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* [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw()
@ 2019-10-14  8:26 Jan Kara
  2019-10-14  8:26 ` [PATCH 1/2] iomap: Allow forcing of waiting for running DIO " Jan Kara
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Jan Kara @ 2019-10-14  8:26 UTC (permalink / raw)
  To: linux-fsdevel
  Cc: Christoph Hellwig, darrick.wong, linux-xfs, Matthew Bobrowski,
	Dave Chinner, Jan Kara

Hello,

here is new version of the series with the small change requested by Darrick.

Changes since v2:
* Changed iomap_dio_rw() to return -EIO in case caller doesn't ask it to wait
  for sync kiocb.

Changes since v1:
* The new function argument of iomap_dio_rw() does not get overridden by
 is_sync_kiocb() the caller is responsible for this.

---
Original motivation:

when doing the ext4 conversion of direct IO code to iomap, we found it very
difficult to handle inode extension with what iomap code currently provides.
Ext4 wants to do inode extension as sync IO (so that the whole duration of
IO is protected by inode->i_rwsem), also we need to truncate blocks beyond
end of file in case of error or short write. Now in ->end_io handler we don't
have the information how long originally the write was (to judge whether we
may have allocated more blocks than we actually used) and in ->write_iter
we don't know whether / how much of the IO actually succeeded in case of AIO.

Thinking about it for some time I think iomap code makes it unnecessarily
complex for the filesystem in case it decides it doesn't want to perform AIO
and wants to fall back to good old synchronous IO. In such case it is much
easier for the filesystem if it just gets normal error return from
iomap_dio_rw() and not just -EIOCBQUEUED.

The first patch in the series adds argument to iomap_dio_rw() to wait for IO
completion (internally iomap_dio_rw() already supports this!) and the second
patch converts XFS waiting for unaligned DIO write to this new API.

								Honza 

Previous versions:
Link: http://lore.kernel.org/r/20191009202736.19227-1-jack@suse.cz
Link: http://lore.kernel.org/r/20191011125520.11697-1-jack@suse.cz

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH 1/2] iomap: Allow forcing of waiting for running DIO in iomap_dio_rw()
  2019-10-14  8:26 [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Jan Kara
@ 2019-10-14  8:26 ` Jan Kara
  2019-10-14  8:40   ` Christoph Hellwig
  2019-10-14  8:26 ` [PATCH 2/2] xfs: Use iomap_dio_rw_wait() Jan Kara
  2019-10-14  8:52 ` [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Matthew Bobrowski
  2 siblings, 1 reply; 7+ messages in thread
From: Jan Kara @ 2019-10-14  8:26 UTC (permalink / raw)
  To: linux-fsdevel
  Cc: Christoph Hellwig, darrick.wong, linux-xfs, Matthew Bobrowski,
	Dave Chinner, Jan Kara

Filesystems do not support doing IO as asynchronous in some cases. For
example in case of unaligned writes or in case file size needs to be
extended (e.g. for ext4). Instead of forcing filesystem to wait for AIO
in such cases, add argument to iomap_dio_rw() which makes the function
wait for IO completion. This also results in executing
iomap_dio_complete() inline in iomap_dio_rw() providing its return value
to the caller as for ordinary sync IO.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/gfs2/file.c        | 6 ++++--
 fs/iomap/direct-io.c  | 7 +++++--
 fs/xfs/xfs_file.c     | 5 +++--
 include/linux/iomap.h | 3 ++-
 4 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 997b326247e2..f0caee2b7c00 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -732,7 +732,8 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to)
 	if (ret)
 		goto out_uninit;
 
-	ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL);
+	ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL,
+			   is_sync_kiocb(iocb));
 
 	gfs2_glock_dq(&gh);
 out_uninit:
@@ -767,7 +768,8 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	if (offset + len > i_size_read(&ip->i_inode))
 		goto out;
 
-	ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL);
+	ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL,
+			   is_sync_kiocb(iocb));
 
 out:
 	gfs2_glock_dq(&gh);
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 1fc28c2da279..da124cee1783 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -392,7 +392,8 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
  */
 ssize_t
 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
-		const struct iomap_ops *ops, const struct iomap_dio_ops *dops)
+		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
+		bool wait_for_completion)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
 	struct inode *inode = file_inode(iocb->ki_filp);
@@ -400,7 +401,6 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 	loff_t pos = iocb->ki_pos, start = pos;
 	loff_t end = iocb->ki_pos + count - 1, ret = 0;
 	unsigned int flags = IOMAP_DIRECT;
-	bool wait_for_completion = is_sync_kiocb(iocb);
 	struct blk_plug plug;
 	struct iomap_dio *dio;
 
