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SubjectRe: [PATCH] block: remove plugging at buffered write time
> > @@ -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);
> This one can be moved up a little bit (before dio_cleanup)

Done, thanks! Here is the updated patch with O_SYNC write fix.

Thanks,
Fengguang
---
Subject: block: remove plugging at buffered write time
Date: Tue Jan 31 18:25:48 CST 2012

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 to lower layers:
- for direct I/O, from around ->direct_IO() to do_blockdev_direct_IO()
- for O_SYNC writes, to around ->fsync()

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 | 5 +++++
fs/sync.c | 10 +++++++++-
mm/filemap.c | 7 -------
3 files changed, 14 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.
--- linux-next.orig/fs/sync.c 2012-02-09 15:59:52.000000000 +0800
+++ linux-next/fs/sync.c 2012-02-09 16:01:02.000000000 +0800
@@ -164,9 +164,17 @@ SYSCALL_DEFINE1(syncfs, int, fd)
*/
int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
{
+ struct blk_plug plug;
+ int ret;
+
if (!file->f_op || !file->f_op->fsync)
return -EINVAL;
- return file->f_op->fsync(file, start, end, datasync);
+
+ blk_start_plug(&plug);
+ ret = file->f_op->fsync(file, start, end, datasync);
+ blk_finish_plug(&plug);
+
+ return ret;
}
EXPORT_SYMBOL(vfs_fsync_range);


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