v4.19.13 snapshot.
diff --git a/mm/madvise.c b/mm/madvise.c
new file mode 100644
index 0000000..71d21df
--- /dev/null
+++ b/mm/madvise.c
@@ -0,0 +1,895 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/mm/madvise.c
+ *
+ * Copyright (C) 1999 Linus Torvalds
+ * Copyright (C) 2002 Christoph Hellwig
+ */
+
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/syscalls.h>
+#include <linux/mempolicy.h>
+#include <linux/page-isolation.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/hugetlb.h>
+#include <linux/falloc.h>
+#include <linux/sched.h>
+#include <linux/ksm.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/shmem_fs.h>
+#include <linux/mmu_notifier.h>
+
+#include <asm/tlb.h>
+
+#include "internal.h"
+
+/*
+ * Any behaviour which results in changes to the vma->vm_flags needs to
+ * take mmap_sem for writing. Others, which simply traverse vmas, need
+ * to only take it for reading.
+ */
+static int madvise_need_mmap_write(int behavior)
+{
+ switch (behavior) {
+ case MADV_REMOVE:
+ case MADV_WILLNEED:
+ case MADV_DONTNEED:
+ case MADV_FREE:
+ return 0;
+ default:
+ /* be safe, default to 1. list exceptions explicitly */
+ return 1;
+ }
+}
+
+/*
+ * We can potentially split a vm area into separate
+ * areas, each area with its own behavior.
+ */
+static long madvise_behavior(struct vm_area_struct *vma,
+ struct vm_area_struct **prev,
+ unsigned long start, unsigned long end, int behavior)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ int error = 0;
+ pgoff_t pgoff;
+ unsigned long new_flags = vma->vm_flags;
+
+ switch (behavior) {
+ case MADV_NORMAL:
+ new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
+ break;
+ case MADV_SEQUENTIAL:
+ new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
+ break;
+ case MADV_RANDOM:
+ new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
+ break;
+ case MADV_DONTFORK:
+ new_flags |= VM_DONTCOPY;
+ break;
+ case MADV_DOFORK:
+ if (vma->vm_flags & VM_IO) {
+ error = -EINVAL;
+ goto out;
+ }
+ new_flags &= ~VM_DONTCOPY;
+ break;
+ case MADV_WIPEONFORK:
+ /* MADV_WIPEONFORK is only supported on anonymous memory. */
+ if (vma->vm_file || vma->vm_flags & VM_SHARED) {
+ error = -EINVAL;
+ goto out;
+ }
+ new_flags |= VM_WIPEONFORK;
+ break;
+ case MADV_KEEPONFORK:
+ new_flags &= ~VM_WIPEONFORK;
+ break;
+ case MADV_DONTDUMP:
+ new_flags |= VM_DONTDUMP;
+ break;
+ case MADV_DODUMP:
+ if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) {
+ error = -EINVAL;
+ goto out;
+ }
+ new_flags &= ~VM_DONTDUMP;
+ break;
+ case MADV_MERGEABLE:
+ case MADV_UNMERGEABLE:
+ error = ksm_madvise(vma, start, end, behavior, &new_flags);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
+ goto out;
+ }
+ break;
+ case MADV_HUGEPAGE:
+ case MADV_NOHUGEPAGE:
+ error = hugepage_madvise(vma, &new_flags, behavior);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
+ goto out;
+ }
+ break;
+ }
+
+ if (new_flags == vma->vm_flags) {
+ *prev = vma;
+ goto out;
+ }
+
+ pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
+ *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
+ vma->vm_file, pgoff, vma_policy(vma),
+ vma->vm_userfaultfd_ctx);
+ if (*prev) {
+ vma = *prev;
+ goto success;
+ }
+
+ *prev = vma;
+
+ if (start != vma->vm_start) {
+ if (unlikely(mm->map_count >= sysctl_max_map_count)) {
+ error = -ENOMEM;
+ goto out;
+ }
+ error = __split_vma(mm, vma, start, 1);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
+ goto out;
+ }
+ }
+
+ if (end != vma->vm_end) {
+ if (unlikely(mm->map_count >= sysctl_max_map_count)) {
+ error = -ENOMEM;
+ goto out;
+ }
+ error = __split_vma(mm, vma, end, 0);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
+ goto out;
+ }
+ }
+
+success:
+ /*
+ * vm_flags is protected by the mmap_sem held in write mode.
