linux-toradex.git/drivers/md/dm-snap-persistent.c, branch v2.6.35-rc6

dm snapshot: persistent annotate work_queue as on stack

2010-02-16T18:42:51+00:00

chunk_io() declares its 'struct mdata_req' on the stack and then
initializes its 'struct work_struct' member.  Annotate the
initialization of this workqueue with INIT_WORK_ON_STACK to suppress a
debugobjects warning seen when CONFIG_DEBUG_OBJECTS_WORK is enabled.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm exception store: add merge specific methods

2009-12-10T23:52:29+00:00

Add functions that decide how many consecutive chunks of snapshot to
merge back into the origin next and to update the metadata afterwards.

prepare_merge provides a pointer to the most recent still-to-be-merged
chunk and returns how many previous ones are consecutive and can be
processed together.

commit_merge removes the nr_merged most-recent chunks permanently from
the exception store.  The number must not exceed that returned by
prepare_merge.

Introduce NUM_SNAPSHOT_HDR_CHUNKS to show where the snapshot header
chunk is accounted for.

Signed-off-by: Mikulas Patocka 
Reviewed-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm snapshot: move cow ref from exception store to snap core

2009-12-10T23:52:12+00:00

Store the reference to the snapshot cow device in the core snapshot
code instead of each exception store.  It can be accessed through the
new function dm_snap_cow().  Exception stores should each now maintain a
reference to their parent snapshot struct.

This is cleaner and makes part of the forthcoming snapshot merge code simpler.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon 
Reviewed-by: Jonathan Brassow 
Cc: Mikulas Patocka

dm snapshot: add allocated metadata to snapshot status

2009-12-10T23:52:11+00:00

Add number of sectors used by metadata to the end of the snapshot's status
line.

Renamed dm_exception_store_type's 'fraction_full' to 'usage'.  Renamed
arguments to be clearer about what is being returned.  Also added
'metadata_sectors'.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm snapshot: rename dm_snap_exception to dm_exception

2009-12-10T23:52:10+00:00

The exception structure is not necessarily just a snapshot
element (especially after we pull it out of dm-snap.c).

Renaming appropriately.

Signed-off-by: Jonathan Brassow 
Reviewed-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm snapshot: avoid else clause in persistent_read_metadata

2009-12-10T23:52:07+00:00

Minor code touch-up.  We don't need the 'else'.

Signed-off-by: Jonathan Brassow 
Reviewed-by: Mikulas Patocka 
Reviewed-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm snapshot: use unsigned integer chunk size

2009-10-16T22:18:17+00:00

Use unsigned integer chunk size.

Maximum chunk size is 512kB, there won't ever be need to use 4GB chunk size,
so the number can be 32-bit. This fixes compiler failure on 32-bit systems
with large block devices.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Reviewed-by: Jonathan Brassow 
Signed-off-by: Alasdair G Kergon

dm snapshot: fix on disk chunk size validation

2009-09-04T19:40:43+00:00

Fix some problems seen in the chunk size processing when activating a
pre-existing snapshot.

For a new snapshot, the chunk size can either be supplied by the creator
or a default value can be used.  For an existing snapshot, the
chunk size in the snapshot header on disk should always be used.

If someone attempts to load an existing snapshot and has the 'default
chunk size' option set, the kernel uses its default value even when it
is incorrect for the snapshot being loaded.  This patch ensures the
correct on-disk value is always used.

Secondly, when the code does use the chunk size stored on the disk it is
prudent to revalidate it, so the code can exit cleanly if it got
corrupted as happened in
https://bugzilla.redhat.com/show_bug.cgi?id=461506 .

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: fix header corruption race on invalidation

2009-09-04T19:40:39+00:00

If a persistent snapshot fills up, a race can corrupt the on-disk header
which causes a crash on any future attempt to activate the snapshot
(typically while booting).  This patch fixes the race.

When the snapshot overflows, __invalidate_snapshot is called, which calls
snapshot store method drop_snapshot. It goes to persistent_drop_snapshot that
calls write_header. write_header constructs the new header in the "area"
location.

Concurrently, an existing kcopyd job may finish, call copy_callback
and commit_exception method, that goes to persistent_commit_exception.
persistent_commit_exception doesn't do locking, relying on the fact that
callbacks are single-threaded, but it can race with snapshot invalidation and
overwrite the header that is just being written while the snapshot is being
invalidated.

The result of this race is a corrupted header being written that can
lead to a crash on further reactivation (if chunk_size is zero in the
corrupted header).

The fix is to use separate memory areas for each.

See the bug: https://bugzilla.redhat.com/show_bug.cgi?id=461506

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: refactor zero_disk_area to use chunk_io

2009-09-04T19:40:37+00:00

Refactor chunk_io to prepare for the fix in the following patch.

Pass an area pointer to chunk_io and simplify zero_disk_area to use
chunk_io.  No functional change.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon