linux-stable.git/block/elevator.c, branch linux-2.6.16.y

elevator: move clearing of unplug flag earlier

2007-04-20T22:13:30+00:00

A flag was recently added to the elevator code to avoid
performing an unplug when reuests are being re-queued.
The goal of this flag was to avoid a deep recursion that
can occur when re-queueing requests after a SCSI device/host
reset.  See http://lkml.org/lkml/2006/5/17/254

However, that fix added the flag near the bottom of a case
statement, where an earlier break (in an if statement) could
transport one out of the case, without setting the flag.
This patch sets the flag earlier in the case statement.

I re-discovered the deep recursion recently during testing;
I was told that it was a known problem, and the fix to it was
in the kernel I was testing. Indeed it was ... but it didn't
fix the bug. With the patch below, I no longer see the bug.

Signed-off by: Linas Vepstas 
Signed-off-by: Jens Axboe 
Signed-off-by: Adrian Bunk

block layer: elv_iosched_show should get elv_list_lock

2006-11-29T13:04:14+00:00

elv_iosched_show function iterates other elv_list,
hence elv_list_lock should be got.

Also the question is: in elv_iosched_show, elv_iosched_store
q->elevator->elevator_type construction is used without locking q->queue_lock.
Is it expected?..

Signed-off-by: Vasily Tarasov 
Acked-by: Jens Axboe 
Signed-off-by: Adrian Bunk

[PATCH] limit request_fn recursion

2006-05-20T22:00:31+00:00

Don't recurse back into the driver even if the unplug threshold is met,
when the driver asks for a requeue. This is both silly from a logical
point of view (requeues typically happen due to driver/hardware
shortage), and also dangerous since we could hit an endless request_fn
-> requeue -> unplug -> request_fn loop and crash on stack overrun.

Also limit blk_run_queue() to one level of recursion, similar to how
blk_start_queue() works.

This patch fixed a real problem with SLES10 and lpfc, and it could hit
any SCSI lld that returns non-zero from it's ->queuecommand() handler.

Signed-off-by: Jens Axboe 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Chris Wright

[PATCH] block: implement elv_insert and use it (fix ordcolor flipping bug)

2006-02-08T15:52:58+00:00

q->ordcolor must only be flipped on initial queueing of a hardbarrier
request.

Constructing ordered sequence and requeueing used to pass through
__elv_add_request() which flips q->ordcolor when it sees a barrier
request.

This patch separates out elv_insert() from __elv_add_request() and uses
elv_insert() when constructing ordered sequence and requeueing.
elv_insert() inserts the given request at the specified position and
does nothing else.

Signed-off-by: Tejun Heo 
Acked-by: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] block: request_queue->ordcolor must not be flipped on SOFTBARRIER

2006-02-05T19:06:51+00:00

q->ordcolor must not be flipped on SOFTBARRIER.

Signed-off-by: Tejun Heo 
Acked-by: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[BLOCK] elevator: allow default scheduler to potentially be modular

2006-01-24T09:09:14+00:00

Jens has decided that allowing the default scheduler to be a module is
a bug, and should not be allowed under kconfig.  However, I find that
scenario useful for debugging, and wish for the kernel to be able to
handle this situation without OOPSing, if I enable such an option in
the .config directly.  This patch dynamically checks for the presence
of the compiled-in default, and falls back to no-op, emitting a
suitable error message, when the default is not available

Tested for a range of boot options on 2.6.16-rc1-mm2.

Signed-off-by: Nate Diller 
Signed-off-by: Jens Axboe

[BLOCK] elevator: default choice selection

2006-01-24T09:07:58+00:00

My previous default iosched patch did a poor job dealing with the
'elevator=' boot-time option.  The old behavior falls back to the
compiled-in default if the requested one is not registered at boot
time.  This patch dynamically evaluates which default
to use, and emits a suitable error message when the requested scheduler
is not available.  It also does the 'as' -> 'anticipatory' conversion
before elevator registration, which along with a modified registration
function, allows it to correctly indicate which default scheduler is
in use.

Tested for a range of boot options on 2.6.16-rc1-mm2.

Signed-off-by: Nate Diller 
Signed-off-by: Jens Axboe

[BLOCK] elevator: if specified scheduler is not found, fall back to default

2006-01-16T08:48:58+00:00

Signed-off-by: Jens Axboe

[BLOCK] elevator: Make elevator=as work again for anticipatory

2006-01-16T08:47:37+00:00

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Jens Axboe

[PATCH] fix queue stalling while barrier sequencing

2006-01-12T17:05:39+00:00

If ordered tag isn't supported, request ordering for barrier
sequencing is performed by queue draining, which basically hangs the
request queue until elv_completed_request() reports completion of all
previous fs requests.

The condition check in elv_completed_request() was only performed for
fs requests.  If a special request is queued between the last
to-be-drained request and the barrier sequence, draining is never
completed and the queue is stalled forever.

This patch moves the end-of-draining condition check such that it's
performed for all requests.

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