+ */
+ vma->vm_flags = new_flags;
+out:
+ return error;
+}
+
+#ifdef CONFIG_SWAP
+static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
+ unsigned long end, struct mm_walk *walk)
+{
+ pte_t *orig_pte;
+ struct vm_area_struct *vma = walk->private;
+ unsigned long index;
+
+ if (pmd_none_or_trans_huge_or_clear_bad(pmd))
+ return 0;
+
+ for (index = start; index != end; index += PAGE_SIZE) {
+ pte_t pte;
+ swp_entry_t entry;
+ struct page *page;
+ spinlock_t *ptl;
+
+ orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
+ pte = *(orig_pte + ((index - start) / PAGE_SIZE));
+ pte_unmap_unlock(orig_pte, ptl);
+
+ if (pte_present(pte) || pte_none(pte))
+ continue;
+ entry = pte_to_swp_entry(pte);
+ if (unlikely(non_swap_entry(entry)))
+ continue;
+
+ page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
+ vma, index, false);
+ if (page)
+ put_page(page);
+ }
+
+ return 0;
+}
+
+static void force_swapin_readahead(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ struct mm_walk walk = {
+ .mm = vma->vm_mm,
+ .pmd_entry = swapin_walk_pmd_entry,
+ .private = vma,
+ };
+
+ walk_page_range(start, end, &walk);
+
+ lru_add_drain(); /* Push any new pages onto the LRU now */
+}
+
+static void force_shm_swapin_readahead(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct address_space *mapping)
+{
+ pgoff_t index;
+ struct page *page;
+ swp_entry_t swap;
+
+ for (; start < end; start += PAGE_SIZE) {
+ index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+
+ page = find_get_entry(mapping, index);
+ if (!radix_tree_exceptional_entry(page)) {
+ if (page)
+ put_page(page);
+ continue;
+ }
+ swap = radix_to_swp_entry(page);
+ page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
+ NULL, 0, false);
+ if (page)
+ put_page(page);
+ }
+
+ lru_add_drain(); /* Push any new pages onto the LRU now */
+}
+#endif /* CONFIG_SWAP */
+
+/*
+ * Schedule all required I/O operations. Do not wait for completion.
+ */
+static long madvise_willneed(struct vm_area_struct *vma,
+ struct vm_area_struct **prev,
+ unsigned long start, unsigned long end)
+{
+ struct file *file = vma->vm_file;
+
+ *prev = vma;
+#ifdef CONFIG_SWAP
+ if (!file) {
+ force_swapin_readahead(vma, start, end);
+ return 0;
+ }
+
+ if (shmem_mapping(file->f_mapping)) {
+ force_shm_swapin_readahead(vma, start, end,
+ file->f_mapping);
+ return 0;
+ }
+#else
+ if (!file)
+ return -EBADF;
+#endif
+
+ if (IS_DAX(file_inode(file))) {
+ /* no bad return value, but ignore advice */
+ return 0;
+ }
+
+ start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+ if (end > vma->vm_end)
+ end = vma->vm_end;
+ end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+
+ force_page_cache_readahead(file->f_mapping, file, start, end - start);
+ return 0;
+}
+
+static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
+
+{
+ struct mmu_gather *tlb = walk->private;
+ struct mm_struct *mm = tlb->mm;
+ struct vm_area_struct *vma = walk->vma;
+ spinlock_t *ptl;
+ pte_t *orig_pte, *pte, ptent;
+ struct page *page;
+ int nr_swap = 0;
+ unsigned long next;
+
+ next = pmd_addr_end(addr, end);
+ if (pmd_trans_huge(*pmd))
+ if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
+ goto next;
+
+ if (pmd_trans_unstable(pmd))
+ return 0;
+
+ tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
+ orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ flush_tlb_batched_pending(mm);
+ arch_enter_lazy_mmu_mode();
+ for (; addr != end; pte++, addr += PAGE_SIZE) {
+ ptent = *pte;
+
+ if (pte_none(ptent))
+ continue;
+ /*
+ * If the pte has swp_entry, just clear page table to
+ * prevent swap-in which is more expensive rather than
+ * (page allocation + zeroing).
