Eric Lee / smarc-fsl-linux-kernel

01 Nov, 2011

1 commit

  • 7f0696539   dm kcopyd: add dm_kcopyd_zero to zero an area ... Browse Code »

    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

    Mikulas Patocka
     

02 Aug, 2011

1 commit

  • a6e50b409   dm snapshot: skip reading origin when overwriting complete chunk ... Browse Code »

    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

    Mikulas Patocka
     

29 May, 2011

2 commits

25 Apr, 2008

1 commit