The patch titled
Subject: writeback: only update ->writeback_index for range_cyclic writeback
has been added to the -mm mm-unstable branch. Its filename is
writeback-only-update-writeback_index-for-range_cyclic-writeback.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/writeback-only-update-writeback_index-for-range_cyclic-writeback.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: Christoph Hellwig <hch@xxxxxx>
Subject: writeback: only update ->writeback_index for range_cyclic writeback
Date: Thu, 15 Feb 2024 07:36:40 +0100
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@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Acked-by: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
--- a/mm/page-writeback.c~writeback-only-update-writeback_index-for-range_cyclic-writeback
+++ a/mm/page-writeback.c
@@ -2403,7 +2403,6 @@ int write_cache_pages(struct address_spa
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_spa
} 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 @@ continue_unlock:
}
/*
- * 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;
}
_
Patches currently in -mm which might be from hch@xxxxxx are
writeback-dont-call-mapping_set_error-on-aop_writepage_activate.patch
writeback-fix-done_index-when-hitting-the-wbc-nr_to_write.patch
writeback-also-update-wbc-nr_to_write-on-writeback-failure.patch
writeback-only-update-writeback_index-for-range_cyclic-writeback.patch
writeback-rework-the-loop-termination-condition-in-write_cache_pages.patch
writeback-add-a-writeback-iterator.patch
