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writeback: only update ->writeback_index for range_cyclic writeback

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mapping->writeback_index is only [1] used as the starting point for
range_cyclic writeback, so there is no point in updating it for other
types of writeback.

[1] except for btrfs_defrag_file which does really odd things with
mapping->writeback_index.  But btrfs doesn't use write_cache_pages at all,
so this isn't relevant here.

Link: https://lkml.kernel.org/r/20240215063649.2164017-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2024-02-15 07:36:40 +01:00 committed by Andrew Morton
parent 9810325854
commit 5d899d43ed
1 changed files with 14 additions and 10 deletions
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24
mm/page-writeback.c
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@ -2403,7 +2403,6 @@ int write_cache_pages(struct address_space *mapping,
pgoff_t index;
pgoff_t end; /* Inclusive */
pgoff_t done_index;
int range_whole = 0;
xa_mark_t tag;
folio_batch_init(&fbatch);
@ -2413,8 +2412,6 @@ int write_cache_pages(struct address_space *mapping,
} else {
index = wbc->range_start >> PAGE_SHIFT;
end = wbc->range_end >> PAGE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
}
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
tag_pages_for_writeback(mapping, index, end);
@ -2518,14 +2515,21 @@ int write_cache_pages(struct address_space *mapping,
}
/*
* If we hit the last page and there is more work to be done: wrap
* back the index back to the start of the file for the next
* time we are called.
* For range cyclic writeback we need to remember where we stopped so
* that we can continue there next time we are called. If we hit the
* last page and there is more work to be done, wrap back to the start
* of the file.
*
* For non-cyclic writeback we always start looking up at the beginning
* of the file if we are called again, which can only happen due to
* -ENOMEM from the file system.
*/
if (wbc->range_cyclic && !done)
done_index = 0;
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = done_index;
if (wbc->range_cyclic) {
if (done)
mapping->writeback_index = done_index;
else
mapping->writeback_index = 0;
}
return ret;
}