From 7c877586da3178974a8a94577b6045a48377ff25 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 25 Jun 2024 12:18:53 +0200 Subject: [PATCH] readahead: properly shorten readahead when falling back to do_page_cache_ra() When we succeed in creating some folios in page_cache_ra_order() but then need to fallback to single page folios, we don't shorten the amount to read passed to do_page_cache_ra() by the amount we've already read. This then results in reading more and also in placing another readahead mark in the middle of the readahead window which confuses readahead code. Fix the problem by properly reducing number of pages to read. Link: https://lkml.kernel.org/r/20240625101909.12234-3-jack@suse.cz Signed-off-by: Jan Kara Reviewed-by: Josef Bacik Tested-by: Zhang Peng Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/readahead.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index af0fbd302a38..1c58e0463be1 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -491,7 +491,8 @@ void page_cache_ra_order(struct readahead_control *ractl, struct file_ra_state *ra, unsigned int new_order) { struct address_space *mapping = ractl->mapping; - pgoff_t index = readahead_index(ractl); + pgoff_t start = readahead_index(ractl); + pgoff_t index = start; pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; pgoff_t mark = index + ra->size - ra->async_size; unsigned int nofs; @@ -544,7 +545,7 @@ void page_cache_ra_order(struct readahead_control *ractl, if (!err) return; fallback: - do_page_cache_ra(ractl, ra->size, ra->async_size); + do_page_cache_ra(ractl, ra->size - (index - start), ra->async_size); } /*