If one of the copy of the superblock is zero it does not
confirm to us that btrfs isn't there on that disk. When
we are having more than one copy of superblock we should
rather let the for loop to continue to check other copies.
the following test case and results would justify the
fix
mkfs.btrfs /dev/sdb /dev/sdc -f
mount /dev/sdb /btrfs
dd if=/dev/zero bs=1 count=8 of=/dev/sdc seek=$((64*1024+64))
~/before/btrfs-select-super -s 1 /dev/sdc
using SB copy 1, bytenr 67108864
here btrfs-select-super just wrote superblock to a mounted btrfs
with the fix:
./btrfs-select-super -s 1 /dev/sdc
/dev/sdc is currently mounted. Aborting.
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
disk-io.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/disk-io.c b/disk-io.c
index 589b37a..3f85c21 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -1138,9 +1138,12 @@ int btrfs_read_dev_super(int fd, struct
btrfs_super_block *sb, u64 sb_bytenr,
if (btrfs_super_bytenr(&buf) != bytenr )
continue;
- /* if magic is NULL, the device was removed */
- if (buf.magic == 0 && i == 0)
- return -1;
+ /* if magic is NULL, either the device was removed
+ * OR user / application inflected the disk albeit
+ * with the most common zeros.
+ * so only this doesn't confirm that this disk
+ * isn't part of btrfs
+ */
if (buf.magic != cpu_to_le64(BTRFS_MAGIC))
continue;
--
1.8.1.227.g44fe835
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