu_read_lock. However,
+ * like radix_tree_gang_lookup, this will not atomically search a
+ * snapshot of the tree at a single point in time. For example, if a
+ * hole is created at index 5, then subsequently a hole is created at
+ * index 10, page_cache_next_hole covering both indexes may return 10
+ * if called under rcu_read_lock.
+ */
+pgoff_t page_cache_next_hole(struct address_space *mapping,
+ pgoff_t index, unsigned long max_scan)
+{
+ unsigned long i;
+
+ for (i = 0; i < max_scan; i++) {
+ struct page *page;
+
+ page = radix_tree_lookup(&mapping->i_pages, index);
+ if (!page || radix_tree_exceptional_entry(page))
+ break;
+ index++;
+ if (index == 0)
+ break;
+ }
+
+ return index;
+}
+EXPORT_SYMBOL(page_cache_next_hole);
+
+/**
+ * page_cache_prev_hole - find the prev hole (not-present entry)
+ * @mapping: mapping
+ * @index: index
+ * @max_scan: maximum range to search
+ *
+ * Search backwards in the range [max(index-max_scan+1, 0), index] for
+ * the first hole.
+ *
+ * Returns: the index of the hole if found, otherwise returns an index
+ * outside of the set specified (in which case 'index - return >=
+ * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
+ * will be returned.
+ *
+ * page_cache_prev_hole may be called under rcu_read_lock. However,
+ * like radix_tree_gang_lookup, this will not atomically search a
+ * snapshot of the tree at a single point in time. For example, if a
+ * hole is created at index 10, then subsequently a hole is created at
+ * index 5, page_cache_prev_hole covering both indexes may return 5 if
+ * called under rcu_read_lock.
+ */
+pgoff_t page_cache_prev_hole(struct address_space *mapping,
+ pgoff_t index, unsigned long max_scan)
+{
+ unsigned long i;
+
+ for (i = 0; i < max_scan; i++) {
+ struct page *page;
+
+ page = radix_tree_lookup(&mapping->i_pages, index);
+ if (!page || radix_tree_exceptional_entry(page))
+ break;
+ index--;
+ if (index == ULONG_MAX)
+ break;
+ }
+
+ return index;
+}
+EXPORT_SYMBOL(page_cache_prev_hole);
+
+/**
+ * find_get_entry - find and get a page cache entry
+ * @mapping: the address_space to search
+ * @offset: the page cache index
+ *
+ * Looks up the page cache slot at @mapping & @offset. If there is a
+ * page cache page, it is returned with an increased refcount.
+ *
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
+ *
+ * Otherwise, %NULL is returned.
+ */
+struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
+{
+ void **pagep;
+ struct page *head, *page;
+
+ rcu_read_lock();
+repeat:
+ page = NULL;
+ pagep = radix_tree_lookup_slot(&mapping->i_pages, offset);
+ if (pagep) {
+ page = radix_tree_deref_slot(pagep);
+ if (unlikely(!page))
+ goto out;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page))
+ goto repeat;
+ /*
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Return
+ * it without attempting to raise page count.
+ */
+ goto out;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /*
+ * Has the page moved?
+ * This is part of the lockless pagecache protocol. See
+ * include/linux/pagemap.h for details.
+ */
+ if (unlikely(page != *pagep)) {
+ put_page(head);
+ goto repeat;
+ }
+ }
+out:
+ rcu_read_unlock();
+
+ return page;
+}
+EXPORT_SYMBOL(find_get_entry);
+
+/**
+ * find_lock_entry - locate, pin and lock a page cache entry
+ * @mapping: the address_space to search
+ * @offset: the page cache index
+ *
+ * Looks up the page cache slot at @mapping & @offset. If there is a
+ * page cache page, it is returned locked and with an increased
+ * refcount.
+ *
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
+ *
+ * Otherwise, %NULL is returned.
+ *
+ * find_lock_entry() may sleep.
+ */
+struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
+{
+ struct page *page;
+
+repeat:
+ page = find_get_entry(mapping, offset);
+ if (page && !radix_tree_exception(page)) {
+ lock_page(page);
+ /* Has the page been truncated? */
+ if (unlikely(page_mapping(page) != mapping)) {
+ unlock_page(page);
+ put_page(page);
+ goto repeat;
+ }
+ VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
+ }
+ return page;
+}
+EXPORT_SYMBOL(find_lock_entry);
+
+/**
+ * pagecache_get_page - find and get a page reference
+ * @mapping: the address_space to search
+ * @offset: the page index
+ * @fgp_flags: PCG flags
+ * @gfp_mask: gfp mask to use for the page cache data page allocation
+ *
+ * Looks up the page cache slot at @mapping & @offset.
+ *
+ * PCG flags modify how the page is returned.
+ *
+ * @fgp_flags can be:
+ *
+ * - FGP_ACCESSED: the page will be marked accessed
+ * - FGP_LOCK: Page is return locked
+ * - FGP_CREAT: If page is not present then a new page is allocated using
+ * @gfp_mask and added to the page cache and the VM's LRU
+ * list. The page is returned locked and with an increased
+ * refcount. Otherwise, NULL is returned.
+ *
+ * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
+ * if the GFP flags specified for FGP_CREAT are atomic.
+ *
+ * If there is a page cache page, it is returned with an increased refcount.
+ */
+struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
+ int fgp_flags, gfp_t gfp_mask)
+{
+ struct page *page;
+
+repeat:
+ page = find_get_entry(mapping, offset);
+ if (radix_tree_exceptional_entry(page))
+ page = NULL;
+ if (!page)
+ goto no_page;
+
+ if (fgp_flags & FGP_LOCK) {
+ if (fgp_flags & FGP_NOWAIT) {
+ if (!trylock_page(page)) {
+ put_page(page);
+ return NULL;
+ }
+ } else {
+ lock_page(page);
+ }
+
+ /* Has the page been truncated? */
+ if (unlikely(page->mapping != mapping)) {
+ unlock_page(page);
+ put_page(page);
+ goto repeat;
+ }
+ VM_BUG_ON_PAGE(page->index != offset, page);
+ }
+
+ if (page && (fgp_flags & FGP_ACCESSED))
+ mark_page_accessed(page);
+
+no_page:
+ if (!page && (fgp_flags & FGP_CREAT)) {
+ int err;
+ if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
+ gfp_mask |= __GFP_WRITE;
+ if (fgp_flags & FGP_NOFS)
+ gfp_mask &= ~__GFP_FS;
+
+ page = __page_cache_alloc(gfp_mask);
+ if (!page)
+ return NULL;
+
+ if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
+ fgp_flags |= FGP_LOCK;
+
+ /* Init accessed so avoid atomic mark_page_accessed later */
+ if (fgp_flags & FGP_ACCESSED)
+ __SetPageReferenced(page);
+
+ err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
+ if (unlikely(err)) {
+ put_page(page);
+ page = NULL;
+ if (err == -EEXIST)
+ goto repeat;
+ }
+ }
+
+ return page;
+}
+EXPORT_SYMBOL(pagecache_get_page);
+
+/**
+ * find_get_entries - gang pagecache lookup
+ * @mapping: The address_space to search
+ * @start: The starting page cache index
+ * @nr_entries: The maximum number of entries
+ * @entries: Where the resulting entries are placed
+ * @indices: The cache indices corresponding to the entries in @entries
+ *
+ * find_get_entries() will search for and return a group of up to
+ * @nr_entries entries in the mapping. The entries are placed at
+ * @entries. find_get_entries() takes a reference against any actual
+ * pages it returns.
