From: Liu Bo <bo.li.liu@oracle.com>
Date: Tue, 24 Jun 2014 07:39:16 +0000 (+0800)
Subject: Btrfs: fix crash when mounting raid5 btrfs with missing disks
X-Git-Tag: firefly_0821_release~176^2~3585^2~16
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=5588383ece6127909df5b9d601d562fe5b9fe38a;p=firefly-linux-kernel-4.4.55.git

Btrfs: fix crash when mounting raid5 btrfs with missing disks

The reproducer is

$ mkfs.btrfs D1 D2 D3 -mraid5
$ mkfs.ext4 D2 && mkfs.ext4 D3
$ mount D1 /btrfs -odegraded

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

[   87.672992] ------------[ cut here ]------------
[   87.673845] kernel BUG at fs/btrfs/raid56.c:1828!
...
[   87.673845] RIP: 0010:[<ffffffff813efc7e>]  [<ffffffff813efc7e>] __raid_recover_end_io+0x4ae/0x4d0
...
[   87.673845] Call Trace:
[   87.673845]  [<ffffffff8116bbc6>] ? mempool_free+0x36/0xa0
[   87.673845]  [<ffffffff813f0255>] raid_recover_end_io+0x75/0xa0
[   87.673845]  [<ffffffff81447c5b>] bio_endio+0x5b/0xa0
[   87.673845]  [<ffffffff81447cb2>] bio_endio_nodec+0x12/0x20
[   87.673845]  [<ffffffff81374621>] end_workqueue_fn+0x41/0x50
[   87.673845]  [<ffffffff813ad2aa>] normal_work_helper+0xca/0x2c0
[   87.673845]  [<ffffffff8108ba2b>] process_one_work+0x1eb/0x530
[   87.673845]  [<ffffffff8108b9c9>] ? process_one_work+0x189/0x530
[   87.673845]  [<ffffffff8108c15b>] worker_thread+0x11b/0x4f0
[   87.673845]  [<ffffffff8108c040>] ? rescuer_thread+0x290/0x290
[   87.673845]  [<ffffffff810939c4>] kthread+0xe4/0x100
[   87.673845]  [<ffffffff810938e0>] ? kthread_create_on_node+0x220/0x220
[   87.673845]  [<ffffffff817e7c7c>] ret_from_fork+0x7c/0xb0
[   87.673845]  [<ffffffff810938e0>] ? kthread_create_on_node+0x220/0x220

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

It's because that we miscalculate @rbio->bbio->error so that it doesn't
reach maximum of tolerable errors while it should have.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Tested-by: Satoru Takeuchi<takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
---

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 4055291a523e..4a88f073fdd7 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1956,9 +1956,10 @@ static int __raid56_parity_recover(struct btrfs_raid_bio *rbio)
 	 * pages are going to be uptodate.
 	 */
 	for (stripe = 0; stripe < bbio->num_stripes; stripe++) {
-		if (rbio->faila == stripe ||
-		    rbio->failb == stripe)
+		if (rbio->faila == stripe || rbio->failb == stripe) {
+			atomic_inc(&rbio->bbio->error);
 			continue;
+		}
 
 		for (pagenr = 0; pagenr < nr_pages; pagenr++) {
 			struct page *p;