linux-toradex.git/include/linux/raid/raid5.h, branch v2.6.23.14

md: handle_stripe5 - add request/completion logic for async read ops

2007-07-13T15:06:17+00:00

When a read bio is attached to the stripe and the corresponding block is
marked R5_UPTODATE, then a read (biofill) operation is scheduled to copy
the data from the stripe cache to the bio buffer.  handle_stripe flags the
blocks to be operated on with the R5_Wantfill flag.  If new read requests
arrive while raid5_run_ops is running they will not be handled until
handle_stripe is scheduled to run again.

Changelog:
* cleanup to_read and to_fill accounting
* do not fail reads that have reached the cache

Signed-off-by: Dan Williams 
Acked-By: NeilBrown

md: handle_stripe5 - add request/completion logic for async compute ops

2007-07-13T15:06:17+00:00

handle_stripe will compute a block when a backing disk has failed, or when
it determines it can save a disk read by computing the block from all the
other up-to-date blocks.

Previously a block would be computed under the lock and subsequent logic in
handle_stripe could use the newly up-to-date block.  With the raid5_run_ops
implementation the compute operation is carried out a later time outside
the lock.  To preserve the old functionality we take advantage of the
dependency chain feature of async_tx to flag the block as R5_Wantcompute
and then let other parts of handle_stripe operate on the block as if it
were up-to-date.  raid5_run_ops guarantees that the block will be ready
before it is used in another operation.

However, this only works in cases where the compute and the dependent
operation are scheduled at the same time.  If a previous call to
handle_stripe sets the R5_Wantcompute flag there is no facility to pass the
async_tx dependency chain across successive calls to raid5_run_ops.  The
req_compute variable protects against this case.

Changelog:
* remove the req_compute BUG_ON

Signed-off-by: Dan Williams 
Acked-By: NeilBrown

md: raid5_run_ops - run stripe operations outside sh->lock

2007-07-13T15:06:15+00:00

When the raid acceleration work was proposed, Neil laid out the following
attack plan:

1/ move the xor and copy operations outside spin_lock(&sh->lock)
2/ find/implement an asynchronous offload api

The raid5_run_ops routine uses the asynchronous offload api (async_tx) and
the stripe_operations member of a stripe_head to carry out xor+copy
operations asynchronously, outside the lock.

To perform operations outside the lock a new set of state flags is needed
to track new requests, in-flight requests, and completed requests.  In this
new model handle_stripe is tasked with scanning the stripe_head for work,
updating the stripe_operations structure, and finally dropping the lock and
calling raid5_run_ops for processing.  The following flags outline the
requests that handle_stripe can make of raid5_run_ops:

STRIPE_OP_BIOFILL
 - copy data into request buffers to satisfy a read request
STRIPE_OP_COMPUTE_BLK
 - generate a missing block in the cache from the other blocks
STRIPE_OP_PREXOR
 - subtract existing data as part of the read-modify-write process
STRIPE_OP_BIODRAIN
 - copy data out of request buffers to satisfy a write request
STRIPE_OP_POSTXOR
 - recalculate parity for new data that has entered the cache
STRIPE_OP_CHECK
 - verify that the parity is correct
STRIPE_OP_IO
 - submit i/o to the member disks (note this was already performed outside
   the stripe lock, but it made sense to add it as an operation type

The flow is:
1/ handle_stripe sets STRIPE_OP_* in sh->ops.pending
2/ raid5_run_ops reads sh->ops.pending, sets sh->ops.ack, and submits the
   operation to the async_tx api
3/ async_tx triggers the completion callback routine to set
   sh->ops.complete and release the stripe
4/ handle_stripe runs again to finish the operation and optionally submit
   new operations that were previously blocked

Note this patch just defines raid5_run_ops, subsequent commits (one per
major operation type) modify handle_stripe to take advantage of this
routine.

Changelog:
* removed ops_complete_biodrain in favor of ops_complete_postxor and
  ops_complete_write.
* removed the raid5_run_ops workqueue
* call bi_end_io for reads in ops_complete_biofill, saves a call to
  handle_stripe
* explicitly handle the 2-disk raid5 case (xor becomes memcpy), Neil Brown
* fix race between async engines and bi_end_io call for reads, Neil Brown
* remove unnecessary spin_lock from ops_complete_biofill
* remove test_and_set/test_and_clear BUG_ONs, Neil Brown
* remove explicit interrupt handling for channel switching, this feature
  was absorbed (i.e. it is now implicit) by the async_tx api
* use return_io in ops_complete_biofill

Signed-off-by: Dan Williams 
Acked-By: NeilBrown

raid5: refactor handle_stripe5 and handle_stripe6 (v3)

2007-07-13T15:06:15+00:00

handle_stripe5 and handle_stripe6 have very deep logic paths handling the
various states of a stripe_head.  By introducing the 'stripe_head_state'
and 'r6_state' objects, large portions of the logic can be moved to
sub-routines.