+ *
+ * The search returns a group of mapping-contiguous page cache entries
+ * with ascending indexes. There may be holes in the indices due to
+ * not-present pages.
+ *
+ * Any shadow entries of evicted pages, or swap entries from
+ * shmem/tmpfs, are included in the returned array.
+ *
+ * find_get_entries() returns the number of pages and shadow entries
+ * which were found.
+ */
+unsigned find_get_entries(struct address_space *mapping,
+ pgoff_t start, unsigned int nr_entries,
+ struct page **entries, pgoff_t *indices)
+{
+ void **slot;
+ unsigned int ret = 0;
+ struct radix_tree_iter iter;
+
+ if (!nr_entries)
+ return 0;
+
+ rcu_read_lock();
+ radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
+ struct page *head, *page;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ continue;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ /*
+ * A shadow entry of a recently evicted page, a swap
+ * entry from shmem/tmpfs or a DAX entry. Return it
+ * without attempting to raise page count.
+ */
+ goto export;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+export:
+ indices[ret] = iter.index;
+ entries[ret] = page;
+ if (++ret == nr_entries)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+/**
+ * find_get_pages_range - gang pagecache lookup
+ * @mapping: The address_space to search
+ * @start: The starting page index
+ * @end: The final page index (inclusive)
+ * @nr_pages: The maximum number of pages
+ * @pages: Where the resulting pages are placed
+ *
+ * find_get_pages_range() will search for and return a group of up to @nr_pages
+ * pages in the mapping starting at index @start and up to index @end
+ * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
+ * a reference against the returned pages.
+ *
+ * The search returns a group of mapping-contiguous pages with ascending
+ * indexes. There may be holes in the indices due to not-present pages.
+ * We also update @start to index the next page for the traversal.
+ *
+ * find_get_pages_range() returns the number of pages which were found. If this
+ * number is smaller than @nr_pages, the end of specified range has been
+ * reached.
+ */
+unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
+ pgoff_t end, unsigned int nr_pages,
+ struct page **pages)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
+
+ rcu_read_lock();
+ radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, *start) {
+ struct page *head, *page;
+
+ if (iter.index > end)
+ break;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ continue;
+
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ /*
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Skip
+ * over it.
+ */
+ continue;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+
+ pages[ret] = page;
+ if (++ret == nr_pages) {
+ *start = pages[ret - 1]->index + 1;
+ goto out;
+ }
+ }
+
+ /*
+ * We come here when there is no page beyond @end. We take care to not
+ * overflow the index @start as it confuses some of the callers. This
+ * breaks the iteration when there is page at index -1 but that is
+ * already broken anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *start = (pgoff_t)-1;
+ else
+ *start = end + 1;
+out:
+ rcu_read_unlock();
+
+ return ret;
+}
+
+/**
+ * find_get_pages_contig - gang contiguous pagecache lookup
+ * @mapping: The address_space to search
+ * @index: The starting page index
+ * @nr_pages: The maximum number of pages
+ * @pages: Where the resulting pages are placed
+ *
+ * find_get_pages_contig() works exactly like find_get_pages(), except
+ * that the returned number of pages are guaranteed to be contiguous.
+ *
+ * find_get_pages_contig() returns the number of pages which were found.
+ */
+unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
+ unsigned int nr_pages, struct page **pages)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned int ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
+
+ rcu_read_lock();
+ radix_tree_for_each_contig(slot, &mapping->i_pages, &iter, index) {
+ struct page *head, *page;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ /* The hole, there no reason to continue */
+ if (unlikely(!page))
+ break;
+
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ /*
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Stop
+ * looking for contiguous pages.
+ */
+ break;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /*
+ * must check mapping and index after taking the ref.
+ * otherwise we can get both false positives and false
+ * negatives, which is just confusing to the caller.
+ */
+ if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
+ put_page(page);
+ break;
+ }
+
+ pages[ret] = page;
+ if (++ret == nr_pages)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(find_get_pages_contig);
+
+/**
+ * find_get_pages_range_tag - find and return pages in given range matching @tag
+ * @mapping: the address_space to search
+ * @index: the starting page index
+ * @end: The final page index (inclusive)
+ * @tag: the tag index
+ * @nr_pages: the maximum number of pages
+ * @pages: where the resulting pages are placed
+ *
+ * Like find_get_pages, except we only return pages which are tagged with
+ * @tag. We update @index to index the next page for the traversal.
+ */
+unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
+ pgoff_t end, int tag, unsigned int nr_pages,
+ struct page **pages)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ unsigned ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
+
+ rcu_read_lock();
+ radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, *index, tag) {
+ struct page *head, *page;
+
+ if (iter.index > end)
+ break;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ continue;
+
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ /*
+ * A shadow entry of a recently evicted page.
+ *
+ * Those entries should never be tagged, but
+ * this tree walk is lockless and the tags are
+ * looked up in bulk, one radix tree node at a
+ * time, so there is a sizable window for page
+ * reclaim to evict a page we saw tagged.
+ *
+ * Skip over it.