+ */
+ if (!pte_present(ptent)) {
+ swp_entry_t entry;
+
+ entry = pte_to_swp_entry(ptent);
+ if (non_swap_entry(entry))
+ continue;
+ nr_swap--;
+ free_swap_and_cache(entry);
+ pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
+ continue;
+ }
+
+ page = _vm_normal_page(vma, addr, ptent, true);
+ if (!page)
+ continue;
+
+ /*
+ * If pmd isn't transhuge but the page is THP and
+ * is owned by only this process, split it and
+ * deactivate all pages.
+ */
+ if (PageTransCompound(page)) {
+ if (page_mapcount(page) != 1)
+ goto out;
+ get_page(page);
+ if (!trylock_page(page)) {
+ put_page(page);
+ goto out;
+ }
+ pte_unmap_unlock(orig_pte, ptl);
+ if (split_huge_page(page)) {
+ unlock_page(page);
+ put_page(page);
+ pte_offset_map_lock(mm, pmd, addr, &ptl);
+ goto out;
+ }
+ unlock_page(page);
+ put_page(page);
+ pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ pte--;
+ addr -= PAGE_SIZE;
+ continue;
+ }
+
+ VM_BUG_ON_PAGE(PageTransCompound(page), page);
+
+ if (PageSwapCache(page) || PageDirty(page)) {
+ if (!trylock_page(page))
+ continue;
+ /*
+ * If page is shared with others, we couldn't clear
+ * PG_dirty of the page.
+ */
+ if (page_mapcount(page) != 1) {
+ unlock_page(page);
+ continue;
+ }
+
+ if (PageSwapCache(page) && !try_to_free_swap(page)) {
+ unlock_page(page);
+ continue;
+ }
+
+ ClearPageDirty(page);
+ unlock_page(page);
+ }
+
+ if (pte_young(ptent) || pte_dirty(ptent)) {
+ /*
+ * Some of architecture(ex, PPC) don't update TLB
+ * with set_pte_at and tlb_remove_tlb_entry so for
+ * the portability, remap the pte with old|clean
+ * after pte clearing.
+ */
+ ptent = ptep_get_and_clear_full(mm, addr, pte,
+ tlb->fullmm);
+
+ ptent = pte_mkold(ptent);
+ ptent = pte_mkclean(ptent);
+ set_pte_at(mm, addr, pte, ptent);
+ tlb_remove_tlb_entry(tlb, pte, addr);
+ }
+ mark_page_lazyfree(page);
+ }
+out:
+ if (nr_swap) {
+ if (current->mm == mm)
+ sync_mm_rss(mm);
+
+ add_mm_counter(mm, MM_SWAPENTS, nr_swap);
+ }
+ arch_leave_lazy_mmu_mode();
+ pte_unmap_unlock(orig_pte, ptl);
+ cond_resched();
+next:
+ return 0;
+}
+
+static void madvise_free_page_range(struct mmu_gather *tlb,
+ struct vm_area_struct *vma,
+ unsigned long addr, unsigned long end)
+{
+ struct mm_walk free_walk = {
+ .pmd_entry = madvise_free_pte_range,
+ .mm = vma->vm_mm,
+ .private = tlb,
+ };
+
+ tlb_start_vma(tlb, vma);
+ walk_page_range(addr, end, &free_walk);
+ tlb_end_vma(tlb, vma);
+}
+
+static int madvise_free_single_vma(struct vm_area_struct *vma,
+ unsigned long start_addr, unsigned long end_addr)
+{
+ unsigned long start, end;
+ struct mm_struct *mm = vma->vm_mm;
+ struct mmu_gather tlb;
+
+ /* MADV_FREE works for only anon vma at the moment */
+ if (!vma_is_anonymous(vma))
+ return -EINVAL;
+
+ start = max(vma->vm_start, start_addr);
+ if (start >= vma->vm_end)
+ return -EINVAL;
+ end = min(vma->vm_end, end_addr);
+ if (end <= vma->vm_start)
+ return -EINVAL;
+
+ lru_add_drain();
+ tlb_gather_mmu(&tlb, mm, start, end);
+ update_hiwater_rss(mm);
+
+ mmu_notifier_invalidate_range_start(mm, start, end);
+ madvise_free_page_range(&tlb, vma, start, end);
+ mmu_notifier_invalidate_range_end(mm, start, end);
+ tlb_finish_mmu(&tlb, start, end);
+
+ return 0;
+}
+
+/*
+ * Application no longer needs these pages. If the pages are dirty,
+ * it's OK to just throw them away. The app will be more careful about
+ * data it wants to keep. Be sure to free swap resources too. The
+ * zap_page_range call sets things up for shrink_active_list to actually free
+ * these pages later if no one else has touched them in the meantime,
+ * although we could add these pages to a global reuse list for
+ * shrink_active_list to pick up before reclaiming other pages.
