When reading the page from the disk, we can race with Direct I/O which can get
the page lock (before prepare_uptodate_page() gets it) and can go ahead and
invalidate the page. Hence if the page is not found in the inode's address
space, retry the operation of getting a page.
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
---
fs/btrfs/file.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 5715e29..76db77c 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1316,6 +1316,7 @@ static noinline int prepare_pages(struct inode *inode, struct page **pages,
int faili;
for (i = 0; i < num_pages; i++) {
+again:
pages[i] = find_or_create_page(inode->i_mapping, index + i,
mask | __GFP_WRITE);
if (!pages[i]) {
@@ -1330,6 +1331,21 @@ static noinline int prepare_pages(struct inode *inode, struct page **pages,
if (i == num_pages - 1)
err = prepare_uptodate_page(pages[i],
pos + write_bytes, false);
+
+ /*
+ * When reading the page from the disk, we can race
+ * with direct i/o which can get the page lock (before
+ * prepare_uptodate_page() gets it) and can go ahead
+ * and invalidate the page. Hence if the page is found
+ * to be not belonging to the inode's address space,
+ * retry the operation of getting a page.
+ */
+ if (unlikely(pages[i]->mapping != inode->i_mapping)) {
+ unlock_page(pages[i]);
+ page_cache_release(pages[i]);
+ goto again;
+ }
+
if (err) {
page_cache_release(pages[i]);
faili = i - 1;
--
2.1.0
--
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