Messages in this thread Patch in this message | | | Date | Fri, 13 Feb 2009 16:58:25 -0800 | From | Greg KH <> | Subject | [patch 11/47] write-back: fix nr_to_write counter |
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2.6.27-stable review patch. If anyone has any objections, please let us know.
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From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
commit dcf6a79dda5cc2a2bec183e50d829030c0972aaa upstream.
Commit 05fe478dd04e02fa230c305ab9b5616669821dd3 introduced some @wbc->nr_to_write breakage.
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@nokia.com> Acked-by: Nick Piggin <npiggin@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- mm/page-writeback.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
--- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -985,13 +985,22 @@ continue_unlock: } } - if (wbc->sync_mode == WB_SYNC_NONE) { + if (wbc->nr_to_write > 0) wbc->nr_to_write--; - if (wbc->nr_to_write <= 0) { - done = 1; - break; - } + 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;
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