+ */
+ continue;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+
+ pages[ret] = page;
+ if (++ret == nr_pages) {
+ *index = pages[ret - 1]->index + 1;
+ goto out;
+ }
+ }
+
+ /*
+ * We come here when we got at @end. We take care to not overflow the
+ * index @index as it confuses some of the callers. This breaks the
+ * iteration when there is page at index -1 but that is already broken
+ * anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *index = (pgoff_t)-1;
+ else
+ *index = end + 1;
+out:
+ rcu_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL(find_get_pages_range_tag);
+
+/**
+ * find_get_entries_tag - find and return entries that match @tag
+ * @mapping: the address_space to search
+ * @start: the starting page cache index
+ * @tag: the tag index
+ * @nr_entries: the maximum number of entries
+ * @entries: where the resulting entries are placed
+ * @indices: the cache indices corresponding to the entries in @entries
+ *
+ * Like find_get_entries, except we only return entries which are tagged with
+ * @tag.
+ */
+unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
+ int tag, unsigned int nr_entries,
+ struct page **entries, pgoff_t *indices)
+{
+ void **slot;
+ unsigned int ret = 0;
+ struct radix_tree_iter iter;
+
+ if (!nr_entries)
+ return 0;
+
+ rcu_read_lock();
+ radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start, tag) {
+ struct page *head, *page;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ continue;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+
+ /*
+ * A shadow entry of a recently evicted page, a swap
+ * entry from shmem/tmpfs or a DAX entry. Return it
+ * without attempting to raise page count.
+ */
+ goto export;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+export:
+ indices[ret] = iter.index;
+ entries[ret] = page;
+ if (++ret == nr_entries)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(find_get_entries_tag);
+
+/*
+ * CD/DVDs are error prone. When a medium error occurs, the driver may fail
+ * a _large_ part of the i/o request. Imagine the worst scenario:
+ *
+ * ---R__________________________________________B__________
+ * ^ reading here ^ bad block(assume 4k)
+ *
+ * read(R) => miss => readahead(R...B) => media error => frustrating retries
+ * => failing the whole request => read(R) => read(R+1) =>
+ * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
+ * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
+ * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
+ *
+ * It is going insane. Fix it by quickly scaling down the readahead size.
+ */
+static void shrink_readahead_size_eio(struct file *filp,
+ struct file_ra_state *ra)
+{
+ ra->ra_pages /= 4;
+}
+
+/**
+ * generic_file_buffered_read - generic file read routine
+ * @iocb: the iocb to read
+ * @iter: data destination
+ * @written: already copied
+ *
+ * This is a generic file read routine, and uses the
+ * mapping->a_ops->readpage() function for the actual low-level stuff.
+ *
+ * This is really ugly. But the goto's actually try to clarify some
+ * of the logic when it comes to error handling etc.
+ */
+static ssize_t generic_file_buffered_read(struct kiocb *iocb,
+ struct iov_iter *iter, ssize_t written)
+{
+ struct file *filp = iocb->ki_filp;
+ struct address_space *mapping = filp->f_mapping;
+ struct inode *inode = mapping->host;
+ struct file_ra_state *ra = &filp->f_ra;
+ loff_t *ppos = &iocb->ki_pos;
+ pgoff_t index;
+ pgoff_t last_index;
+ pgoff_t prev_index;
+ unsigned long offset; /* offset into pagecache page */
+ unsigned int prev_offset;
+ int error = 0;
+
+ if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
+ return 0;
+ iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
+
+ index = *ppos >> PAGE_SHIFT;
+ prev_index = ra->prev_pos >> PAGE_SHIFT;
+ prev_offset = ra->prev_pos & (PAGE_SIZE-1);
+ last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
+ offset = *ppos & ~PAGE_MASK;
+
+ for (;;) {
+ struct page *page;
+ pgoff_t end_index;
+ loff_t isize;
+ unsigned long nr, ret;
+
+ cond_resched();
+find_page:
+ if (fatal_signal_pending(current)) {
+ error = -EINTR;
+ goto out;
+ }
+
+ page = find_get_page(mapping, index);
+ if (!page) {
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ goto would_block;
+ page_cache_sync_readahead(mapping,
+ ra, filp,
+ index, last_index - index);
+ page = find_get_page(mapping, index);
+ if (unlikely(page == NULL))
+ goto no_cached_page;
+ }
+ if (PageReadahead(page)) {
+ page_cache_async_readahead(mapping,
+ ra, filp, page,
+ index, last_index - index);
+ }
+ if (!PageUptodate(page)) {
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ put_page(page);
+ goto would_block;
+ }
+
+ /*
+ * See comment in do_read_cache_page on why
+ * wait_on_page_locked is used to avoid unnecessarily
+ * serialisations and why it's safe.
+ */
+ error = wait_on_page_locked_killable(page);
+ if (unlikely(error))
+ goto readpage_error;
+ if (PageUptodate(page))
+ goto page_ok;
+
+ if (inode->i_blkbits == PAGE_SHIFT ||
+ !mapping->a_ops->is_partially_uptodate)
+ goto page_not_up_to_date;
+ /* pipes can't handle partially uptodate pages */
+ if (unlikely(iter->type & ITER_PIPE))
+ goto page_not_up_to_date;
+ if (!trylock_page(page))
+ goto page_not_up_to_date;
+ /* Did it get truncated before we got the lock? */
+ if (!page->mapping)
+ goto page_not_up_to_date_locked;
+ if (!mapping->a_ops->is_partially_uptodate(page,
+ offset, iter->count))
+ goto page_not_up_to_date_locked;
+ unlock_page(page);
+ }
+page_ok:
+ /*
+ * i_size must be checked after we know the page is Uptodate.
+ *
+ * Checking i_size after the check allows us to calculate
+ * the correct value for "nr", which means the zero-filled
+ * part of the page is not copied back to userspace (unless
+ * another truncate extends the file - this is desired though).
+ */
+
+ isize = i_size_read(inode);
+ end_index = (isize - 1) >> PAGE_SHIFT;
+ if (unlikely(!isize || index > end_index)) {
+ put_page(page);
+ goto out;
+ }
+
+ /* nr is the maximum number of bytes to copy from this page */
+ nr = PAGE_SIZE;
+ if (index == end_index) {
+ nr = ((isize - 1) & ~PAGE_MASK) + 1;
+ if (nr <= offset) {
+ put_page(page);
+ goto out;
+ }
+ }
+ nr = nr - offset;
+
+ /* If users can be writing to this page using arbitrary
+ * virtual addresses, take care about potential aliasing
+ * before reading the page on the kernel side.
+ */
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_page(page);
+
+ /*
+ * When a sequential read accesses a page several times,
+ * only mark it as accessed the first time.
+ */
+ if (prev_index != index || offset != prev_offset)
+ mark_page_accessed(page);
+ prev_index = index;
+
+ /*
+ * Ok, we have the page, and it's up-to-date, so
+ * now we can copy it to user space...
