linux-toradex.git/drivers/md/dm-kcopyd.c, branch v3.3.6

dm kcopyd: add dm_kcopyd_zero to zero an area

2011-10-31T20:18:58+00:00

This patch introduces dm_kcopyd_zero() to make it easy to use
kcopyd to write zeros into the requested areas instead
instead of copying.  It is implemented by passing a NULL
copying source to dm_kcopyd_copy().

The forthcoming thin provisioning target uses this.

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

dm kcopyd: fix job_pool leak

2011-10-23T19:55:17+00:00

Fix memory leak introduced by commit a6e50b409d3f9e0833e69c3c9cca822e8fa4adbb
(dm snapshot: skip reading origin when overwriting complete chunk).

When allocating a set of jobs from kc->job_pool, job->master_job must be
set (to point to itself) so that the mempool item gets freed when the
master_job completes.

master_job was introduced by commit c6ea41fbbe08f270a8edef99dc369faf809d1bd6
(dm kcopyd: preallocate sub jobs to avoid deadlock)

Reported-by: Michael Leun 
Cc: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm snapshot: skip reading origin when overwriting complete chunk

2011-08-02T11:32:04+00:00

If we write a full chunk in the snapshot, skip reading the origin device
because the whole chunk will be overwritten anyway.

This patch changes the snapshot write logic when a full chunk is written.
In this case:
  1. allocate the exception
  2. dispatch the bio (but don't report the bio completion to device mapper)
  3. write the exception record
  4. report bio completed

Callbacks must be done through the kcopyd thread, because callbacks must not
race with each other.  So we create two new functions:

  dm_kcopyd_prepare_callback: allocate a job structure and prepare the callback.
  (This function must not be called from interrupt context.)

  dm_kcopyd_do_callback: submit callback.
  (This function may be called from interrupt context.)

Performance test (on snapshots with 4k chunk size):
  without the patch:
    non-direct-io sequential write (dd):    17.7MB/s
    direct-io sequential write (dd):        20.9MB/s
    non-direct-io random write (mkfs.ext2): 0.44s

  with the patch:
    non-direct-io sequential write (dd):    26.5MB/s
    direct-io sequential write (dd):        33.2MB/s
    non-direct-io random write (mkfs.ext2): 0.27s

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

dm kcopyd: remove nr_pages field from job structure

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

The nr_pages field in struct kcopyd_job is only used temporarily in
run_pages_job() to count the number of required pages.
We can use a local variable instead.

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

dm kcopyd: remove offset field from job structure

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

The offset field in struct kcopyd_job is always zero so remove it.

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

atomic: use

2011-07-26T23:49:47+00:00

This allows us to move duplicated code in 
(atomic_inc_not_zero() for now) to 

Signed-off-by: Arun Sharma 
Reviewed-by: Eric Dumazet 
Cc: Ingo Molnar 
Cc: David Miller 
Cc: Eric Dumazet 
Acked-by: Mike Frysinger 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dm kcopyd: return client directly and not through a pointer

2011-05-29T12:03:13+00:00

Return client directly from dm_kcopyd_client_create, not through a
parameter, making it consistent with dm_io_client_create.

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

dm kcopyd: reserve fewer pages

2011-05-29T12:03:11+00:00

Reserve just the minimum of pages needed to process one job.

Because we allocate pages from page allocator, we don't need to reserve
a large number of pages.  The maximum job size is SUB_JOB_SIZE and we
calculate the number of reserved pages based on this.

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

dm io: use fixed initial mempool size

2011-05-29T12:03:09+00:00

Replace the arbitrary calculation of an initial io struct mempool size
with a constant.

The code calculated the number of reserved structures based on the request
size and used a "magic" multiplication constant of 4.  This patch changes
it to reserve a fixed number - itself still chosen quite arbitrarily.
Further testing might show if there is a better number to choose.

Note that if there is no memory pressure, we can still allocate an
arbitrary number of "struct io" structures.  One structure is enough to
process the whole request.

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

dm kcopyd: alloc pages from the main page allocator

2011-05-29T12:03:07+00:00

This patch changes dm-kcopyd so that it allocates pages from the main
page allocator with __GFP_NOWARN | __GFP_NORETRY flags (so that it can
fail in case of memory pressure). If the allocation fails, dm-kcopyd
allocates pages from its own reserve.

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