linux-kernel - [patch v4 1/2] block: get rid of the WRITE

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Date:	Fri, 02 Oct 2009 18:56:53 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	zach.brown@...cle.com
Cc:	linux-aio <linux-aio@...ck.org>,
	Linux Kernel Mailing <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: [patch v4 1/2] block: get rid of the WRITE_ODIRECT flag

Hi,

The WRITE_ODIRECT flag is only used in one place, and that code path
happens to also call blk_run_address_space.  The introduction of this
flag, then, could result in the device being unplugged twice for every
I/O.

Further, with the batching changes in the next patch, we don't want an
O_DIRECT write to imply a queue unplug.

Signed-off-by: Jeff Moyer <jmoyer@...hat.com>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 8b10b87..c86d35f 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1124,7 +1124,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	int acquire_i_mutex = 0;
 
 	if (rw & WRITE)
-		rw = WRITE_ODIRECT;
+		rw = WRITE_SYNC_PLUG;
 
 	if (bdev)
 		bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2adaa25..2aac751 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -129,7 +129,6 @@ struct inodes_stat_t {
  * WRITE_SYNC		Like WRITE_SYNC_PLUG, but also unplugs the device
  *			immediately after submission. The write equivalent
  *			of READ_SYNC.
- * WRITE_ODIRECT	Special case write for O_DIRECT only.
  * SWRITE_SYNC
  * SWRITE_SYNC_PLUG	Like WRITE_SYNC/WRITE_SYNC_PLUG, but locks the buffer.
  *			See SWRITE.
@@ -151,7 +150,6 @@ struct inodes_stat_t {
 #define READ_META	(READ | (1 << BIO_RW_META))
 #define WRITE_SYNC_PLUG	(WRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_NOIDLE))
 #define WRITE_SYNC	(WRITE_SYNC_PLUG | (1 << BIO_RW_UNPLUG))
-#define WRITE_ODIRECT	(WRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
 #define SWRITE_SYNC_PLUG	\
 			(SWRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_NOIDLE))
 #define SWRITE_SYNC	(SWRITE_SYNC_PLUG | (1 << BIO_RW_UNPLUG))
--
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