+ */
+
+ ret = copy_page_to_iter(page, offset, nr, iter);
+ offset += ret;
+ index += offset >> PAGE_SHIFT;
+ offset &= ~PAGE_MASK;
+ prev_offset = offset;
+
+ put_page(page);
+ written += ret;
+ if (!iov_iter_count(iter))
+ goto out;
+ if (ret < nr) {
+ error = -EFAULT;
+ goto out;
+ }
+ continue;
+
+page_not_up_to_date:
+ /* Get exclusive access to the page ... */
+ error = lock_page_killable(page);
+ if (unlikely(error))
+ goto readpage_error;
+
+page_not_up_to_date_locked:
+ /* Did it get truncated before we got the lock? */
+ if (!page->mapping) {
+ unlock_page(page);
+ put_page(page);
+ continue;
+ }
+
+ /* Did somebody else fill it already? */
+ if (PageUptodate(page)) {
+ unlock_page(page);
+ goto page_ok;
+ }
+
+readpage:
+ /*
+ * A previous I/O error may have been due to temporary
+ * failures, eg. multipath errors.
+ * PG_error will be set again if readpage fails.
+ */
+ ClearPageError(page);
+ /* Start the actual read. The read will unlock the page. */
+ error = mapping->a_ops->readpage(filp, page);
+
+ if (unlikely(error)) {
+ if (error == AOP_TRUNCATED_PAGE) {
+ put_page(page);
+ error = 0;
+ goto find_page;
+ }
+ goto readpage_error;
+ }
+
+ if (!PageUptodate(page)) {
+ error = lock_page_killable(page);
+ if (unlikely(error))
+ goto readpage_error;
+ if (!PageUptodate(page)) {
+ if (page->mapping == NULL) {
+ /*
+ * invalidate_mapping_pages got it
+ */
+ unlock_page(page);
+ put_page(page);
+ goto find_page;
+ }
+ unlock_page(page);
+ shrink_readahead_size_eio(filp, ra);
+ error = -EIO;
+ goto readpage_error;
+ }
+ unlock_page(page);
+ }
+
+ goto page_ok;
+
+readpage_error:
+ /* UHHUH! A synchronous read error occurred. Report it */
+ put_page(page);
+ goto out;
+
+no_cached_page:
+ /*
+ * Ok, it wasn't cached, so we need to create a new
+ * page..
+ */
+ page = page_cache_alloc(mapping);
+ if (!page) {
+ error = -ENOMEM;
+ goto out;
+ }
+ error = add_to_page_cache_lru(page, mapping, index,
+ mapping_gfp_constraint(mapping, GFP_KERNEL));
+ if (error) {
+ put_page(page);
+ if (error == -EEXIST) {
+ error = 0;
+ goto find_page;
+ }
+ goto out;
+ }
+ goto readpage;
+ }
+
+would_block:
+ error = -EAGAIN;
+out:
+ ra->prev_pos = prev_index;
+ ra->prev_pos <<= PAGE_SHIFT;
+ ra->prev_pos |= prev_offset;
+
+ *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
+ file_accessed(filp);
+ return written ? written : error;
+}
+
+/**
+ * generic_file_read_iter - generic filesystem read routine
+ * @iocb: kernel I/O control block
+ * @iter: destination for the data read
+ *
+ * This is the "read_iter()" routine for all filesystems
+ * that can use the page cache directly.
+ */
+ssize_t
+generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+ size_t count = iov_iter_count(iter);
+ ssize_t retval = 0;
+
+ if (!count)
+ goto out; /* skip atime */
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ loff_t size;
+
+ size = i_size_read(inode);
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (filemap_range_has_page(mapping, iocb->ki_pos,
+ iocb->ki_pos + count - 1))
+ return -EAGAIN;
+ } else {
+ retval = filemap_write_and_wait_range(mapping,
+ iocb->ki_pos,
+ iocb->ki_pos + count - 1);
+ if (retval < 0)
+ goto out;
+ }
+
+ file_accessed(file);
+
+ retval = mapping->a_ops->direct_IO(iocb, iter);
+ if (retval >= 0) {
+ iocb->ki_pos += retval;
+ count -= retval;
+ }
+ iov_iter_revert(iter, count - iov_iter_count(iter));
+
+ /*
+ * Btrfs can have a short DIO read if we encounter
+ * compressed extents, so if there was an error, or if
+ * we've already read everything we wanted to, or if
+ * there was a short read because we hit EOF, go ahead
+ * and return. Otherwise fallthrough to buffered io for
+ * the rest of the read. Buffered reads will not work for
+ * DAX files, so don't bother trying.
+ */
+ if (retval < 0 || !count || iocb->ki_pos >= size ||
+ IS_DAX(inode))
+ goto out;
+ }
+
+ retval = generic_file_buffered_read(iocb, iter, retval);
+out:
+ return retval;
+}
+EXPORT_SYMBOL(generic_file_read_iter);
+
+#ifdef CONFIG_MMU
+/**
+ * page_cache_read - adds requested page to the page cache if not already there
+ * @file: file to read
+ * @offset: page index
+ * @gfp_mask: memory allocation flags
+ *
+ * This adds the requested page to the page cache if it isn't already there,
+ * and schedules an I/O to read in its contents from disk.
+ */
+static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
+{
+ struct address_space *mapping = file->f_mapping;
+ struct page *page;
+ int ret;
+
+ do {
+ page = __page_cache_alloc(gfp_mask);
+ if (!page)
+ return -ENOMEM;
+
+ ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
+ if (ret == 0)
+ ret = mapping->a_ops->readpage(file, page);
+ else if (ret == -EEXIST)
+ ret = 0; /* losing race to add is OK */
+
+ put_page(page);
+
+ } while (ret == AOP_TRUNCATED_PAGE);
+
+ return ret;
+}
+
+#define MMAP_LOTSAMISS (100)
+
+/*
+ * Synchronous readahead happens when we don't even find
+ * a page in the page cache at all.
+ */
+static void do_sync_mmap_readahead(struct vm_area_struct *vma,
+ struct file_ra_state *ra,
+ struct file *file,
+ pgoff_t offset)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ /* If we don't want any read-ahead, don't bother */
+ if (vma->vm_flags & VM_RAND_READ)
+ return;
+ if (!ra->ra_pages)
+ return;
+
+ if (vma->vm_flags & VM_SEQ_READ) {
+ page_cache_sync_readahead(mapping, ra, file, offset,
+ ra->ra_pages);
+ return;
+ }
+
+ /* Avoid banging the cache line if not needed */
+ if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
+ ra->mmap_miss++;
+
+ /*
+ * Do we miss much more than hit in this file? If so,
+ * stop bothering with read-ahead. It will only hurt.
