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Subject[PATCH] 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 remove the redundant plug calls around ->direct_IO(), since we now
do unplugging in the lower layer do_blockdev_direct_IO().

CC: Jens Axboe <axboe@kernel.dk>
CC: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
fs/direct-io.c | 4 ++++
mm/filemap.c | 7 -------
2 files changed, 4 insertions(+), 7 deletions(-)

--- linux-next.orig/mm/filemap.c 2012-02-08 18:51:50.000000000 +0800
+++ linux-next/mm/filemap.c 2012-02-08 18:52:19.000000000 +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 18:51:37.000000000 +0800
+++ linux-next/fs/direct-io.c 2012-02-08 18:52:19.000000000 +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;
@@ -1314,6 +1317,7 @@ do_blockdev_direct_IO(int rw, struct kio
} else
BUG_ON(retval != -EIOCBQUEUED);

+ blk_finish_plug(&plug);
out:
return retval;
}

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