In f2fs_read_data_large_folio(), read_pages_pending is incremented only
after the subpage has been added to the BIO. With a heavily fragmented
file, each new subpage can force submission of the previous BIO.
If the BIO completes quickly, f2fs_finish_read_bio() may decrement
read_pages_pending to zero and call folio_end_read() while the read loop
is still processing other subpages of the same large folio.
Fix the ordering by incrementing read_pages_pending before any possible
BIO submission for the current subpage, matching the iomap ordering and
preventing premature folio_end_read().
Signed-off-by: Nanzhe Zhao <nzzhao@126.com>
---
fs/f2fs/data.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index ab091b294fa7..4bef04560924 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2486,6 +2486,18 @@ static int f2fs_read_data_large_folio(struct inode *inode,
continue;
}
+ /* We must increment read_pages_pending before possible BIOs submitting
+ * to prevent from premature folio_end_read() call on folio
+ */
+ if (folio_test_large(folio)) {
+ ffs = ffs_find_or_alloc(folio);
+
+ /* set the bitmap to wait */
+ spin_lock_irq(&ffs->state_lock);
+ ffs->read_pages_pending++;
+ spin_unlock_irq(&ffs->state_lock);
+ }
+
/*
* This page will go to BIO. Do we need to send this
* BIO off first?
@@ -2513,15 +2525,6 @@ static int f2fs_read_data_large_folio(struct inode *inode,
offset << PAGE_SHIFT))
goto submit_and_realloc;
- if (folio_test_large(folio)) {
- ffs = ffs_find_or_alloc(folio);
-
- /* set the bitmap to wait */
- spin_lock_irq(&ffs->state_lock);
- ffs->read_pages_pending++;
- spin_unlock_irq(&ffs->state_lock);
- }
-
inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
f2fs_update_iostat(F2FS_I_SB(inode), NULL, FS_DATA_READ_IO,
F2FS_BLKSIZE);
--
2.34.1