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dm: remove dm_request loop 

Remove queue_io return value and a loop in dm_request.

IO may be submitted to a worker thread with queue_io().  queue_io() sets
DMF_QUEUE_IO_TO_THREAD so that all further IO is queued for the thread. When
the thread finishes its work, it clears DMF_QUEUE_IO_TO_THREAD and from this
point on, requests are submitted from dm_request again. This will be used
for processing barriers.

Remove the loop in dm_request. queue_io() can submit I/Os to the worker thread
even if DMF_QUEUE_IO_TO_THREAD was not set.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2009-04-09 00:27:15 +01:00 committed by Alasdair G Kergon
parent 3b00b2036f
commit 92c639021c
1 changed files with 7 additions and 15 deletions
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22
drivers/md/dm.c
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@ -436,21 +436,18 @@ static void end_io_acct(struct dm_io *io)
/*
* Add the bio to the list of deferred io.
*/
static int queue_io(struct mapped_device *md, struct bio *bio)
static void queue_io(struct mapped_device *md, struct bio *bio)
{
down_write(&md->io_lock);
if (!test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) {
up_write(&md->io_lock);
return 1;
}
spin_lock_irq(&md->deferred_lock);
bio_list_add(&md->deferred, bio);
spin_unlock_irq(&md->deferred_lock);
if (!test_and_set_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags))
queue_work(md->wq, &md->work);
up_write(&md->io_lock);
return 0; /* deferred successfully */
}
/*
@ -953,7 +950,7 @@ static int dm_request(struct request_queue *q, struct bio *bio)
* If we're suspended or the thread is processing barriers
* we have to queue this io for later.
*/
while (test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) {
if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags))) {
up_read(&md->io_lock);
if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) &&
@ -962,14 +959,9 @@ static int dm_request(struct request_queue *q, struct bio *bio)
return 0;
}
if (!queue_io(md, bio))
return 0;
queue_io(md, bio);
/*
* We're in a while loop, because someone could suspend
* before we get to the following read lock.
*/
down_read(&md->io_lock);
return 0;
}
__split_and_process_bio(md, bio);