+ *
+ * NB: This interface discards data rather than pushes it out to swap,
+ * as some implementations do. This has performance implications for
+ * applications like large transactional databases which want to discard
+ * pages in anonymous maps after committing to backing store the data
+ * that was kept in them. There is no reason to write this data out to
+ * the swap area if the application is discarding it.
+ *
+ * An interface that causes the system to free clean pages and flush
+ * dirty pages is already available as msync(MS_INVALIDATE).
+ */
+static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ zap_page_range(vma, start, end - start);
+ return 0;
+}
+
+static long madvise_dontneed_free(struct vm_area_struct *vma,
+ struct vm_area_struct **prev,
+ unsigned long start, unsigned long end,
+ int behavior)
+{
+ *prev = vma;
+ if (!can_madv_dontneed_vma(vma))
+ return -EINVAL;
+
+ if (!userfaultfd_remove(vma, start, end)) {
+ *prev = NULL; /* mmap_sem has been dropped, prev is stale */
+
+ down_read(¤t->mm->mmap_sem);
+ vma = find_vma(current->mm, start);
+ if (!vma)
+ return -ENOMEM;
+ if (start < vma->vm_start) {
+ /*
+ * This "vma" under revalidation is the one
+ * with the lowest vma->vm_start where start
+ * is also < vma->vm_end. If start <
+ * vma->vm_start it means an hole materialized
+ * in the user address space within the
+ * virtual range passed to MADV_DONTNEED
+ * or MADV_FREE.
+ */
+ return -ENOMEM;
+ }
+ if (!can_madv_dontneed_vma(vma))
+ return -EINVAL;
+ if (end > vma->vm_end) {
+ /*
+ * Don't fail if end > vma->vm_end. If the old
+ * vma was splitted while the mmap_sem was
+ * released the effect of the concurrent
+ * operation may not cause madvise() to
+ * have an undefined result. There may be an
+ * adjacent next vma that we'll walk
+ * next. userfaultfd_remove() will generate an
+ * UFFD_EVENT_REMOVE repetition on the
+ * end-vma->vm_end range, but the manager can
+ * handle a repetition fine.
+ */
+ end = vma->vm_end;
+ }
+ VM_WARN_ON(start >= end);
+ }
+
+ if (behavior == MADV_DONTNEED)
+ return madvise_dontneed_single_vma(vma, start, end);
+ else if (behavior == MADV_FREE)
+ return madvise_free_single_vma(vma, start, end);
+ else
+ return -EINVAL;
+}
+
+/*
+ * Application wants to free up the pages and associated backing store.
+ * This is effectively punching a hole into the middle of a file.
+ */
+static long madvise_remove(struct vm_area_struct *vma,
+ struct vm_area_struct **prev,
+ unsigned long start, unsigned long end)
+{
+ loff_t offset;
+ int error;
+ struct file *f;
+
+ *prev = NULL; /* tell sys_madvise we drop mmap_sem */
+
+ if (vma->vm_flags & VM_LOCKED)
+ return -EINVAL;
+
+ f = vma->vm_file;
+
+ if (!f || !f->f_mapping || !f->f_mapping->host) {
+ return -EINVAL;
+ }
+
+ if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
+ return -EACCES;
+
+ offset = (loff_t)(start - vma->vm_start)
+ + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+
+ /*
+ * Filesystem's fallocate may need to take i_mutex. We need to
+ * explicitly grab a reference because the vma (and hence the
+ * vma's reference to the file) can go away as soon as we drop
+ * mmap_sem.
+ */
+ get_file(f);
+ if (userfaultfd_remove(vma, start, end)) {
+ /* mmap_sem was not released by userfaultfd_remove() */
+ up_read(¤t->mm->mmap_sem);
+ }
+ error = vfs_fallocate(f,
+ FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+ offset, end - start);
+ fput(f);
+ down_read(¤t->mm->mmap_sem);
+ return error;
+}
+
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Error injection support for memory error handling.