'struct stripe_head_state' consumes all of the automatic variables that previously
stood alone in handle_stripe5,6.  'struct r6_state' contains the handle_stripe6
specific variables like p_failed and q_failed.

One of the nice side effects of the 'stripe_head_state' change is that it
allows for further reductions in code duplication between raid5 and raid6.
The following new routines are shared between raid5 and raid6:

	handle_completed_write_requests
	handle_requests_to_failed_array
	handle_stripe_expansion

Changes:
* v2: fixed 'conf->raid_disk-1' for the raid6 'handle_stripe_expansion' path
* v3: removed the unused 'dirty' field from struct stripe_head_state
* v3: coalesced open coded bi_end_io routines into return_io()

Signed-off-by: Dan Williams 
Acked-By: NeilBrown

[PATCH] md: allow reads that have bypassed the cache to be retried on failure

2006-12-10T17:57:20+00:00

If a bypass-the-cache read fails, we simply try again through the cache.  If
it fails again it will trigger normal recovery precedures.

update 1:

From: NeilBrown 

1/
  chunk_aligned_read and retry_aligned_read assume that
      data_disks == raid_disks - 1
  which is not true for raid6.
  So when an aligned read request bypasses the cache, we can get the wrong data.

2/ The cloned bio is being used-after-free in raid5_align_endio
   (to test BIO_UPTODATE).

3/ We forgot to add rdev->data_offset when submitting
   a bio for aligned-read

4/ clone_bio calls blk_recount_segments and then we change bi_bdev,
   so we need to invalidate the segment counts.

5/ We don't de-reference the rdev when the read completes.
   This means we need to record the rdev to so it is still
   available in the end_io routine.  Fortunately
   bi_next in the original bio is unused at this point so
   we can stuff it in there.

6/ We leak a cloned bio if the target rdev is not usable.

From: NeilBrown 

update 2:

1/ When aligned requests fail (read error) they need to be retried
   via the normal method (stripe cache).  As we cannot be sure that
   we can process a single read in one go (we may not be able to
   allocate all the stripes needed) we store a bio-being-retried
   and a list of bioes-that-still-need-to-be-retried.
   When find a bio that needs to be retried, we should add it to
   the list, not to single-bio...

2/ We were never incrementing 'scnt' when resubmitting failed
   aligned requests.

[akpm@osdl.org: build fix]
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] slab: remove kmem_cache_t

2006-12-07T16:39:25+00:00

Replace all uses of kmem_cache_t with struct kmem_cache.

The patch was generated using the following script:

	#!/bin/sh
	#
	# Replace one string by another in all the kernel sources.
	#

	set -e

	for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do
		quilt add $file
		sed -e "1,\$s/$1/$2/g" $file >/tmp/$$
		mv /tmp/$$ $file
		quilt refresh
	done

The script was run like this

	sh replace kmem_cache_t "struct kmem_cache"

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] md: remove the working_disks and failed_disks from raid5 state data.

2006-10-03T15:04:17+00:00

They are not needed.  conf->failed_disks is the same as mddev->degraded and
conf->working_disks is conf->raid_disks - mddev->degraded.

Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] md: fix a comment that is wrong in raid5.h

2006-10-03T15:04:16+00:00

Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] md: merge raid5 and raid6 code

2006-06-26T16:58:37+00:00

There is a lot of commonality between raid5.c and raid6main.c.  This patches
merges both into one module called raid456.  This saves a lot of code, and
paves the way for online raid5->raid6 migrations.

There is still duplication, e.g.  between handle_stripe5 and handle_stripe6.
This will probably be cleaned up later.

Cc: "H. Peter Anvin" 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] md: Only checkpoint expansion progress occasionally

2006-03-27T16:45:02+00:00

Instead of checkpointing at each stripe, only checkpoint when a new write
would overwrite uncheckpointed data.  Block any write to the uncheckpointed
area.  Arbitrarily checkpoint at least every 3Meg.

Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds