linux-kernel - [ 53/59] md/bitmap: prevent bitmap_daemon_work running while initialising bitmap

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Message-Id: <20120419210615.671059149@linuxfoundation.org>
Date:	Thu, 19 Apr 2012 14:07:04 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, NeilBrown <neilb@...e.de>
Subject: [ 53/59] md/bitmap: prevent bitmap_daemon_work running while initialising bitmap

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.de>

commit afbaa90b80b1ec66e5137cc3824746bfdf559b18 upstream.

If a bitmap is added while the array is active, it is possible
for bitmap_daemon_work to run while the bitmap is being
initialised.
This is particularly a problem if bitmap_daemon_work sees
bitmap->filemap as non-NULL before it has been filled in properly.
So hold bitmap_info.mutex while filling in ->filemap
to prevent problems.

This patch is suitable for any -stable kernel, though it might not
apply cleanly before about 3.1.

Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/bitmap.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1897,7 +1897,9 @@ int bitmap_load(mddev_t *mddev)
 			 * re-add of a missing device */
 			start = mddev->recovery_cp;
 
+		mutex_lock(&mddev->bitmap_info.mutex);
 		err = bitmap_init_from_disk(bitmap, start);
+		mutex_unlock(&mddev->bitmap_info.mutex);
 	}
 	if (err)
 		goto out;


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