+ */
+ if (ra->mmap_miss > MMAP_LOTSAMISS)
+ return;
+
+ /*
+ * mmap read-around
+ */
+ ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
+ ra->size = ra->ra_pages;
+ ra->async_size = ra->ra_pages / 4;
+ ra_submit(ra, mapping, file);
+}
+
+/*
+ * Asynchronous readahead happens when we find the page and PG_readahead,
+ * so we want to possibly extend the readahead further..
+ */
+static void do_async_mmap_readahead(struct vm_area_struct *vma,
+ struct file_ra_state *ra,
+ struct file *file,
+ struct page *page,
+ pgoff_t offset)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ /* If we don't want any read-ahead, don't bother */
+ if (vma->vm_flags & VM_RAND_READ)
+ return;
+ if (ra->mmap_miss > 0)
+ ra->mmap_miss--;
+ if (PageReadahead(page))
+ page_cache_async_readahead(mapping, ra, file,
+ page, offset, ra->ra_pages);
+}
+
+/**
+ * filemap_fault - read in file data for page fault handling
+ * @vmf: struct vm_fault containing details of the fault
+ *
+ * filemap_fault() is invoked via the vma operations vector for a
+ * mapped memory region to read in file data during a page fault.
+ *
+ * The goto's are kind of ugly, but this streamlines the normal case of having
+ * it in the page cache, and handles the special cases reasonably without
+ * having a lot of duplicated code.
+ *
+ * vma->vm_mm->mmap_sem must be held on entry.
+ *
+ * If our return value has VM_FAULT_RETRY set, it's because
+ * lock_page_or_retry() returned 0.
+ * The mmap_sem has usually been released in this case.
+ * See __lock_page_or_retry() for the exception.
+ *
+ * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
+ * has not been released.
+ *
+ * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
+ */
+vm_fault_t filemap_fault(struct vm_fault *vmf)
+{
+ int error;
+ struct file *file = vmf->vma->vm_file;
+ struct address_space *mapping = file->f_mapping;
+ struct file_ra_state *ra = &file->f_ra;
+ struct inode *inode = mapping->host;
+ pgoff_t offset = vmf->pgoff;
+ pgoff_t max_off;
+ struct page *page;
+ vm_fault_t ret = 0;
+
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(offset >= max_off))
+ return VM_FAULT_SIGBUS;
+
+ /*
+ * Do we have something in the page cache already?
+ */
+ page = find_get_page(mapping, offset);
+ if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
+ /*
+ * We found the page, so try async readahead before
+ * waiting for the lock.
+ */
+ do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
+ } else if (!page) {
+ /* No page in the page cache at all */
+ do_sync_mmap_readahead(vmf->vma, ra, file, offset);
+ count_vm_event(PGMAJFAULT);
+ count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
+ ret = VM_FAULT_MAJOR;
+retry_find:
+ page = find_get_page(mapping, offset);
+ if (!page)
+ goto no_cached_page;
+ }
+
+ if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
+ put_page(page);
+ return ret | VM_FAULT_RETRY;
+ }
+
+ /* Did it get truncated? */
+ if (unlikely(page->mapping != mapping)) {
+ unlock_page(page);
+ put_page(page);
+ goto retry_find;
+ }
+ VM_BUG_ON_PAGE(page->index != offset, page);
+
+ /*
+ * We have a locked page in the page cache, now we need to check
+ * that it's up-to-date. If not, it is going to be due to an error.
+ */
+ if (unlikely(!PageUptodate(page)))
+ goto page_not_uptodate;
+
+ /*
+ * Found the page and have a reference on it.
+ * We must recheck i_size under page lock.
+ */
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(offset >= max_off)) {
+ unlock_page(page);
+ put_page(page);
+ return VM_FAULT_SIGBUS;
+ }
+
+ vmf->page = page;
+ return ret | VM_FAULT_LOCKED;
+
+no_cached_page:
+ /*
+ * We're only likely to ever get here if MADV_RANDOM is in
+ * effect.
+ */
+ error = page_cache_read(file, offset, vmf->gfp_mask);
+
+ /*
+ * The page we want has now been added to the page cache.
+ * In the unlikely event that someone removed it in the
+ * meantime, we'll just come back here and read it again.
+ */
+ if (error >= 0)
+ goto retry_find;
+
+ /*
+ * An error return from page_cache_read can result if the
+ * system is low on memory, or a problem occurs while trying
+ * to schedule I/O.
+ */
+ if (error == -ENOMEM)
+ return VM_FAULT_OOM;
+ return VM_FAULT_SIGBUS;
+
+page_not_uptodate:
+ /*
+ * Umm, take care of errors if the page isn't up-to-date.
+ * Try to re-read it _once_. We do this synchronously,
+ * because there really aren't any performance issues here
+ * and we need to check for errors.
+ */
+ ClearPageError(page);
+ error = mapping->a_ops->readpage(file, page);
+ if (!error) {
+ wait_on_page_locked(page);
+ if (!PageUptodate(page))
+ error = -EIO;
+ }
+ put_page(page);
+
+ if (!error || error == AOP_TRUNCATED_PAGE)
+ goto retry_find;
+
+ /* Things didn't work out. Return zero to tell the mm layer so. */
+ shrink_readahead_size_eio(file, ra);
+ return VM_FAULT_SIGBUS;
+}
+EXPORT_SYMBOL(filemap_fault);
+
+void filemap_map_pages(struct vm_fault *vmf,
+ pgoff_t start_pgoff, pgoff_t end_pgoff)
+{
+ struct radix_tree_iter iter;
+ void **slot;
+ struct file *file = vmf->vma->vm_file;
+ struct address_space *mapping = file->f_mapping;
+ pgoff_t last_pgoff = start_pgoff;
+ unsigned long max_idx;
+ struct page *head, *page;
+
+ rcu_read_lock();
+ radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start_pgoff) {
+ if (iter.index > end_pgoff)
+ break;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ goto next;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ goto next;
+ }
+
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;
+
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ put_page(head);
+ goto repeat;
+ }
+
+ if (!PageUptodate(page) ||
+ PageReadahead(page) ||
+ PageHWPoison(page))
+ goto skip;
+ if (!trylock_page(page))
+ goto skip;
+
+ if (page->mapping != mapping || !PageUptodate(page))
+ goto unlock;
+
+ max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+ if (page->index >= max_idx)
+ goto unlock;
+
+ if (file->f_ra.mmap_miss > 0)
+ file->f_ra.mmap_miss--;
+
+ vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
+ if (vmf->pte)
+ vmf->pte += iter.index - last_pgoff;
+ last_pgoff = iter.index;
+ if (alloc_set_pte(vmf, NULL, page))
+ goto unlock;
+ unlock_page(page);
+ goto next;
+unlock:
+ unlock_page(page);
+skip:
+ put_page(page);
+next:
+ /* Huge page is mapped? No need to proceed. */
+ if (pmd_trans_huge(*vmf->pmd))
+ break;
+ if (iter.index == end_pgoff)
+ break;
+ }
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(filemap_map_pages);
+
+vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ struct page *page = vmf->page;
+ struct inode *inode = file_inode(vmf->vma->vm_file);
+ vm_fault_t ret = VM_FAULT_LOCKED;
+
+ sb_start_pagefault(inode->i_sb);
+ file_update_time(vmf->vma->vm_file);
+ lock_page(page);
+ if (page->mapping != inode->i_mapping) {
+ unlock_page(page);
+ ret = VM_FAULT_NOPAGE;
+ goto out;
+ }
+ /*
+ * We mark the page dirty already here so that when freeze is in
+ * progress, we are guaranteed that writeback during freezing will
+ * see the dirty page and writeprotect it again.
