linux.git/drivers/md/dm-snap.c, branch v2.6.27

dm snapshot: use per device mempools

2008-07-21T11:00:35+00:00

Change snapshot per-module mempool to per-device mempool.

Per-module mempools could cause a deadlock if multiple
snapshot devices are stacked above each other.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: fix race during exception creation

2008-07-21T11:00:34+00:00

Fix a race condition that returns incorrect data when a write causes an
exception to be allocated whilst a read is still in flight.

The race condition happens as follows:
* A read to non-reallocated sector in the snapshot is submitted so that the
  read is routed to the original device.
* A write to the original device is submitted. The write causes an exception
  that reallocates the block.  The write proceeds.
* The original read is dequeued and reads the wrong data.

This race can be triggered with CFQ scheduler and one thread writing and
multiple threads reading simultaneously.

(This patch relies upon the earlier dm-kcopyd-per-device.patch to avoid a
deadlock.)

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: track snapshot reads

2008-07-21T11:00:32+00:00

Whenever a snapshot read gets mapped through to the origin, track it in
a per-snapshot hash table indexed by chunk number, using memory allocated
from a new per-snapshot mempool.

We need to track these reads to avoid race conditions which will be fixed
by patches that follow.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: move include files

2008-04-25T12:26:55+00:00

Publish the dm-io, dm-log and dm-kcopyd headers in include/linux.

Signed-off-by: Alasdair G Kergon

dm kcopyd: clean interface

2008-04-25T12:26:44+00:00

Clean up the kcopyd interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm io: clean interface

2008-04-25T12:26:43+00:00

Clean up the dm-io interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm snapshot: store pointer to target instance

2008-04-25T12:26:40+00:00

Save pointer to dm_target in dm_snapshot structure.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: reduce default memory allocation

2008-04-25T12:26:35+00:00

Limit the amount of memory allocated per snapshot on systems
with a large page size.  (The larger default chunk size on
these systems compensates for the smaller number of pages reserved.)

Signed-off-by: Milan Broz 
Signed-off-by: Alasdair G Kergon

dm io: write error bits form long not int

2008-03-28T21:45:23+00:00

write_err is an unsigned long used with set_bit() so should not be passed
around as unsigned int.

http://bugzilla.kernel.org/show_bug.cgi?id=10271

Signed-off-by: Alasdair G Kergon 
Cc: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dm snapshot: combine consecutive exceptions in memory

2008-02-08T02:11:27+00:00

Provided sector_t is 64 bits, reduce the in-memory footprint of the
snapshot exception table by the simple method of using unused bits of
the chunk number to combine consecutive entries.

Signed-off-by: Milan Broz 
Signed-off-by: Alasdair G Kergon