redonkable/alistair23-linux
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alistair23-linux/drivers/md
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Mikulas Patocka a6e50b409d dm snapshot: skip reading origin when overwriting complete chunk 
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 <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2011-08-02 12:32:04 +01:00
..
bitmap.c MD bitmap: Revert DM dirty log hooks 2011-07-27 11:00:37 +10:00
bitmap.h MD bitmap: Revert DM dirty log hooks 2011-07-27 11:00:37 +10:00
dm-bio-record.h dm: preserve bi_io_vec when resubmitting bios 2009-04-02 19:55:23 +01:00
dm-crypt.c dm: suppress endian warnings 2011-08-02 12:32:01 +01:00
dm-delay.c dm: convert workqueues to alloc_ordered 2011-01-13 19:59:57 +00:00
dm-exception-store.c dm snapshot: test chunk size against both origin and snapshot 2010-08-12 04:13:51 +01:00
dm-exception-store.h dm snapshot: test chunk size against both origin and snapshot 2010-08-12 04:13:51 +01:00
dm-flakey.c dm: add flakey target 2011-03-24 13:54:24 +00:00
dm-io.c dm io: flush cpu cache with vmapped io 2011-08-02 12:32:01 +01:00
dm-ioctl.c dm ioctl: prevent empty message 2011-08-02 12:32:03 +01:00
dm-kcopyd.c dm snapshot: skip reading origin when overwriting complete chunk 2011-08-02 12:32:04 +01:00
dm-linear.c dm: use dm_target_offset macro 2010-08-12 04:14:11 +01:00
dm-log-userspace-base.c dm log: userspace use list_move 2011-08-02 12:32:02 +01:00
dm-log-userspace-transfer.c netlink: kill eff_cap from struct netlink_skb_parms 2011-03-03 13:32:07 -08:00
dm-log-userspace-transfer.h dm log: userspace add luid to distinguish between concurrent log instances 2009-09-04 20:40:34 +01:00
dm-log.c dm: use vzalloc 2011-08-02 12:32:02 +01:00
dm-mpath.c dm mpath: fix potential NULL pointer in feature arg processing 2011-08-02 12:32:00 +01:00
dm-mpath.h dm mpath: remove is_active from struct dm_path 2008-10-10 13:36:58 +01:00
dm-path-selector.c dm: path selector use module refcount directly 2009-04-02 19:55:27 +01:00
dm-path-selector.h dm mpath: add start_io and nr_bytes to path selectors 2009-06-22 10:12:27 +01:00
dm-queue-length.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
dm-raid.c dm raid: tidy includes 2011-08-02 12:32:03 +01:00
dm-raid1.c dm kcopyd: return client directly and not through a pointer 2011-05-29 13:03:13 +01:00
dm-region-hash.c Fix common misspellings 2011-03-31 11:26:23 -03:00
dm-round-robin.c dm mpath: add start_io and nr_bytes to path selectors 2009-06-22 10:12:27 +01:00
dm-service-time.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
dm-snap-persistent.c dm snapshot: style cleanups 2011-08-02 12:32:03 +01:00
dm-snap-transient.c dm snapshot: move cow ref from exception store to snap core 2009-12-10 23:52:12 +00:00
dm-snap.c dm snapshot: skip reading origin when overwriting complete chunk 2011-08-02 12:32:04 +01:00
dm-stripe.c dm stripe: implement merge method 2011-03-24 13:54:35 +00:00
dm-sysfs.c Driver core: Constify struct sysfs_ops in struct kobj_type 2010-03-07 17:04:49 -08:00
dm-table.c dm: ignore merge_bvec for snapshots when safe 2011-08-02 12:32:04 +01:00
dm-target.c dm: error return error for discards 2010-08-12 04:14:14 +01:00
dm-uevent.c dm table: remove dm_get from dm_table_get_md 2010-03-06 02:29:52 +00:00
dm-uevent.h dm: uevent generate events 2007-10-20 02:01:26 +01:00
dm-zero.c dm: zero silently drop discards 2010-08-12 04:14:12 +01:00
dm.c dm: ignore merge_bvec for snapshots when safe 2011-08-02 12:32:04 +01:00
dm.h dm: ignore merge_bvec for snapshots when safe 2011-08-02 12:32:04 +01:00
faulty.c Fix common misspellings 2011-03-31 11:26:23 -03:00
Kconfig dm: add flakey target 2011-03-24 13:54:24 +00:00
linear.c md,rcu: Convert call_rcu(free_conf) to kfree_rcu() 2011-07-20 11:05:29 -07:00
linear.h md/linear: use call_rcu to free obsolete 'conf' structures. 2009-06-18 08:49:42 +10:00
Makefile dm: add flakey target 2011-03-24 13:54:24 +00:00
md.c Merge branch 'for-linus' of git://neil.brown.name/md 2011-07-28 05:50:27 -07:00
md.h md: make it easier to wait for bad blocks to be acknowledged. 2011-07-28 11:31:48 +10:00
multipath.c md: make error_handler functions more uniform and correct. 2011-05-11 14:38:44 +10:00
multipath.h md/multipath: discard ->working_disks in favour of ->degraded 2011-05-11 14:38:02 +10:00
raid0.c block: Require subsystems to explicitly allocate bio_set integrity mempool 2011-03-17 11:11:05 +01:00
raid0.h md: fix handling of array level takeover that re-arranges devices. 2010-06-24 13:33:24 +10:00
raid1.c md/raid1: factor several functions out or raid1d() 2011-07-28 11:38:13 +10:00
raid1.h md/raid1: Handle write errors by updating badblock log. 2011-07-28 11:32:41 +10:00
raid5.c md/raid5: Clear bad blocks on successful write. 2011-07-28 11:39:23 +10:00
raid5.h md/raid5: Clear bad blocks on successful write. 2011-07-28 11:39:23 +10:00
raid10.c md/raid10: handle further errors during fix_read_error better. 2011-07-28 11:39:25 +10:00
raid10.h md/raid10: Handle write errors by updating badblock log. 2011-07-28 11:39:24 +10:00