This is a note to let you know that I've just added the patch titled
md/bitmap: always wait for writes on unplug.
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
md-bitmap-always-wait-for-writes-on-unplug.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4b5060ddae2b03c5387321fafc089d242225697a Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Tue, 9 Sep 2014 14:13:51 +1000
Subject: md/bitmap: always wait for writes on unplug.
From: NeilBrown <neilb@xxxxxxx>
commit 4b5060ddae2b03c5387321fafc089d242225697a upstream.
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 <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/bitmap.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -883,7 +883,6 @@ 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))
@@ -901,16 +900,13 @@ 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);
}
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-3.10/md-bitmap-always-wait-for-writes-on-unplug.patch
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