From c5a289f2ba1dae3ecd8bfd3ceeafe22e314a790a Mon Sep 17 00:00:00 2001 From: Guixin Liu Date: Wed, 17 Aug 2022 21:51:57 +0800 Subject: [PATCH] mm/filemap.c: fix the timing of asignment of prev_pos 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. 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. Link: https://lkml.kernel.org/r/1660744317-8183-1-git-send-email-kanie@linux.alibaba.com Fixes: 06c0444290cec ("mm/filemap.c: generic_file_buffered_read() now uses find_get_pages_contig") Signed-off-by: Guixin Liu Cc: Matthew Wilcox Cc: Kent Overstreet Signed-off-by: Andrew Morton --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 15800334147b..93fe744c9c57 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2711,8 +2711,8 @@ 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; -- 2.50.1