@@ -409,6 +409,9 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 	if (!count)
 		return 0;
 
+	if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))
+		return -EIO;
+
 	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
 	if (!dio)
 		return -ENOMEM;
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 1ffb179f35d2..0739ba72a82e 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -188,7 +188,7 @@ xfs_file_dio_aio_read(
 	file_accessed(iocb->ki_filp);
 
 	xfs_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dio_rw(iocb, to, &xfs_iomap_ops, NULL);
+	ret = iomap_dio_rw(iocb, to, &xfs_iomap_ops, NULL, is_sync_kiocb(iocb));
 	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	return ret;
@@ -547,7 +547,8 @@ xfs_file_dio_aio_write(
 	}
 
 	trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
-	ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops);
+	ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops,
+			   is_sync_kiocb(iocb));
 
 	/*
 	 * If unaligned, this is the only IO in-flight. If it has not yet
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 7aa5d6117936..76b14cb729dc 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -195,7 +195,8 @@ struct iomap_dio_ops {
 };
 
 ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
-		const struct iomap_ops *ops, const struct iomap_dio_ops *dops);
+		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
+		bool wait_for_completion);
 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
 
 #ifdef CONFIG_SWAP
-- 
2.16.4


^ permalink raw reply related	[flat|nested] 7+ messages in thread

* [PATCH 2/2] xfs: Use iomap_dio_rw_wait()
  2019-10-14  8:26 [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Jan Kara
  2019-10-14  8:26 ` [PATCH 1/2] iomap: Allow forcing of waiting for running DIO " Jan Kara
@ 2019-10-14  8:26 ` Jan Kara
  2019-10-14  8:41   ` Christoph Hellwig
  2019-10-14  8:52 ` [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Matthew Bobrowski
  2 siblings, 1 reply; 7+ messages in thread
From: Jan Kara @ 2019-10-14  8:26 UTC (permalink / raw)
  To: linux-fsdevel
  Cc: Christoph Hellwig, darrick.wong, linux-xfs, Matthew Bobrowski,
	Dave Chinner, Jan Kara

Use iomap_dio_rw() to wait for unaligned direct IO instead of opencoding
the wait.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_file.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 0739ba72a82e..c0620135a279 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -547,16 +547,12 @@ xfs_file_dio_aio_write(
 	}
 
 	trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
-	ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops,
-			   is_sync_kiocb(iocb));
-
 	/*
-	 * If unaligned, this is the only IO in-flight. If it has not yet
-	 * completed, wait on it before we release the iolock to prevent
-	 * subsequent overlapping IO.
+	 * If unaligned, this is the only IO in-flight. Wait on it before we
+	 * release the iolock to prevent subsequent overlapping IO.
 	 */
-	if (ret == -EIOCBQUEUED && unaligned_io)
-		inode_dio_wait(inode);
+	ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops,
+			   is_sync_kiocb(iocb) || unaligned_io);
 out:
 	xfs_iunlock(ip, iolock);
 
-- 
2.16.4


^ permalink raw reply related	[flat|nested] 7+ messages in thread

* Re: [PATCH 1/2] iomap: Allow forcing of waiting for running DIO in iomap_dio_rw()
  2019-10-14  8:26 ` [PATCH 1/2] iomap: Allow forcing of waiting for running DIO " Jan Kara
@ 2019-10-14  8:40   ` Christoph Hellwig
  0 siblings, 0 replies; 7+ messages in thread
From: Christoph Hellwig @ 2019-10-14  8:40 UTC (permalink / raw)
  To: Jan Kara
  Cc: linux-fsdevel, Christoph Hellwig, darrick.wong, linux-xfs,
	Matthew Bobrowski, Dave Chinner

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] xfs: Use iomap_dio_rw_wait()
  2019-10-14  8:26 ` [PATCH 2/2] xfs: Use iomap_dio_rw_wait() Jan Kara
@ 2019-10-14  8:41   ` Christoph Hellwig
  0 siblings, 0 replies; 7+ messages in thread
From: Christoph Hellwig @ 2019-10-14  8:41 UTC (permalink / raw)
  To: Jan Kara
  Cc: linux-fsdevel, Christoph Hellwig, darrick.wong, linux-xfs,
	Matthew Bobrowski, Dave Chinner

