The patch titled
writeback: fix nr_to_write counter
has been removed from the -mm tree. Its filename was
writeback-fix-nr_to_write-counter.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: writeback: fix nr_to_write counter
From: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
Commit 05fe478dd04e02fa230c305ab9b5616669821dd3 ("mm: write_cache_pages
integrity fix") introduced some @wbc->nr_to_write breakage. Here is the
change from the commit:
>--- a/mm/page-writeback.c
>+++ b/mm/page-writeback.c
>@@ -963,8 +963,10 @@ retry:
> }
> }
>
> if (--nr_to_write <= 0)
> done = 1;
> if (wbc->sync_mode == WB_SYNC_NONE) {
> if (--wbc->nr_to_write <= 0)
> done = 1;
> }
> if (wbc->nonblocking && bdi_write_congested(bdi)) {
> wbc->encountered_congestion = 1;
> done = 1
> }
It made the following changes:
1. Decrement wbc->nr_to_write instead of nr_to_write
2. Decrement wbc->nr_to_write _only_ if wbc->sync_mode == WB_SYNC_NONE
3. If synced nr_to_write pages, stop only if if wbc->sync_mode ==
WB_SYNC_NONE, otherwise keep going.
However, according to the commit message, the intention was to only make
change 3. Change 1 is a bug. Change 2 does not seem to be necessary, and
it breaks UBIFS expectations, so if needed, it should be done separately
later. And change 2 does not seem to be documented in the commit message.
This patch does the following:
1. Undo changes 1 and 2
2. Add a comment explaining change 3 (it very useful to have comments
in _code_, not only in the commit).
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
Acked-by: Nick Piggin <npiggin@xxxxxxx>
Cc: Dave Kleikamp <shaggy@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff -puN mm/page-writeback.c~writeback-fix-nr_to_write-counter mm/page-writeback.c
--- a/mm/page-writeback.c~writeback-fix-nr_to_write-counter
+++ a/mm/page-writeback.c
@@ -1051,13 +1051,22 @@ continue_unlock:
}
}
- if (wbc->sync_mode == WB_SYNC_NONE) {
- wbc->nr_to_write--;
- if (wbc->nr_to_write <= 0) {
- done = 1;
- break;
- }
+ if (nr_to_write > 0)
+ nr_to_write--;
+ else if (wbc->sync_mode == WB_SYNC_NONE) {
+ /*
+ * We stop writing back only if we are not
+ * doing integrity sync. In case of integrity
+ * sync we have to keep going because someone
+ * may be concurrently dirtying pages, and we
+ * might have synced a lot of newly appeared
+ * dirty pages, but have not synced all of the
+ * old dirty pages.
+ */
+ done = 1;
+ break;
}
+
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
done = 1;
_
Patches currently in -mm which might be from Artem.Bityutskiy@xxxxxxxxx are
origin.patch
reiser4-vfs-add-super_operationssync_inodes-2.patch
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