linux.git/block/elevator.c, branch v2.6.29

block: get rid of elevator_t typedef

2008-12-29T07:29:50+00:00

Just use struct elevator_queue everywhere instead.

Signed-off-by: Jens Axboe

block: simplify empty barrier implementation

2008-12-29T07:28:45+00:00

Empty barrier required special handling in __elv_next_request() to
complete it without letting the low level driver see it.

With previous changes, barrier code is now flexible enough to skip the
BAR step using the same barrier sequence selection mechanism.  Drop
the special handling and mask off q->ordered from start_ordered().

Remove blk_empty_barrier() test which now has no user.

Signed-off-by: Tejun Heo 
Signed-off-by: Jens Axboe

block: make barrier completion more robust

2008-12-29T07:28:45+00:00

Barrier completion had the following assumptions.

* start_ordered() couldn't finish the whole sequence properly.  If all
  actions are to be skipped, q->ordseq is set correctly but the actual
  completion was never triggered thus hanging the barrier request.

* Drain completion in elv_complete_request() assumed that there's
  always at least one request in the queue when drain completes.

Both assumptions are true but these assumptions need to be removed to
improve empty barrier implementation.  This patch makes the following
changes.

* Make start_ordered() use blk_ordered_complete_seq() to mark skipped
  steps complete and notify __elv_next_request() that it should fetch
  the next request if the whole barrier has completed inside
  start_ordered().

* Make drain completion path in elv_complete_request() check whether
  the queue is empty.  Empty queue also indicates drain completion.

* While at it, convert 0/1 return from blk_do_ordered() to false/true.

Signed-off-by: Tejun Heo 
Signed-off-by: Jens Axboe

Merge branches 'tracing/ftrace', 'tracing/function-graph-tracer' and 'tracing/urgent' into tracing/core

2008-12-05T13:45:22+00:00

block: internal dequeue shouldn't start timer

2008-12-03T11:41:26+00:00

blkdev_dequeue_request() and elv_dequeue_request() are equivalent and
both start the timeout timer.  Barrier code dequeues the original
barrier request but doesn't passes the request itself to lower level
driver, only broken down proxy requests; however, as the original
barrier code goes through the same dequeue path and timeout timer is
started on it.  If barrier sequence takes long enough, this timer
expires but the low level driver has no idea about this request and
oops follows.

Timeout timer shouldn't have been started on the original barrier
request as it never goes through actual IO.  This patch unexports
elv_dequeue_request(), which has no external user anyway, and makes it
operate on elevator proper w/o adding the timer and make
blkdev_dequeue_request() call elv_dequeue_request() and add timer.
Internal users which don't pass the request to driver - barrier code
and end_that_request_last() - are converted to use
elv_dequeue_request().

Signed-off-by: Tejun Heo 
Cc: Mike Anderson 
Signed-off-by: Jens Axboe

blktrace: port to tracepoints, update

2008-11-26T12:04:35+00:00

Port to the new tracepoints API: split DEFINE_TRACE() and DECLARE_TRACE()
sites. Spread them out to the usage sites, as suggested by
Mathieu Desnoyers.

Signed-off-by: Ingo Molnar 
Acked-by: Mathieu Desnoyers

blktrace: port to tracepoints

2008-11-26T11:13:34+00:00

This was a forward port of work done by Mathieu Desnoyers, I changed it to
encode the 'what' parameter on the tracepoint name, so that one can register
interest in specific events and not on classes of events to then check the
'what' parameter.

Signed-off-by: Arnaldo Carvalho de Melo 
Signed-off-by: Jens Axboe 
Signed-off-by: Ingo Molnar

block: add timer on blkdev_dequeue_request() not elv_next_request()

2008-11-06T07:41:55+00:00

Block queue supports two usage models - one where block driver peeks
at the front of queue using elv_next_request(), processes it and
finishes it and the other where block driver peeks at the front of
queue, dequeue the request using blkdev_dequeue_request() and finishes
it.  The latter is more flexible as it allows the driver to process
multiple commands concurrently.

These two inconsistent usage models affect the block layer
implementation confusing.  For some, elv_next_request() is considered
the issue point while others consider blkdev_dequeue_request() the
issue point.

Till now the inconsistency mostly affect only accounting, so it didn't
really break anything seriously; however, with block layer timeout,
this inconsistency hits hard.  Block layer considers
elv_next_request() the issue point and adds timer but SCSI layer
thinks it was just peeking and when the request can't process the
command right away, it's just left there without further processing.
This makes the request dangling on the timer list and, when the timer
goes off, the request which the SCSI layer and below think is still on
the block queue ends up in the EH queue, causing various problems - EH
hang (failed count goes over busy count and EH never wakes up),
WARN_ON() and oopses as low level driver trying to handle the unknown
command, etc. depending on the timing.

As SCSI midlayer is the only user of block layer timer at the moment,
moving blk_add_timer() to elv_dequeue_request() fixes the problem;
however, this two usage models definitely need to be cleaned up in the
future.

Signed-off-by: Tejun Heo 
Signed-off-by: Jens Axboe

block: only call ->request_fn when the queue is not stopped

2008-10-17T06:46:57+00:00

Callers should use either blk_run_queue/__blk_run_queue, or
blk_start_queueing() to invoke request handling instead of calling
->request_fn() directly as that does not take the queue stopped
flag into account.

Also add appropriate comments on the above functions to detail
their usage.

Signed-off-by: Jens Axboe

block: simplify string handling in elv_iosched_store()

2008-10-17T06:46:57+00:00

strlcpy() guarantees the dest buffer is NULL teminated.

Signed-off-by: Li Zefan 
Signed-off-by: Jens Axboe