The prev_pos should be assigned before the iocb->ki_pos is incremented,
so that the prev_pos is the exact location of the last visit.
Fixes: 06c0444290cec ("mm/filemap.c: generic_file_buffered_read() now
uses find_get_pages_contig")
Signed-off-by: Guixin Liu <kanie@xxxxxxxxxxxxxxxxx>
---
Hi guys,
When I`m running repetitive 4k read io which has same offset,
I find that access to folio_mark_accessed is inevitable in the
read process, the reason is that the prev_pos is assigned after the
iocb->ki_pos is incremented, so that the prev_pos is always not equal
to the position currently visited.
Is this a bug that needs fixing?
mm/filemap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 660490c..68fd987 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2703,8 +2703,8 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
copied = copy_folio_to_iter(folio, offset, bytes, iter);
already_read += copied;
- iocb->ki_pos += copied;
ra->prev_pos = iocb->ki_pos;
+ iocb->ki_pos += copied;
if (copied < bytes) {
error = -EFAULT;
--
1.8.3.1
