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Btrfs: fix parity scrub of RAID 5/6 with missing device

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When testing the previous patch, Zhao Lei reported a similar bug when
attempting to scrub a degraded RAID 5/6 filesystem with a missing
device, leading to NULL pointer dereferences from the RAID 5/6 parity
scrubbing code.

The first cause was the same as in the previous patch: attempting to
call bio_add_page() on a missing block device. To fix this,
scrub_extent_for_parity() can just mark the sectors on the missing
device as errors instead of attempting to read from it.

Additionally, the code uses scrub_remap_extent() to map the extent of
the corresponding data stripe, but the extent wasn't already mapped. If
scrub_remap_extent() finds a missing block device, it doesn't initialize
extent_dev, so we're left with a NULL struct btrfs_device. The solution
is to use btrfs_map_block() directly.

Reported-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Omar Sandoval 2015-06-19 11:52:52 -07:00 committed by Chris Mason
parent 73ff61dbe5
commit 4a770891d9
1 changed files with 22 additions and 4 deletions
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26
fs/btrfs/scrub.c
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@ -2696,6 +2696,11 @@ static int scrub_extent_for_parity(struct scrub_parity *sparity,
u8 csum[BTRFS_CSUM_SIZE];
u32 blocksize;
if (dev->missing) {
scrub_parity_mark_sectors_error(sparity, logical, len);
return 0;
}
if (flags & BTRFS_EXTENT_FLAG_DATA) {
blocksize = sctx->sectorsize;
} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
@ -2905,6 +2910,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
struct btrfs_root *root = fs_info->extent_root;
struct btrfs_root *csum_root = fs_info->csum_root;
struct btrfs_extent_item *extent;
struct btrfs_bio *bbio = NULL;
u64 flags;
int ret;
int slot;
@ -2914,6 +2920,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
u64 extent_logical;
u64 extent_physical;
u64 extent_len;
u64 mapped_length;
struct btrfs_device *extent_dev;
struct scrub_parity *sparity;
int nsectors;
@ -3037,10 +3044,21 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
scrub_parity_mark_sectors_data(sparity, extent_logical,
extent_len);
scrub_remap_extent(fs_info, extent_logical,
extent_len, &extent_physical,
&extent_dev,
&extent_mirror_num);
mapped_length = extent_len;
ret = btrfs_map_block(fs_info, READ, extent_logical,
&mapped_length, &bbio, 0);
if (!ret) {
if (!bbio || mapped_length < extent_len)
ret = -EIO;
}
if (ret) {
btrfs_put_bbio(bbio);
goto out;
}
extent_physical = bbio->stripes[0].physical;
extent_mirror_num = bbio->mirror_num;
extent_dev = bbio->stripes[0].dev;
btrfs_put_bbio(bbio);
ret = btrfs_lookup_csums_range(csum_root,
extent_logical,