+ */
+static int madvise_inject_error(int behavior,
+ unsigned long start, unsigned long end)
+{
+ struct page *page;
+ struct zone *zone;
+ unsigned int order;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+
+ for (; start < end; start += PAGE_SIZE << order) {
+ unsigned long pfn;
+ int ret;
+
+ ret = get_user_pages_fast(start, 1, 0, &page);
+ if (ret != 1)
+ return ret;
+ pfn = page_to_pfn(page);
+
+ /*
+ * When soft offlining hugepages, after migrating the page
+ * we dissolve it, therefore in the second loop "page" will
+ * no longer be a compound page, and order will be 0.
+ */
+ order = compound_order(compound_head(page));
+
+ if (PageHWPoison(page)) {
+ put_page(page);
+ continue;
+ }
+
+ if (behavior == MADV_SOFT_OFFLINE) {
+ pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
+ pfn, start);
+
+ ret = soft_offline_page(page, MF_COUNT_INCREASED);
+ if (ret)
+ return ret;
+ continue;
+ }
+
+ pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
+ pfn, start);
+
+ /*
+ * Drop the page reference taken by get_user_pages_fast(). In
+ * the absence of MF_COUNT_INCREASED the memory_failure()
+ * routine is responsible for pinning the page to prevent it
+ * from being released back to the page allocator.
+ */
+ put_page(page);
+ ret = memory_failure(pfn, 0);
+ if (ret)
+ return ret;
+ }
+
+ /* Ensure that all poisoned pages are removed from per-cpu lists */
+ for_each_populated_zone(zone)
+ drain_all_pages(zone);
+
+ return 0;
+}
+#endif
+
+static long
+madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
+ unsigned long start, unsigned long end, int behavior)
+{
+ switch (behavior) {
+ case MADV_REMOVE:
+ return madvise_remove(vma, prev, start, end);
+ case MADV_WILLNEED:
+ return madvise_willneed(vma, prev, start, end);
+ case MADV_FREE:
+ case MADV_DONTNEED:
+ return madvise_dontneed_free(vma, prev, start, end, behavior);
+ default:
+ return madvise_behavior(vma, prev, start, end, behavior);
+ }
+}
+
+static bool
+madvise_behavior_valid(int behavior)
+{
+ switch (behavior) {
+ case MADV_DOFORK:
+ case MADV_DONTFORK:
+ case MADV_NORMAL:
+ case MADV_SEQUENTIAL:
+ case MADV_RANDOM:
+ case MADV_REMOVE:
+ case MADV_WILLNEED:
+ case MADV_DONTNEED:
+ case MADV_FREE:
+#ifdef CONFIG_KSM
+ case MADV_MERGEABLE:
+ case MADV_UNMERGEABLE:
+#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ case MADV_HUGEPAGE:
+ case MADV_NOHUGEPAGE:
+#endif
+ case MADV_DONTDUMP:
+ case MADV_DODUMP:
+ case MADV_WIPEONFORK:
+ case MADV_KEEPONFORK:
+#ifdef CONFIG_MEMORY_FAILURE
+ case MADV_SOFT_OFFLINE:
+ case MADV_HWPOISON:
+#endif
+ return true;
+
+ default:
+ return false;
+ }
+}
+
+/*
+ * The madvise(2) system call.
+ *
+ * Applications can use madvise() to advise the kernel how it should
+ * handle paging I/O in this VM area. The idea is to help the kernel
+ * use appropriate read-ahead and caching techniques. The information
+ * provided is advisory only, and can be safely disregarded by the
+ * kernel without affecting the correct operation of the application.
+ *
+ * behavior values:
+ * MADV_NORMAL - the default behavior is to read clusters. This
+ * results in some read-ahead and read-behind.
+ * MADV_RANDOM - the system should read the minimum amount of data
+ * on any access, since it is unlikely that the appli-
+ * cation will need more than what it asks for.
+ * MADV_SEQUENTIAL - pages in the given range will probably be accessed
+ * once, so they can be aggressively read ahead, and
+ * can be freed soon after they are accessed.
+ * MADV_WILLNEED - the application is notifying the system to read
+ * some pages ahead.
+ * MADV_DONTNEED - the application is finished with the given range,
+ * so the kernel can free resources associated with it.
+ * MADV_FREE - the application marks pages in the given range as lazy free,
+ * where actual purges are postponed until memory pressure happens.
+ * MADV_REMOVE - the application wants to free up the given range of
+ * pages and associated backing store.