+ */
+ set_page_dirty(page);
+ wait_for_stable_page(page);
+out:
+ sb_end_pagefault(inode->i_sb);
+ return ret;
+}
+
+const struct vm_operations_struct generic_file_vm_ops = {
+ .fault = filemap_fault,
+ .map_pages = filemap_map_pages,
+ .page_mkwrite = filemap_page_mkwrite,
+};
+
+/* This is used for a general mmap of a disk file */
+
+int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ if (!mapping->a_ops->readpage)
+ return -ENOEXEC;
+ file_accessed(file);
+ vma->vm_ops = &generic_file_vm_ops;
+ return 0;
+}
+
+/*
+ * This is for filesystems which do not implement ->writepage.
+ */
+int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+ return -EINVAL;
+ return generic_file_mmap(file, vma);
+}
+#else
+int filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ return -ENOSYS;
+}
+int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
+{
+ return -ENOSYS;
+}
+int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
+{
+ return -ENOSYS;
+}
+#endif /* CONFIG_MMU */
+
+EXPORT_SYMBOL(filemap_page_mkwrite);
+EXPORT_SYMBOL(generic_file_mmap);
+EXPORT_SYMBOL(generic_file_readonly_mmap);
+
+static struct page *wait_on_page_read(struct page *page)
+{
+ if (!IS_ERR(page)) {
+ wait_on_page_locked(page);
+ if (!PageUptodate(page)) {
+ put_page(page);
+ page = ERR_PTR(-EIO);
+ }
+ }
+ return page;
+}
+
+static struct page *do_read_cache_page(struct address_space *mapping,
+ pgoff_t index,
+ int (*filler)(void *, struct page *),
+ void *data,
+ gfp_t gfp)
+{
+ struct page *page;
+ int err;
+repeat:
+ page = find_get_page(mapping, index);
+ if (!page) {
+ page = __page_cache_alloc(gfp);
+ if (!page)
+ return ERR_PTR(-ENOMEM);
+ err = add_to_page_cache_lru(page, mapping, index, gfp);
+ if (unlikely(err)) {
+ put_page(page);
+ if (err == -EEXIST)
+ goto repeat;
+ /* Presumably ENOMEM for radix tree node */
+ return ERR_PTR(err);
+ }
+
+filler:
+ err = filler(data, page);
+ if (err < 0) {
+ put_page(page);
+ return ERR_PTR(err);
+ }
+
+ page = wait_on_page_read(page);
+ if (IS_ERR(page))
+ return page;
+ goto out;
+ }
+ if (PageUptodate(page))
+ goto out;
+
+ /*
+ * Page is not up to date and may be locked due one of the following
+ * case a: Page is being filled and the page lock is held
+ * case b: Read/write error clearing the page uptodate status
+ * case c: Truncation in progress (page locked)
+ * case d: Reclaim in progress
+ *
+ * Case a, the page will be up to date when the page is unlocked.
+ * There is no need to serialise on the page lock here as the page
+ * is pinned so the lock gives no additional protection. Even if the
+ * the page is truncated, the data is still valid if PageUptodate as
+ * it's a race vs truncate race.
+ * Case b, the page will not be up to date
+ * Case c, the page may be truncated but in itself, the data may still
+ * be valid after IO completes as it's a read vs truncate race. The
+ * operation must restart if the page is not uptodate on unlock but
+ * otherwise serialising on page lock to stabilise the mapping gives
+ * no additional guarantees to the caller as the page lock is
+ * released before return.
+ * Case d, similar to truncation. If reclaim holds the page lock, it
+ * will be a race with remove_mapping that determines if the mapping
+ * is valid on unlock but otherwise the data is valid and there is
+ * no need to serialise with page lock.
+ *
+ * As the page lock gives no additional guarantee, we optimistically
+ * wait on the page to be unlocked and check if it's up to date and
+ * use the page if it is. Otherwise, the page lock is required to
+ * distinguish between the different cases. The motivation is that we
+ * avoid spurious serialisations and wakeups when multiple processes
+ * wait on the same page for IO to complete.
+ */
+ wait_on_page_locked(page);
+ if (PageUptodate(page))
+ goto out;
+
+ /* Distinguish between all the cases under the safety of the lock */
+ lock_page(page);
+
+ /* Case c or d, restart the operation */
+ if (!page->mapping) {
+ unlock_page(page);
+ put_page(page);
+ goto repeat;
+ }
+
+ /* Someone else locked and filled the page in a very small window */
+ if (PageUptodate(page)) {
+ unlock_page(page);
+ goto out;
+ }
+ goto filler;
+
+out:
+ mark_page_accessed(page);
+ return page;
+}
+
+/**
+ * read_cache_page - read into page cache, fill it if needed
+ * @mapping: the page's address_space
+ * @index: the page index
+ * @filler: function to perform the read
+ * @data: first arg to filler(data, page) function, often left as NULL
+ *
+ * Read into the page cache. If a page already exists, and PageUptodate() is
+ * not set, try to fill the page and wait for it to become unlocked.
+ *
+ * If the page does not get brought uptodate, return -EIO.
