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Message-ID: <20120210130532.GA13185@localhost>
Date: Fri, 10 Feb 2012 21:05:33 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
Jens Axboe <axboe@...nel.dk>,
Li Shaohua <shaohua.li@...el.com>,
Dave Chinner <david@...morbit.com>,
Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
Chris Mason <chris.mason@...cle.com>
Subject: [PATCH v2] block: remove plugging at buffered write time
Buffered write(2) is not directly tied to IO, so it's not suitable to
handle plug in generic_file_aio_write().
Also moves unplugging for direct I/O from around ->direct_IO() down to
do_blockdev_direct_IO().
Note that plugging for O_SYNC writes is also removed. The user may pass
arbitrary @size arguments, which may be much larger than the preferable
I/O size, or may cross extent/device boundaries. Let the lower layers
handle the plugging. The plugging code here actually turns them into
no-ops.
CC: Jens Axboe <axboe@...nel.dk>
CC: Li Shaohua <shaohua.li@...el.com>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
fs/direct-io.c | 5 +++++
fs/sync.c | 11 ++++++++++-
mm/filemap.c | 7 -------
3 files changed, 15 insertions(+), 8 deletions(-)
--- linux-next.orig/mm/filemap.c 2012-02-08 19:33:29.000000000 +0800
+++ linux-next/mm/filemap.c 2012-02-09 15:59:47.000000000 +0800
@@ -1421,12 +1421,8 @@ generic_file_aio_read(struct kiocb *iocb
retval = filemap_write_and_wait_range(mapping, pos,
pos + iov_length(iov, nr_segs) - 1);
if (!retval) {
- struct blk_plug plug;
-
- blk_start_plug(&plug);
retval = mapping->a_ops->direct_IO(READ, iocb,
iov, pos, nr_segs);
- blk_finish_plug(&plug);
}
if (retval > 0) {
*ppos = pos + retval;
@@ -2610,13 +2606,11 @@ ssize_t generic_file_aio_write(struct ki
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
- struct blk_plug plug;
ssize_t ret;
BUG_ON(iocb->ki_pos != pos);
mutex_lock(&inode->i_mutex);
- blk_start_plug(&plug);
ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
mutex_unlock(&inode->i_mutex);
@@ -2627,7 +2621,6 @@ ssize_t generic_file_aio_write(struct ki
if (err < 0 && ret > 0)
ret = err;
}
- blk_finish_plug(&plug);
return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);
--- linux-next.orig/fs/direct-io.c 2012-02-08 19:33:29.000000000 +0800
+++ linux-next/fs/direct-io.c 2012-02-09 16:03:04.000000000 +0800
@@ -1106,6 +1106,7 @@ do_blockdev_direct_IO(int rw, struct kio
unsigned long user_addr;
size_t bytes;
struct buffer_head map_bh = { 0, };
+ struct blk_plug plug;
if (rw & WRITE)
rw = WRITE_ODIRECT;
@@ -1221,6 +1222,8 @@ do_blockdev_direct_IO(int rw, struct kio
PAGE_SIZE - user_addr / PAGE_SIZE);
}
+ blk_start_plug(&plug);
+
for (seg = 0; seg < nr_segs; seg++) {
user_addr = (unsigned long)iov[seg].iov_base;
sdio.size += bytes = iov[seg].iov_len;
@@ -1279,6 +1282,8 @@ do_blockdev_direct_IO(int rw, struct kio
if (sdio.bio)
dio_bio_submit(dio, &sdio);
+ blk_finish_plug(&plug);
+
/*
* 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.
--
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