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Revert "readahead: properly shorten readahead when falling back to do_page_cache_ra()"

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This reverts commit 7c877586da.

Anders and Philippe have reported that recent kernels occasionally hang
when used with NFS in readahead code.  The problem has been bisected to
7c877586da ("readahead: properly shorten readahead when falling back to
do_page_cache_ra()").  The cause of the problem is that ra->size can be
shrunk by read_pages() call and subsequently we end up calling
do_page_cache_ra() with negative (read huge positive) number of pages. 
Let's revert 7c877586da for now until we can find a proper way how the
logic in read_pages() and page_cache_ra_order() can coexist.  This can
lead to reduced readahead throughput due to readahead window confusion but
that's better than outright hangs.

Link: https://lkml.kernel.org/r/20241126145208.985-1-jack@suse.cz
Fixes: 7c877586da ("readahead: properly shorten readahead when falling back to do_page_cache_ra()")
Reported-by: Anders Blomdell <anders.blomdell@gmail.com>
Reported-by: Philippe Troin <phil@fifi.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Philippe Troin <phil@fifi.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jan Kara 2024-11-26 15:52:08 +01:00 committed by Andrew Morton
parent 4a475c0a7e
commit a220d6b95b
1 changed files with 2 additions and 3 deletions
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5
mm/readahead.c
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@ -458,8 +458,7 @@ 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 start = readahead_index(ractl);
pgoff_t index = start;
pgoff_t index = readahead_index(ractl);
unsigned int min_order = mapping_min_folio_order(mapping);
pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT;
pgoff_t mark = index + ra->size - ra->async_size;
@ -522,7 +521,7 @@ void page_cache_ra_order(struct readahead_control *ractl,
if (!err)
return;
fallback:
do_page_cache_ra(ractl, ra->size - (index - start), ra->async_size);
do_page_cache_ra(ractl, ra->size, ra->async_size);
}
static unsigned long ractl_max_pages(struct readahead_control *ractl,