+ */
+struct page *read_cache_page(struct address_space *mapping,
+ pgoff_t index,
+ int (*filler)(void *, struct page *),
+ void *data)
+{
+ return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
+}
+EXPORT_SYMBOL(read_cache_page);
+
+/**
+ * read_cache_page_gfp - read into page cache, using specified page allocation flags.
+ * @mapping: the page's address_space
+ * @index: the page index
+ * @gfp: the page allocator flags to use if allocating
+ *
+ * This is the same as "read_mapping_page(mapping, index, NULL)", but with
+ * any new page allocations done using the specified allocation flags.
+ *
+ * If the page does not get brought uptodate, return -EIO.
+ */
+struct page *read_cache_page_gfp(struct address_space *mapping,
+ pgoff_t index,
+ gfp_t gfp)
+{
+ filler_t *filler = (filler_t *)mapping->a_ops->readpage;
+
+ return do_read_cache_page(mapping, index, filler, NULL, gfp);
+}
+EXPORT_SYMBOL(read_cache_page_gfp);
+
+/*
+ * Performs necessary checks before doing a write
+ *
+ * Can adjust writing position or amount of bytes to write.
+ * Returns appropriate error code that caller should return or
+ * zero in case that write should be allowed.
+ */
+inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ unsigned long limit = rlimit(RLIMIT_FSIZE);
+ loff_t pos;
+
+ if (!iov_iter_count(from))
+ return 0;
+
+ /* FIXME: this is for backwards compatibility with 2.4 */
+ if (iocb->ki_flags & IOCB_APPEND)
+ iocb->ki_pos = i_size_read(inode);
+
+ pos = iocb->ki_pos;
+
+ if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
+ return -EINVAL;
+
+ if (limit != RLIM_INFINITY) {
+ if (iocb->ki_pos >= limit) {
+ send_sig(SIGXFSZ, current, 0);
+ return -EFBIG;
+ }
+ iov_iter_truncate(from, limit - (unsigned long)pos);
+ }
+
+ /*
+ * LFS rule
+ */
+ if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
+ !(file->f_flags & O_LARGEFILE))) {
+ if (pos >= MAX_NON_LFS)
+ return -EFBIG;
+ iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
+ }
+
+ /*
+ * Are we about to exceed the fs block limit ?
+ *
+ * If we have written data it becomes a short write. If we have
+ * exceeded without writing data we send a signal and return EFBIG.
+ * Linus frestrict idea will clean these up nicely..
+ */
+ if (unlikely(pos >= inode->i_sb->s_maxbytes))
+ return -EFBIG;
+
+ iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
+ return iov_iter_count(from);
+}
+EXPORT_SYMBOL(generic_write_checks);
+
+int pagecache_write_begin(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned flags,
+ struct page **pagep, void **fsdata)
+{
+ const struct address_space_operations *aops = mapping->a_ops;
+
+ return aops->write_begin(file, mapping, pos, len, flags,
+ pagep, fsdata);
+}
+EXPORT_SYMBOL(pagecache_write_begin);
+
+int pagecache_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ const struct address_space_operations *aops = mapping->a_ops;
+
+ return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
+}
+EXPORT_SYMBOL(pagecache_write_end);
+
+ssize_t
+generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ loff_t pos = iocb->ki_pos;
+ ssize_t written;
+ size_t write_len;
+ pgoff_t end;
+
+ write_len = iov_iter_count(from);
+ end = (pos + write_len - 1) >> PAGE_SHIFT;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ /* If there are pages to writeback, return */
+ if (filemap_range_has_page(inode->i_mapping, pos,
+ pos + iov_iter_count(from)))
+ return -EAGAIN;
+ } else {
+ written = filemap_write_and_wait_range(mapping, pos,
+ pos + write_len - 1);
+ if (written)
+ goto out;
+ }
+
+ /*
+ * After a write we want buffered reads to be sure to go to disk to get
+ * the new data. We invalidate clean cached page from the region we're
+ * about to write. We do this *before* the write so that we can return
+ * without clobbering -EIOCBQUEUED from ->direct_IO().
+ */
+ written = invalidate_inode_pages2_range(mapping,
+ pos >> PAGE_SHIFT, end);
+ /*
+ * If a page can not be invalidated, return 0 to fall back
+ * to buffered write.
+ */
+ if (written) {
+ if (written == -EBUSY)
+ return 0;
+ goto out;
+ }
+
+ written = mapping->a_ops->direct_IO(iocb, from);
+
+ /*
+ * Finally, try again to invalidate clean pages which might have been
+ * cached by non-direct readahead, or faulted in by get_user_pages()
+ * if the source of the write was an mmap'ed region of the file
+ * we're writing. Either one is a pretty crazy thing to do,
+ * so we don't support it 100%. If this invalidation
+ * fails, tough, the write still worked...
+ *
+ * Most of the time we do not need this since dio_complete() will do
+ * the invalidation for us. However there are some file systems that
+ * do not end up with dio_complete() being called, so let's not break
+ * them by removing it completely
+ */
+ if (mapping->nrpages)
+ invalidate_inode_pages2_range(mapping,
+ pos >> PAGE_SHIFT, end);
+
+ if (written > 0) {
+ pos += written;
+ write_len -= written;
+ if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
+ i_size_write(inode, pos);
+ mark_inode_dirty(inode);
+ }
+ iocb->ki_pos = pos;
+ }
+ iov_iter_revert(from, write_len - iov_iter_count(from));
+out:
+ return written;
+}
+EXPORT_SYMBOL(generic_file_direct_write);
+
+/*
+ * Find or create a page at the given pagecache position. Return the locked
+ * page. This function is specifically for buffered writes.
+ */
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags)
+{
+ struct page *page;
+ int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
+
+ if (flags & AOP_FLAG_NOFS)
+ fgp_flags |= FGP_NOFS;
+
+ page = pagecache_get_page(mapping, index, fgp_flags,
+ mapping_gfp_mask(mapping));
+ if (page)
+ wait_for_stable_page(page);
+
+ return page;
+}
+EXPORT_SYMBOL(grab_cache_page_write_begin);
+
+ssize_t generic_perform_write(struct file *file,
+ struct iov_iter *i, loff_t pos)
+{
+ struct address_space *mapping = file->f_mapping;
+ const struct address_space_operations *a_ops = mapping->a_ops;
+ long status = 0;
+ ssize_t written = 0;
+ unsigned int flags = 0;
+
+ do {
+ struct page *page;
+ unsigned long offset; /* Offset into pagecache page */
+ unsigned long bytes; /* Bytes to write to page */
+ size_t copied; /* Bytes copied from user */
+ void *fsdata;
+
+ offset = (pos & (PAGE_SIZE - 1));
+ bytes = min_t(unsigned long, PAGE_SIZE - offset,
+ iov_iter_count(i));
+
+again:
+ /*
+ * Bring in the user page that we will copy from _first_.
