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btrfs-progs: force overwrite should wipe stale SB

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(I am unable to reproduce the issue, tried to go back with progs versions
but still the same. So as of now this code remains untested, suggest to
wait till we have a reproducible test case).

Here is a test case which says it all..

mkfs.xfs -f $DEV
mkfs.btrfs -f $DEV
mount $DEV $MNT
mount: /dev/vdiskc: more filesystems detected. This should not happen,
       use -t <type> to explicitly specify the filesystem type or
       use wipefs(8) to clean up the device.

mount: you must specify the filesystem type

with this patch btrfs_prepare_device() also wipes old FS if any,
btrfs_prepare_device() is called after we have verified that
user has provided -f option.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Anand Jain 2014-10-02 07:22:09 +08:00 committed by David Sterba
parent 2c0e02a568
commit d0b24918f6
1 changed files with 38 additions and 0 deletions
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38
utils.c
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@ -678,6 +678,42 @@ int btrfs_add_to_fsid(struct btrfs_trans_handle *trans,
return 0;
}
static void btrfs_wipe_existing_sb(int fd)
{
const char *off = NULL;
size_t len = 0;
loff_t offset;
char buf[BUFSIZ];
int rc = 0;
blkid_probe pr = NULL;
pr = blkid_new_probe();
if (!pr)
return;
if (blkid_probe_set_device(pr, fd, 0, 0))
goto out;
rc = blkid_probe_lookup_value(pr, "SBMAGIC_OFFSET", &off, NULL);
if (!rc)
rc = blkid_probe_lookup_value(pr, "SBMAGIC", NULL, &len);
if (rc || len == 0 || off == NULL)
goto out;
offset = strtoll(off, NULL, 10);
if (len > sizeof(buf))
len = sizeof(buf);
memset(buf, 0, len);
rc = pwrite(fd, buf, len, offset);
fsync(fd);
out:
blkid_free_probe(pr);
return;
}
int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret,
u64 max_block_count, int *mixed, int discard)
{
@ -729,6 +765,8 @@ int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret,
return 1;
}
btrfs_wipe_existing_sb(fd);
*block_count_ret = block_count;
return 0;
}