linux-toradex.git/drivers/md/dm-snap-persistent.c, branch v3.14.46

dm snapshot: fix metadata corruption

2014-03-03T22:58:13+00:00

Commit 55494bf2947dccdf2 ("dm snapshot: use dm-bufio") broke snapshots.
Before that 3.14-rc1 commit, loading a snapshot's list of exceptions
involved reading exception areas one by one into ps->area and inserting
those exceptions into the hash table.  Commit 55494bf2947dccdf2 changed
it so that dm-bufio with prefetch is used to load exceptions in batchs.
Exceptions are loaded correctly, but ps->area is left uninitialized.
When a new exception is allocated, it is stored in this uninitialized
ps->area which will be written to the disk.  This causes metadata
corruption.

Fix this corruption by copying the last area that was read via dm-bufio
into ps->area.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm snapshot: use dm-bufio prefetch

2014-01-15T04:23:03+00:00

This patch modifies dm-snapshot so that it prefetches the buffers when
loading the exceptions.

The number of buffers read ahead is specified in the DM_PREFETCH_CHUNKS
macro.  The current value for DM_PREFETCH_CHUNKS (12) was found to
provide the best performance on a single 15k SCSI spindle.  In the
future we may modify this default or make it configurable.

Also, introduce the function dm_bufio_set_minimum_buffers to setup
bufio's number of internal buffers before freeing happens.  dm-bufio may
hold more buffers if enough memory is available.  There is no guarantee
that the specified number of buffers will be available - if you need a
guarantee, use the argument reserved_buffers for
dm_bufio_client_create.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm snapshot: use dm-bufio

2014-01-15T04:23:02+00:00

Use dm-bufio for initial loading of the exceptions.
Introduce a new function dm_bufio_forget that frees the given buffer.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm snapshot: prepare for switch to using dm-bufio

2014-01-14T18:38:32+00:00

Change the functions get_exception, read_exception and insert_exceptions
so that ps->area is passed as an argument.

This patch doesn't change any functionality, but it refactors the code
to allow for a cleaner switch over to using dm-bufio.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm snapshot: call destroy_work_on_stack() to pair with INIT_WORK_ONSTACK()

2014-01-07T15:31:34+00:00

In case CONFIG_DEBUG_OBJECTS_WORK is defined, it is needed to
call destroy_work_on_stack() which frees the debug object to pair
with INIT_WORK_ONSTACK().

Signed-off-by: Liu, Chuansheng 
Signed-off-by: Mike Snitzer

dm snapshot: fix data corruption

2013-10-16T02:17:47+00:00

This patch fixes a particular type of data corruption that has been
encountered when loading a snapshot's metadata from disk.

When we allocate a new chunk in persistent_prepare, we increment
ps->next_free and we make sure that it doesn't point to a metadata area
by further incrementing it if necessary.

When we load metadata from disk on device activation, ps->next_free is
positioned after the last used data chunk. However, if this last used
data chunk is followed by a metadata area, ps->next_free is positioned
erroneously to the metadata area. A newly-allocated chunk is placed at
the same location as the metadata area, resulting in data or metadata
corruption.

This patch changes the code so that ps->next_free skips the metadata
area when metadata are loaded in function read_exceptions.

The patch also moves a piece of code from persistent_prepare_exception
to a separate function skip_metadata to avoid code duplication.

CVE-2013-4299

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

dm snapshot: workaround for a false positive lockdep warning

2013-09-20T14:36:34+00:00

The kernel reports a lockdep warning if a snapshot is invalidated because
it runs out of space.

The lockdep warning was triggered by commit 0976dfc1d0cd80a4e9dfaf87bd87
("workqueue: Catch more locking problems with flush_work()") in v3.5.

The warning is false positive.  The real cause for the warning is that
the lockdep engine treats different instances of md->lock as a single
lock.

This patch is a workaround - we use flush_workqueue instead of flush_work.
This code path is not performance sensitive (it is called only on
initialization or invalidation), thus it doesn't matter that we flush the
whole workqueue.

The real fix for the problem would be to teach the lockdep engine to treat
different instances of md->lock as separate locks.

Signed-off-by: Mikulas Patocka 
Acked-by: Alasdair G Kergon 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org # 3.5+

md: Add in export.h for files using EXPORT_SYMBOL

2011-10-31T23:31:19+00:00

These files were getting the defines for EXPORT_SYMBOL because
device.h was including module.h.  But we are going to put an
end to that.  So add the proper export.h include now.

Signed-off-by: Paul Gortmaker

dm snapshot: style cleanups

2011-08-02T11:32:03+00:00

Coding style cleanups.

Signed-off-by: Alasdair G Kergon 
Signed-off-by: Jonathan Brassow

dm: use vzalloc

2011-08-02T11:32:02+00:00

Use vzalloc() instead of vmalloc()+memset().

Signed-off-by: Joe Perches 
Signed-off-by: Alasdair G Kergon