From: Jan Kara <jack@suse.cz> mainline inclusion from mainline-v6.14-rc1 commit 7a1eb89f79188ec32599064eca7c14d42260760a category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBRWBB Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Patch series "readahead: Reintroduce fix for improper RA window sizing". This small patch series reintroduces a fix of readahead window confusion (and thus read throughput reduction) when page_cache_ra_order() ends up failing due to folios already present in the page cache. After thinking about this for a while I have ended up with a dumb fix that just rechecks if we have something to read before calling do_page_cache_ra(). This fixes the problem reported in [1]. I still think it doesn't make much sense to update readahead window size in read_pages() so patch 1 removes that but the real fix in patch 2 does not depend on it. [1] https://lore.kernel.org/all/49648605-d800-4859-be49-624bbe60519d@gmail.com This patch (of 2): When ->readahead callback doesn't read all requested pages, read_pages() shortens the readahead window (ra->size). However we don't know why pages were not read and what appropriate window size is. So don't try to secondguess the filesystem. If it needs different readahead window, it should set it manually similarly as during expansion the filesystem can use readahead_expand(). Link: https://lkml.kernel.org/r/20241204181016.15273-1-jack@suse.cz Link: https://lkml.kernel.org/r/20241204181016.15273-2-jack@suse.cz Signed-off-by: Jan Kara <jack@suse.cz> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> --- mm/readahead.c | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 5aba3a9973..7d36a29e1d 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -164,20 +164,10 @@ static void read_pages(struct readahead_control *rac) if (aops->readahead) { aops->readahead(rac); - /* - * Clean up the remaining folios. The sizes in ->ra - * may be used to size the next readahead, so make sure - * they accurately reflect what happened. - */ + /* Clean up the remaining folios. */ while ((folio = readahead_folio(rac)) != NULL) { - unsigned long nr = folio_nr_pages(folio); - folio_get(folio); - rac->ra->size -= nr; - if (rac->ra->async_size >= nr) { - rac->ra->async_size -= nr; - filemap_remove_folio(folio); - } + filemap_remove_folio(folio); folio_unlock(folio); folio_put(folio); } -- 2.25.1