+ * MADV_DONTFORK - omit this area from child's address space when forking:
+ * typically, to avoid COWing pages pinned by get_user_pages().
+ * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
+ * MADV_WIPEONFORK - present the child process with zero-filled memory in this
+ * range after a fork.
+ * MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
+ * MADV_HWPOISON - trigger memory error handler as if the given memory range
+ * were corrupted by unrecoverable hardware memory failure.
+ * MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
+ * MADV_MERGEABLE - the application recommends that KSM try to merge pages in
+ * this area with pages of identical content from other such areas.
+ * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
+ * MADV_HUGEPAGE - the application wants to back the given range by transparent
+ * huge pages in the future. Existing pages might be coalesced and
+ * new pages might be allocated as THP.
+ * MADV_NOHUGEPAGE - mark the given range as not worth being backed by
+ * transparent huge pages so the existing pages will not be
+ * coalesced into THP and new pages will not be allocated as THP.
+ * MADV_DONTDUMP - the application wants to prevent pages in the given range
+ * from being included in its core dump.
+ * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
+ *
+ * return values:
+ * zero - success
+ * -EINVAL - start + len < 0, start is not page-aligned,
+ * "behavior" is not a valid value, or application
+ * is attempting to release locked or shared pages,
+ * or the specified address range includes file, Huge TLB,
+ * MAP_SHARED or VMPFNMAP range.
+ * -ENOMEM - addresses in the specified range are not currently
+ * mapped, or are outside the AS of the process.
+ * -EIO - an I/O error occurred while paging in data.
+ * -EBADF - map exists, but area maps something that isn't a file.
+ * -EAGAIN - a kernel resource was temporarily unavailable.
+ */
+SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
+{
+ unsigned long end, tmp;
+ struct vm_area_struct *vma, *prev;
+ int unmapped_error = 0;
+ int error = -EINVAL;
+ int write;
+ size_t len;
+ struct blk_plug plug;
+
+ if (!madvise_behavior_valid(behavior))
+ return error;
+
+ if (start & ~PAGE_MASK)
+ return error;
+ len = (len_in + ~PAGE_MASK) & PAGE_MASK;
+
+ /* Check to see whether len was rounded up from small -ve to zero */
+ if (len_in && !len)
+ return error;
+
+ end = start + len;
+ if (end < start)
+ return error;
+
+ error = 0;
+ if (end == start)
+ return error;
+
+#ifdef CONFIG_MEMORY_FAILURE
+ if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
+ return madvise_inject_error(behavior, start, start + len_in);
+#endif
+
+ write = madvise_need_mmap_write(behavior);
+ if (write) {
+ if (down_write_killable(¤t->mm->mmap_sem))
+ return -EINTR;
+ } else {
+ down_read(¤t->mm->mmap_sem);
+ }
+
+ /*
+ * If the interval [start,end) covers some unmapped address
+ * ranges, just ignore them, but return -ENOMEM at the end.
+ * - different from the way of handling in mlock etc.
+ */
+ vma = find_vma_prev(current->mm, start, &prev);
+ if (vma && start > vma->vm_start)
+ prev = vma;
+
+ blk_start_plug(&plug);
+ for (;;) {
+ /* Still start < end. */
+ error = -ENOMEM;
+ if (!vma)
+ goto out;
+
+ /* Here start < (end|vma->vm_end). */
+ if (start < vma->vm_start) {
+ unmapped_error = -ENOMEM;
+ start = vma->vm_start;
+ if (start >= end)
+ goto out;
+ }
+
+ /* Here vma->vm_start <= start < (end|vma->vm_end) */
+ tmp = vma->vm_end;
+ if (end < tmp)
+ tmp = end;
+
+ /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
+ error = madvise_vma(vma, &prev, start, tmp, behavior);
+ if (error)
+ goto out;
+ start = tmp;
+ if (prev && start < prev->vm_end)
+ start = prev->vm_end;
+ error = unmapped_error;
+ if (start >= end)
+ goto out;
+ if (prev)
+ vma = prev->vm_next;
+ else /* madvise_remove dropped mmap_sem */
+ vma = find_vma(current->mm, start);
+ }
+out:
+ blk_finish_plug(&plug);
+ if (write)
+ up_write(¤t->mm->mmap_sem);
+ else
+ up_read(¤t->mm->mmap_sem);
+
+ return error;
+}