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[PATCH] dio: remove duplicate bio wait code 

Now that we have a single refcount and waiting path we can reuse it in the
async 'should_wait' path.  It continues to rely on the fragile link between
the conditional in dio_complete_aio() which decides to complete the AIO and
the conditional in direct_io_worker() which decides to wait and free.

By waiting before dropping the reference we stop dio_bio_end_aio() from
calling dio_complete_aio() which used to wake up the waiter after seeing the
reference count drop to 0.  We hoist this wake up into dio_bio_end_aio() which
now notices when it's left a single remaining reference that is held by the
waiter.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Zach Brown 2006-12-10 02:21:01 -08:00 committed by Linus Torvalds
parent 0273201e69
commit 20258b2b39
1 changed files with 12 additions and 29 deletions
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41
fs/direct-io.c
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@ -257,7 +257,6 @@ static int dio_complete(struct dio *dio, loff_t offset, int ret)
*/
static void dio_complete_aio(struct dio *dio)
{
unsigned long flags;
int ret;
ret = dio_complete(dio, dio->iocb->ki_pos, 0);
@ -267,14 +266,6 @@ static void dio_complete_aio(struct dio *dio)
((dio->rw == READ) && dio->result)) {
aio_complete(dio->iocb, ret, 0);
kfree(dio);
} else {
/*
* Falling back to buffered
*/
spin_lock_irqsave(&dio->bio_lock, flags);
if (dio->waiter)
wake_up_process(dio->waiter);
spin_unlock_irqrestore(&dio->bio_lock, flags);
}
}
@ -285,6 +276,8 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio);
static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
{
struct dio *dio = bio->bi_private;
int waiter_holds_ref = 0;
int remaining;
if (bio->bi_size)
return 1;
@ -292,7 +285,12 @@ static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
/* cleanup the bio */
dio_bio_complete(dio, bio);
if (atomic_dec_and_test(&dio->refcount))
waiter_holds_ref = !!dio->waiter;
remaining = atomic_sub_return(1, (&dio->refcount));
if (remaining == 1 && waiter_holds_ref)
wake_up_process(dio->waiter);
if (remaining == 0)
dio_complete_aio(dio);
return 0;
@ -1097,30 +1095,15 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
if (ret == 0)
ret = dio->result;
if (should_wait)
dio_await_completion(dio);
/* this can free the dio */
if (atomic_dec_and_test(&dio->refcount))
dio_complete_aio(dio);
if (should_wait) {
unsigned long flags;
/*
* Wait for already issued I/O to drain out and
* release its references to user-space pages
* before returning to fallback on buffered I/O
*/
spin_lock_irqsave(&dio->bio_lock, flags);
set_current_state(TASK_UNINTERRUPTIBLE);
while (atomic_read(&dio->refcount)) {
spin_unlock_irqrestore(&dio->bio_lock, flags);
io_schedule();
spin_lock_irqsave(&dio->bio_lock, flags);
set_current_state(TASK_UNINTERRUPTIBLE);
}
spin_unlock_irqrestore(&dio->bio_lock, flags);
set_current_state(TASK_RUNNING);
if (should_wait)
kfree(dio);
}
} else {
dio_await_completion(dio);