linux-kernel - [PATCH] fs: direct-io: increase bio refcount as batch

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Message-Id: <1427802746-30432-1-git-send-email-ming.lei@canonical.com>
Date:	Tue, 31 Mar 2015 19:52:26 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Ming Lei <ming.lei@...onical.com>
Subject: [PATCH] fs: direct-io: increase bio refcount as batch

Each bio is always submitted to block device one by one,
so it isn't necessary to increase the bio refcount by one
each time with holding dio->bio_lock.

Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 fs/direct-io.c |   27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 6fb00e3..57b8e73 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -79,6 +79,8 @@ struct dio_submit {
 	get_block_t *get_block;		/* block mapping function */
 	dio_submit_t *submit_io;	/* IO submition function */
 
+	long	submitted_bio;
+
 	loff_t logical_offset_in_bio;	/* current first logical block in bio */
 	sector_t final_block_in_bio;	/* current final block in bio + 1 */
 	sector_t next_block_for_io;	/* next block to be put under IO,
@@ -121,7 +123,7 @@ struct dio {
 	int is_async;			/* is IO async ? */
 	bool defer_completion;		/* defer AIO completion to workqueue? */
 	int io_error;			/* IO error in completion path */
-	unsigned long refcount;		/* direct_io_worker() and bios */
+	long refcount;			/* direct_io_worker() and bios */
 	struct bio *bio_list;		/* singly linked via bi_private */
 	struct task_struct *waiter;	/* waiting task (NULL if none) */
 
@@ -383,14 +385,9 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 {
 	struct bio *bio = sdio->bio;
-	unsigned long flags;
 
 	bio->bi_private = dio;
 
-	spin_lock_irqsave(&dio->bio_lock, flags);
-	dio->refcount++;
-	spin_unlock_irqrestore(&dio->bio_lock, flags);
-
 	if (dio->is_async && dio->rw == READ)
 		bio_set_pages_dirty(bio);
 
@@ -403,15 +400,26 @@ static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 	sdio->bio = NULL;
 	sdio->boundary = 0;
 	sdio->logical_offset_in_bio = 0;
+	sdio->submitted_bio++;
 }
 
 /*
  * Release any resources in case of a failure
  */
-static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
+static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio,
+		bool commit_refcount)
 {
+	unsigned long flags;
+
 	while (sdio->head < sdio->tail)
 		page_cache_release(dio->pages[sdio->head++]);
+
+	if (!commit_refcount)
+		return;
+
+	spin_lock_irqsave(&dio->bio_lock, flags);
+	dio->refcount += (sdio->submitted_bio + 1);
+	spin_unlock_irqrestore(&dio->bio_lock, flags);
 }
 
 /*
@@ -1215,7 +1223,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	dio->i_size = i_size_read(inode);
 
 	spin_lock_init(&dio->bio_lock);
-	dio->refcount = 1;
 
 	sdio.iter = iter;
 	sdio.final_block_in_request =
@@ -1234,7 +1241,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 
 	retval = do_direct_IO(dio, &sdio, &map_bh);
 	if (retval)
-		dio_cleanup(dio, &sdio);
+		dio_cleanup(dio, &sdio, false);
 
 	if (retval == -ENOTBLK) {
 		/*
@@ -1267,7 +1274,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	 * It is possible that, we return short IO due to end of file.
 	 * In that case, we need to release all the pages we got hold on.
 	 */
-	dio_cleanup(dio, &sdio);
+	dio_cleanup(dio, &sdio, true);
 
 	/*
 	 * All block lookups have been performed. For READ requests
-- 
1.7.9.5

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