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Btrfs-progs: Initialize stripesize to the value of sectorsize

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stripesize should ideally be set to the value of sectorsize. However
previous versions of btrfs-progs/mkfs.btrfs had set stripesize to a
value of 4096. On machines with PAGE_SIZE other than 4096, This could
lead to the following scenario,

- /dev/loop0, /dev/loop1 and /dev/loop2 are mounted as a single
  filesystem. The filesystem was created by an older version of mkfs.btrfs
  which set stripesize to 4k.
- losetup -a
   /dev/loop0: [0030]:19477 (/root/disk-imgs/file-0.img)
   /dev/loop1: [0030]:16577 (/root/disk-imgs/file-1.img)
   /dev/loop2: [64770]:3423229 (/root/disk-imgs/file-2.img)
- /etc/mtab lists only /dev/loop0
- losetup /dev/loop4 /root/disk-imgs/file-1.img
  The new mkfs.btrfs invoked as 'mkfs.btrfs -f /dev/loop4' succeeds even
  though /dev/loop1 has already been mounted and has
  /root/disk-imgs/file-1.img as its backing file.

The above behaviour occurs because check_super() function returns an
error code (due to stripesize not being set to 4096) and hence
check_mounted_where() function treats /dev/loop1 as a disk containing a
filesystem other than Btrfs.

Hence as a workaround this commit allows 4096 as a valid stripesize.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Chandan Rajendra 2016-06-17 11:07:54 +05:30 committed by David Sterba
parent df05c7ed45
commit 49ec1413a7
2 changed files with 3 additions and 1 deletions
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3
disk-io.c
View File

@ -1476,7 +1476,8 @@ static int check_super(struct btrfs_super_block *sb)
error("invalid bytes_used %llu", btrfs_super_bytes_used(sb)); error("invalid bytes_used %llu", btrfs_super_bytes_used(sb));
goto error_out; goto error_out;
} }
if (btrfs_super_stripesize(sb) != 4096) { if ((btrfs_super_stripesize(sb) != 4096)
&& (btrfs_super_stripesize(sb) != btrfs_super_sectorsize(sb))) {
error("invalid stripesize %u", btrfs_super_stripesize(sb)); error("invalid stripesize %u", btrfs_super_stripesize(sb));
goto error_out; goto error_out;
} }

1
mkfs.c
View File

@ -1482,6 +1482,7 @@ int main(int argc, char **argv)
} }
sectorsize = max(sectorsize, (u32)sysconf(_SC_PAGESIZE)); sectorsize = max(sectorsize, (u32)sysconf(_SC_PAGESIZE));
stripesize = sectorsize;
saved_optind = optind; saved_optind = optind;
dev_cnt = argc - optind; dev_cnt = argc - optind;
if (dev_cnt == 0) if (dev_cnt == 0)