The patch titled
Subject: readahead: properly shorten readahead when falling back to do_page_cache_ra()
has been added to the -mm mm-unstable branch. Its filename is
readahead-properly-shorten-readahead-when-falling-back-to-do_page_cache_ra.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/readahead-properly-shorten-readahead-when-falling-back-to-do_page_cache_ra.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: readahead: properly shorten readahead when falling back to do_page_cache_ra()
Date: Tue, 25 Jun 2024 12:18:53 +0200
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@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/readahead.c~readahead-properly-shorten-readahead-when-falling-back-to-do_page_cache_ra
+++ a/mm/readahead.c
@@ -491,7 +491,8 @@ void page_cache_ra_order(struct readahea
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 readahea
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);
}
/*
_
Patches currently in -mm which might be from jack@xxxxxxx are
revert-mm-writeback-fix-possible-divide-by-zero-in-wb_dirty_limits-again.patch
mm-avoid-overflows-in-dirty-throttling-logic.patch
readahead-make-sure-sync-readahead-reads-needed-page.patch
filemap-fix-page_cache_next_miss-when-no-hole-found.patch
readahead-properly-shorten-readahead-when-falling-back-to-do_page_cache_ra.patch
readahead-drop-pointless-index-from-force_page_cache_ra.patch
readahead-drop-index-argument-of-page_cache_async_readahead.patch
readahead-drop-dead-code-in-page_cache_ra_order.patch
readahead-drop-dead-code-in-ondemand_readahead.patch
readahead-disentangle-async-and-sync-readahead.patch
readahead-fold-try_context_readahead-into-its-single-caller.patch
readahead-simplify-gotos-in-page_cache_sync_ra.patch
