On 28.03.2018 02:39, Anand Jain wrote:
> During the scan context, we aren't verifying the superblock-
> checksum when read.
> This patch fixes it by adding the checksum verification function
> btrfs_check_super_csum() in the function btrfs_read_disk_super().
> And makes device scan to error fail if the primary superblock csum
> is wrong, whereas if the copy-superblock csum is wrong it will just
> just report mismatch and continue mount/scan as usual. When the
Where in this patch do you deal with the secondary sb.
btrfs_read_disk_super verifies only the primary sb which corresponds to
the first part of the sentence. But I'm confused about the second?
I also think that 4/8 should be merged into this one.
> mount is successful We anyway overwrite all superblocks upon unmount.
>
> The context in which this will be called is - device scan, device ready,
> and mount -o device option.
>
> Test script:
>
> Corrupt primary superblock and check if device scan and mount
> fails:
> mkfs.btrfs -fq /dev/sdc
> dd if=/dev/urandom of=/dev/sdc ibs=1 obs=1 count=1 seek=64K
> btrfs dev scan /dev/sdc
> mount /dev/sdc /btrfs
>
> Corrupt secondary superblock and check if device scan and mount
> is succcessful, check for the dmesg for errors.
> mkfs.btrfs -fq /dev/sdc
> dd if=/dev/urandom of=/dev/sdc ibs=1 obs=1 count=1 seek=67108864
> btrfs dev scan /dev/sdc
> mount /dev/sdc /btrfs
>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> v1->v2:
> changed title.
> use explicit (< 0) check for %errr.
> Un-split pr_err() string.
> Fix typo in the git commit log.
> Move the csum check after bytenr and btrfs magic verified.
>
> fs/btrfs/volumes.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index b099823f60d1..eda86ba258fc 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1149,6 +1149,7 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
> struct page **page,
> struct btrfs_super_block **disk_super)
> {
> + int err;
> void *p;
> pgoff_t index;
>
> @@ -1183,6 +1184,18 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
> return -EINVAL;
> }
>
> + err = btrfs_check_super_csum((char *) *disk_super);
> + if (err < 0) {
> + if (err == -EINVAL)
> + pr_err("BTRFS error (device %pg): unsupported checksum type, bytenr=%llu",
> + bdev, bytenr);
> + else
> + pr_err("BTRFS error (device %pg): superblock checksum failed, bytenr=%llu",
> + bdev, bytenr);
> + btrfs_release_disk_super(*page);
> + return err;
> + }
> +
> if ((*disk_super)->label[0] &&
> (*disk_super)->label[BTRFS_LABEL_SIZE - 1])
> (*disk_super)->label[BTRFS_LABEL_SIZE - 1] = '\0';
>
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