+ * Otherwise there's a nasty deadlock on copying from the
+ * same page as we're writing to, without it being marked
+ * up-to-date.
+ *
+ * Not only is this an optimisation, but it is also required
+ * to check that the address is actually valid, when atomic
+ * usercopies are used, below.
+ */
+ if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
+ status = -EFAULT;
+ break;
+ }
+
+ if (fatal_signal_pending(current)) {
+ status = -EINTR;
+ break;
+ }
+
+ status = a_ops->write_begin(file, mapping, pos, bytes, flags,
+ &page, &fsdata);
+ if (unlikely(status < 0))
+ break;
+
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_page(page);
+
+ copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
+ flush_dcache_page(page);
+
+ status = a_ops->write_end(file, mapping, pos, bytes, copied,
+ page, fsdata);
+ if (unlikely(status < 0))
+ break;
+ copied = status;
+
+ cond_resched();
+
+ iov_iter_advance(i, copied);
+ if (unlikely(copied == 0)) {
+ /*
+ * If we were unable to copy any data at all, we must
+ * fall back to a single segment length write.
+ *
+ * If we didn't fallback here, we could livelock
+ * because not all segments in the iov can be copied at
+ * once without a pagefault.
+ */
+ bytes = min_t(unsigned long, PAGE_SIZE - offset,
+ iov_iter_single_seg_count(i));
+ goto again;
+ }
+ pos += copied;
+ written += copied;
+
+ balance_dirty_pages_ratelimited(mapping);
+ } while (iov_iter_count(i));
+
+ return written ? written : status;
+}
+EXPORT_SYMBOL(generic_perform_write);
+
+/**
+ * __generic_file_write_iter - write data to a file
+ * @iocb: IO state structure (file, offset, etc.)
+ * @from: iov_iter with data to write
+ *
+ * This function does all the work needed for actually writing data to a
+ * file. It does all basic checks, removes SUID from the file, updates
+ * modification times and calls proper subroutines depending on whether we
+ * do direct IO or a standard buffered write.
+ *
+ * It expects i_mutex to be grabbed unless we work on a block device or similar
+ * object which does not need locking at all.
+ *
+ * This function does *not* take care of syncing data in case of O_SYNC write.
+ * A caller has to handle it. This is mainly due to the fact that we want to
+ * avoid syncing under i_mutex.
+ */
+ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space * mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ ssize_t written = 0;
+ ssize_t err;
+ ssize_t status;
+
+ /* We can write back this queue in page reclaim */
+ current->backing_dev_info = inode_to_bdi(inode);
+ err = file_remove_privs(file);
+ if (err)
+ goto out;
+
+ err = file_update_time(file);
+ if (err)
+ goto out;
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ loff_t pos, endbyte;
+
+ written = generic_file_direct_write(iocb, from);
+ /*
+ * If the write stopped short of completing, fall back to
+ * buffered writes. Some filesystems do this for writes to
+ * holes, for example. For DAX files, a buffered write will
+ * not succeed (even if it did, DAX does not handle dirty
+ * page-cache pages correctly).
+ */
+ if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
+ goto out;
+
+ status = generic_perform_write(file, from, pos = iocb->ki_pos);
+ /*
+ * If generic_perform_write() returned a synchronous error
+ * then we want to return the number of bytes which were
+ * direct-written, or the error code if that was zero. Note
+ * that this differs from normal direct-io semantics, which
+ * will return -EFOO even if some bytes were written.
+ */
+ if (unlikely(status < 0)) {
+ err = status;
+ goto out;
+ }
+ /*
+ * We need to ensure that the page cache pages are written to
+ * disk and invalidated to preserve the expected O_DIRECT
+ * semantics.
+ */
+ endbyte = pos + status - 1;
+ err = filemap_write_and_wait_range(mapping, pos, endbyte);
+ if (err == 0) {
+ iocb->ki_pos = endbyte + 1;
+ written += status;
+ invalidate_mapping_pages(mapping,
+ pos >> PAGE_SHIFT,
+ endbyte >> PAGE_SHIFT);
+ } else {
+ /*
+ * We don't know how much we wrote, so just return
+ * the number of bytes which were direct-written
+ */
+ }
+ } else {
+ written = generic_perform_write(file, from, iocb->ki_pos);
+ if (likely(written > 0))
+ iocb->ki_pos += written;
+ }
+out:
+ current->backing_dev_info = NULL;
+ return written ? written : err;
+}
+EXPORT_SYMBOL(__generic_file_write_iter);
+
+/**
+ * generic_file_write_iter - write data to a file
+ * @iocb: IO state structure
+ * @from: iov_iter with data to write
+ *
+ * This is a wrapper around __generic_file_write_iter() to be used by most
+ * filesystems. It takes care of syncing the file in case of O_SYNC file
+ * and acquires i_mutex as needed.
+ */
+ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ ssize_t ret;
+
+ inode_lock(inode);
+ ret = generic_write_checks(iocb, from);
+ if (ret > 0)
+ ret = __generic_file_write_iter(iocb, from);
+ inode_unlock(inode);
+
+ if (ret > 0)
+ ret = generic_write_sync(iocb, ret);
+ return ret;
+}
+EXPORT_SYMBOL(generic_file_write_iter);
+
+/**
+ * try_to_release_page() - release old fs-specific metadata on a page
+ *
+ * @page: the page which the kernel is trying to free
+ * @gfp_mask: memory allocation flags (and I/O mode)
+ *
+ * The address_space is to try to release any data against the page
+ * (presumably at page->private). If the release was successful, return '1'.
+ * Otherwise return zero.
+ *
+ * This may also be called if PG_fscache is set on a page, indicating that the
+ * page is known to the local caching routines.
+ *
+ * The @gfp_mask argument specifies whether I/O may be performed to release
+ * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
+ *
+ */
+int try_to_release_page(struct page *page, gfp_t gfp_mask)
+{
+ struct address_space * const mapping = page->mapping;
+
+ BUG_ON(!PageLocked(page));
+ if (PageWriteback(page))
+ return 0;
+
+ if (mapping && mapping->a_ops->releasepage)
+ return mapping->a_ops->releasepage(page, gfp_mask);
+ return try_to_free_buffers(page);
+}
+
+EXPORT_SYMBOL(try_to_release_page);