kernel/linux.git/block/elevator.c, branch linux-2.6.28.y

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

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

block: change elevator to use __blk_end_request()

2008-10-09T06:56:21+00:00

This patch converts elevator to use __blk_end_request() directly so that end_{queued|dequeued}_request() can be removed. Related 'uptodate' arguments is converted to 'error'. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Signed-off-by: Jens Axboe

block: Add interface to abort queued requests

2008-10-09T06:56:13+00:00

Signed-off-by: Mike Anderson Signed-off-by: Jens Axboe

block: unify request timeout handling

2008-10-09T06:56:13+00:00

Right now SCSI and others do their own command timeout handling. Move those bits to the block layer. Instead of having a timer per command, we try to be a bit more clever and simply have one per-queue. This avoids the overhead of having to tear down and setup a timer for each command, so it will result in a lot less timer fiddling. Signed-off-by: Mike Anderson Signed-off-by: Jens Axboe

block: use linux/uaccess.h in elevator.c instead of asm variant

2008-10-09T06:56:09+00:00

Signed-off-by: Jens Axboe

drop vmerge accounting

2008-10-09T06:56:03+00:00

Remove hw_segments field from struct bio and struct request. Without virtual merge accounting they have no purpose. Signed-off-by: Mikulas Patocka Signed-off-by: Jens Axboe

Allow elevators to sort/merge discard requests

2008-10-09T06:56:02+00:00

But blkdev_issue_discard() still emits requests which are interpreted as soft barriers, because naïve callers might otherwise issue subsequent writes to those same sectors, which might cross on the queue (if they're reallocated quickly enough). Callers still _can_ issue non-barrier discard requests, but they have to take care of queue ordering for themselves. Signed-off-by: David Woodhouse Signed-off-by: Jens Axboe