Btrfs devel - May 2012 - [PATCH] Btrfs: fix crash in scrub repair code when device is missing

Fix that when scrub tries to repair an I/O or checksum error and one of
the devices containing the mirror is missing, it crashes in bio_add_page
because the bdev is a NULL pointer for missing devices.

Reported-by: Marco L. Crociani <marco.crociani@gmail.com>
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
---
 fs/btrfs/scrub.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index b679bf6..7e487be 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -998,6 +998,7 @@ static int scrub_setup_recheck_block(struct scrub_dev *sdev,
 			page = sblock->pagev + page_index;
 			page->logical = logical;
 			page->physical = bbio->stripes[mirror_index].physical;
+			/* for missing devices, bdev is NULL */
 			page->bdev = bbio->stripes[mirror_index].dev->bdev;
 			page->mirror_num = mirror_index + 1;
 			page->page = alloc_page(GFP_NOFS);
@@ -1042,6 +1043,12 @@ static int scrub_recheck_block(struct btrfs_fs_info
*fs_info,
 		struct scrub_page *page = sblock->pagev + page_num;
 		DECLARE_COMPLETION_ONSTACK(complete);
 
+		if (page->bdev == NULL) {
+			page->io_error = 1;
+			sblock->no_io_error_seen = 0;
+			continue;
+		}
+
 		BUG_ON(!page->page);
 		bio = bio_alloc(GFP_NOFS, 1);
 		if (!bio)
-- 
1.7.10.1.362.g242cab3

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On Thu, May 3, 2012 at 11:31 AM, Stefan Behrens
<sbehrens@giantdisaster.de> wrote:
> Fix that when scrub tries to repair an I/O or checksum error and one of
> the devices containing the mirror is missing, it crashes in bio_add_page
> because the bdev is a NULL pointer for missing devices.
>
> Reported-by: Marco L. Crociani <marco.crociani@gmail.com>
> Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
> ---
>  fs/btrfs/scrub.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index b679bf6..7e487be 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -998,6 +998,7 @@ static int scrub_setup_recheck_block(struct scrub_dev
*sdev,
>                        page = sblock->pagev + page_index;
>                        page->logical = logical;
>                        page->physical =
bbio->stripes[mirror_index].physical;
> +                       /* for missing devices, bdev is NULL */
>                        page->bdev =
bbio->stripes[mirror_index].dev->bdev;
>                        page->mirror_num = mirror_index + 1;
>                        page->page = alloc_page(GFP_NOFS);
> @@ -1042,6 +1043,12 @@ static int scrub_recheck_block(struct btrfs_fs_info
*fs_info,
>                struct scrub_page *page = sblock->pagev + page_num;
>                DECLARE_COMPLETION_ONSTACK(complete);
>
> +               if (page->bdev == NULL) {
> +                       page->io_error = 1;
> +                       sblock->no_io_error_seen = 0;
> +                       continue;
> +               }
> +
>                BUG_ON(!page->page);
>                bio = bio_alloc(GFP_NOFS, 1);
>                if (!bio)
> --
> 1.7.10.1.362.g242cab3
>
May  3 18:53:08 evo kernel: [ 5270.759254] btrfs: checksum error at
logical 756637261824 on dev /dev/sda3, sector 881151024, root 259,
inode 1821286, offset 325373952, length 4096, links 1 (path: [...])
May  3 18:53:08 evo kernel: [ 5270.759286] btrfs: unable to fixup
(regular) error at logical 756637261824 on dev /dev/sda3


scrub device /dev/sda3 (id 1) status
	scrub started at Thu May  3 17:30:35 2012, running for 6594 seconds
	total bytes scrubbed: 568.65GB with 1 errors
	error details: csum=1
	corrected errors: 0, uncorrectable errors: 1, unverified errors: 0
scrub device  (id 2) history
	scrub started at Thu May  3 17:30:35 2012 and finished after 0 seconds
	total bytes scrubbed: 0.00 with 0 errors
scrub device /dev/sdb3 (id 3) status
	scrub started at Thu May  3 17:30:35 2012, running for 6594 seconds
	total bytes scrubbed: 536.66GB with 0 errors

May  3 20:07:51 evo kernel: [ 9752.940360] btrfs: checksum error at
logical 1284041527296 on dev /dev/sda3, sector 1907567464, root 259,
inode 1327815, offset 1691832320, length 4096, links 1 (path: [...])
May  3 20:07:51 evo kernel: [ 9752.940392] btrfs: unable to fixup
(regular) error at logical 1284041527296 on dev /dev/sda3
May  3 20:25:45 evo kernel: [10826.760001] btrfs: checksum error at
logical 1378644791296 on dev /dev/sda3, sector 2092339464, root 259,
inode 1759403, offset 767893504, length 4096, links 1 (path: [...])
May  3 20:25:45 evo kernel: [10826.760025] btrfs: unable to fixup
(regular) error at logical 1378644791296 on dev /dev/sda3
May  3 20:27:04 evo kernel: [10905.612849] btrfs: checksum error at
logical 1386199773184 on dev /dev/sda3, sector 2107095288, root 259,
inode 1580366, offset 1526546432, length 4096, links 1 (path: [...])
May  3 20:27:04 evo kernel: [10905.612881] btrfs: unable to fixup
(regular) error at logical 1386199773184 on dev /dev/sda3
May  3 20:29:46 evo kernel: [11067.396252] btrfs: checksum error at
logical 1401913339904 on dev /dev/sda3, sector 2137785848, root 259,
inode 1851460, offset 515543040, length 4096, links 1 (path: [...])
May  3 20:29:46 evo kernel: [11067.408660] btrfs: unable to fixup
(regular) error at logical 1401913339904 on dev /dev/sda3

That patch worked for me.
Thanks!

-- 
Marco Lorenzo Crociani,
marco.crociani@gmail.com
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