From 4b5060ddae2b03c5387321fafc089d242225697a Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 9 Sep 2014 14:13:51 +1000 Subject: [PATCH] md/bitmap: always wait for writes on unplug. If two threads call bitmap_unplug at the same time, then one might schedule all the writes, and the other might decide that it doesn't need to wait. But really it does. It rarely hurts to wait when it isn't absolutely necessary, and the current code doesn't really focus on 'absolutely necessary' anyway. So just wait always. This can potentially lead to data corruption if a crash happens at an awkward time and data was written before the bitmap was updated. It is very unlikely, but this should go to -stable just to be safe. Appropriate for any -stable. Signed-off-by: NeilBrown Cc: stable@vger.kernel.org (please delay until 3.18 is released) --- drivers/md/bitmap.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index 67f8b31e2054..da3604e73e8a 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -879,7 +879,6 @@ void bitmap_unplug(struct bitmap *bitmap) { unsigned long i; int dirty, need_write; - int wait = 0; if (!bitmap || !bitmap->storage.filemap || test_bit(BITMAP_STALE, &bitmap->flags)) @@ -897,16 +896,13 @@ void bitmap_unplug(struct bitmap *bitmap) clear_page_attr(bitmap, i, BITMAP_PAGE_PENDING); write_page(bitmap, bitmap->storage.filemap[i], 0); } - if (dirty) - wait = 1; - } - if (wait) { /* if any writes were performed, we need to wait on them */ - if (bitmap->storage.file) - wait_event(bitmap->write_wait, - atomic_read(&bitmap->pending_writes)==0); - else - md_super_wait(bitmap->mddev); } + if (bitmap->storage.file) + wait_event(bitmap->write_wait, + atomic_read(&bitmap->pending_writes)==0); + else + md_super_wait(bitmap->mddev); + if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags)) bitmap_file_kick(bitmap); }