v4.19.13 snapshot.
diff --git a/mm/fadvise.c b/mm/fadvise.c
new file mode 100644
index 0000000..467bcd0
--- /dev/null
+++ b/mm/fadvise.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mm/fadvise.c
+ *
+ * Copyright (C) 2002, Linus Torvalds
+ *
+ * 11Jan2003 Andrew Morton
+ * Initial version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+#include <linux/fadvise.h>
+#include <linux/writeback.h>
+#include <linux/syscalls.h>
+#include <linux/swap.h>
+
+#include <asm/unistd.h>
+
+/*
+ * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
+ * deactivate the pages and clear PG_Referenced.
+ */
+
+static int generic_fadvise(struct file *file, loff_t offset, loff_t len,
+ int advice)
+{
+ struct inode *inode;
+ struct address_space *mapping;
+ struct backing_dev_info *bdi;
+ loff_t endbyte; /* inclusive */
+ pgoff_t start_index;
+ pgoff_t end_index;
+ unsigned long nrpages;
+
+ inode = file_inode(file);
+ if (S_ISFIFO(inode->i_mode))
+ return -ESPIPE;
+
+ mapping = file->f_mapping;
+ if (!mapping || len < 0)
+ return -EINVAL;
+
+ bdi = inode_to_bdi(mapping->host);
+
+ if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
+ switch (advice) {
+ case POSIX_FADV_NORMAL:
+ case POSIX_FADV_RANDOM:
+ case POSIX_FADV_SEQUENTIAL:
+ case POSIX_FADV_WILLNEED:
+ case POSIX_FADV_NOREUSE:
+ case POSIX_FADV_DONTNEED:
+ /* no bad return value, but ignore advice */
+ break;
+ default:
+ return -EINVAL;
+ }
+ return 0;
+ }
+
+ /*
+ * Careful about overflows. Len == 0 means "as much as possible". Use
+ * unsigned math because signed overflows are undefined and UBSan
+ * complains.
+ */
+ endbyte = (u64)offset + (u64)len;
+ if (!len || endbyte < len)
+ endbyte = -1;
+ else
+ endbyte--; /* inclusive */
+
+ switch (advice) {
+ case POSIX_FADV_NORMAL:
+ file->f_ra.ra_pages = bdi->ra_pages;
+ spin_lock(&file->f_lock);
+ file->f_mode &= ~FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
+ break;
+ case POSIX_FADV_RANDOM:
+ spin_lock(&file->f_lock);
+ file->f_mode |= FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
+ break;
+ case POSIX_FADV_SEQUENTIAL:
+ file->f_ra.ra_pages = bdi->ra_pages * 2;
+ spin_lock(&file->f_lock);
+ file->f_mode &= ~FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
+ break;
+ case POSIX_FADV_WILLNEED:
+ /* First and last PARTIAL page! */
+ start_index = offset >> PAGE_SHIFT;
+ end_index = endbyte >> PAGE_SHIFT;
+
+ /* Careful about overflow on the "+1" */
+ nrpages = end_index - start_index + 1;
+ if (!nrpages)
+ nrpages = ~0UL;
+
+ /*
+ * Ignore return value because fadvise() shall return
+ * success even if filesystem can't retrieve a hint,
+ */
+ force_page_cache_readahead(mapping, file, start_index, nrpages);
+ break;
+ case POSIX_FADV_NOREUSE:
+ break;
+ case POSIX_FADV_DONTNEED:
+ if (!inode_write_congested(mapping->host))
+ __filemap_fdatawrite_range(mapping, offset, endbyte,
+ WB_SYNC_NONE);
+
+ /*
+ * First and last FULL page! Partial pages are deliberately
+ * preserved on the expectation that it is better to preserve
+ * needed memory than to discard unneeded memory.
+ */
+ start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
+ end_index = (endbyte >> PAGE_SHIFT);
+ /*
+ * The page at end_index will be inclusively discarded according
+ * by invalidate_mapping_pages(), so subtracting 1 from
+ * end_index means we will skip the last page. But if endbyte
+ * is page aligned or is at the end of file, we should not skip
+ * that page - discarding the last page is safe enough.
+ */
+ if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
+ endbyte != inode->i_size - 1) {
+ /* First page is tricky as 0 - 1 = -1, but pgoff_t
+ * is unsigned, so the end_index >= start_index
+ * check below would be true and we'll discard the whole
+ * file cache which is not what was asked.
+ */
+ if (end_index == 0)
+ break;
+
+ end_index--;
+ }
+
+ if (end_index >= start_index) {
+ unsigned long count;
+
+ /*
+ * It's common to FADV_DONTNEED right after
+ * the read or write that instantiates the
+ * pages, in which case there will be some
+ * sitting on the local LRU cache. Try to
+ * avoid the expensive remote drain and the
+ * second cache tree walk below by flushing
+ * them out right away.
+ */
+ lru_add_drain();
+
+ count = invalidate_mapping_pages(mapping,
+ start_index, end_index);
+
+ /*
+ * If fewer pages were invalidated than expected then
+ * it is possible that some of the pages were on
+ * a per-cpu pagevec for a remote CPU. Drain all
+ * pagevecs and try again.
+ */
+ if (count < (end_index - start_index + 1)) {
+ lru_add_drain_all();
+ invalidate_mapping_pages(mapping, start_index,
+ end_index);
+ }
+ }
+ break;
+ default:
+ return -EINVAL;
+ }
+ return 0;
+}
+
+int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+ if (file->f_op->fadvise)
+ return file->f_op->fadvise(file, offset, len, advice);
+
+ return generic_fadvise(file, offset, len, advice);
+}
+EXPORT_SYMBOL(vfs_fadvise);
+
+#ifdef CONFIG_ADVISE_SYSCALLS
+
+int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
+{
+ struct fd f = fdget(fd);
+ int ret;
+
+ if (!f.file)
+ return -EBADF;
+
+ ret = vfs_fadvise(f.file, offset, len, advice);
+
+ fdput(f);
+ return ret;
+}
+
+SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
+{
+ return ksys_fadvise64_64(fd, offset, len, advice);
+}
+
+#ifdef __ARCH_WANT_SYS_FADVISE64
+
+SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
+{
+ return ksys_fadvise64_64(fd, offset, len, advice);
+}
+
+#endif
+#endif