dm snapshot: don't invalidate on-disk image on snapshot write overflow
authorMikulas Patocka <mpatocka@redhat.com>
Sun, 21 Jun 2015 20:31:33 +0000 (16:31 -0400)
committerMike Snitzer <snitzer@redhat.com>
Wed, 12 Aug 2015 20:22:55 +0000 (16:22 -0400)
commit76c44f6d80e151d230844db7ffc058ac21b9e3f2
tree5fe3d4b62dad06b373f9d12e07a1b15884e7c43d
parentfc0a446152877d3a4e40166ddb19b6e0cb5f6567
dm snapshot: don't invalidate on-disk image on snapshot write overflow

When the snapshot overflows because of a write to the origin, the on-disk
image has to be invalidated.  However, when the snapshot overflows because
of a write to the snapshot, the on-disk image doesn't have to be
invalidated.  Change the behavior so that the on-disk image is not
invalidated in this case.

When the snapshot overflows, the variable snapshot_overflowed is set.
All writes to the snapshot are disallowed to minimize filesystem
corruption - this condition is cleared when the snapshot is deactivated
and activated.

The user can extend the overflowed snapshot, deactivate and activate it
again, run fsck (if journaling filesystem is not used) mount it and
recover the data.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
drivers/md/dm-snap.c