Attachment 155924 Details for Bug 242116 – [PATCH] dio: remove duplicate bio wait code

[PATCH] dio: remove duplicate bio wait code

4-dio-remove-duplicate-bio-wait-code.patch (text/x-patch), 3.35 KB, created by Jeff Moyer on 2007-06-01 19:26:52 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Jeff Moyer

Created: 2007-06-01 19:26:52 UTC

Size: 3.35 KB

patch

obsolete

>commit 20258b2b397031649e4a41922fe803d57017df84
>Author: Zach Brown <zach.brown@oracle.com>
>Date:   Sun Dec 10 02:21:01 2006 -0800
>
>    [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>
>
>diff --git a/fs/direct-io.c b/fs/direct-io.c
>index bc1cbf9..f11f05d 100644
>--- a/fs/direct-io.c
>+++ b/fs/direct-io.c
>@@ -257,7 +257,6 @@ static int dio_complete(struct dio *dio,
>  */
> 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->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 *
> 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 *b
> 	/* 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 *i
> 		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);
>

Actions: View

Attachments on bug 242116: 155921 | 155922 | 155923 | 155924 | 155925