On Mon, Oct 14, 2019 at 10:26:03AM +0200, Jan Kara wrote:
> Use iomap_dio_rw() to wait for unaligned direct IO instead of opencoding
> the wait.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw()
  2019-10-14  8:26 [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Jan Kara
  2019-10-14  8:26 ` [PATCH 1/2] iomap: Allow forcing of waiting for running DIO " Jan Kara
  2019-10-14  8:26 ` [PATCH 2/2] xfs: Use iomap_dio_rw_wait() Jan Kara
@ 2019-10-14  8:52 ` Matthew Bobrowski
  2019-10-14  9:32   ` Jan Kara
  2 siblings, 1 reply; 7+ messages in thread
From: Matthew Bobrowski @ 2019-10-14  8:52 UTC (permalink / raw)
  To: Jan Kara
  Cc: linux-fsdevel, Christoph Hellwig, darrick.wong, linux-xfs, Dave Chinner

On Mon, Oct 14, 2019 at 10:26:01AM +0200, Jan Kara wrote:
> Original motivation:
> 
> when doing the ext4 conversion of direct IO code to iomap, we found it very
> difficult to handle inode extension with what iomap code currently provides.
> Ext4 wants to do inode extension as sync IO (so that the whole duration of
> IO is protected by inode->i_rwsem), also we need to truncate blocks beyond
> end of file in case of error or short write. Now in ->end_io handler we don't
> have the information how long originally the write was (to judge whether we
> may have allocated more blocks than we actually used) and in ->write_iter
> we don't know whether / how much of the IO actually succeeded in case of AIO.
> 
> Thinking about it for some time I think iomap code makes it unnecessarily
> complex for the filesystem in case it decides it doesn't want to perform AIO
> and wants to fall back to good old synchronous IO. In such case it is much
> easier for the filesystem if it just gets normal error return from
> iomap_dio_rw() and not just -EIOCBQUEUED.
> 
> The first patch in the series adds argument to iomap_dio_rw() to wait for IO
> completion (internally iomap_dio_rw() already supports this!) and the second
> patch converts XFS waiting for unaligned DIO write to this new API.

Ah, wonderful, I was waiting for this to come through.

I'll rebase my EXT4 direct I/O port on top of these patches and apply
the discussed changes. Any objections? :)

--<M>--

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw()
  2019-10-14  8:52 ` [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Matthew Bobrowski
@ 2019-10-14  9:32   ` Jan Kara
  0 siblings, 0 replies; 7+ messages in thread
From: Jan Kara @ 2019-10-14  9:32 UTC (permalink / raw)
  To: Matthew Bobrowski
  Cc: Jan Kara, linux-fsdevel, Christoph Hellwig, darrick.wong,
	linux-xfs, Dave Chinner

On Mon 14-10-19 19:52:18, Matthew Bobrowski wrote:
> On Mon, Oct 14, 2019 at 10:26:01AM +0200, Jan Kara wrote:
> > Original motivation:
> > 
> > when doing the ext4 conversion of direct IO code to iomap, we found it very
> > difficult to handle inode extension with what iomap code currently provides.
> > Ext4 wants to do inode extension as sync IO (so that the whole duration of
> > IO is protected by inode->i_rwsem), also we need to truncate blocks beyond
> > end of file in case of error or short write. Now in ->end_io handler we don't
> > have the information how long originally the write was (to judge whether we
> > may have allocated more blocks than we actually used) and in ->write_iter
> > we don't know whether / how much of the IO actually succeeded in case of AIO.
> > 
> > Thinking about it for some time I think iomap code makes it unnecessarily
> > complex for the filesystem in case it decides it doesn't want to perform AIO
> > and wants to fall back to good old synchronous IO. In such case it is much
> > easier for the filesystem if it just gets normal error return from
> > iomap_dio_rw() and not just -EIOCBQUEUED.
> > 
> > The first patch in the series adds argument to iomap_dio_rw() to wait for IO
> > completion (internally iomap_dio_rw() already supports this!) and the second
> > patch converts XFS waiting for unaligned DIO write to this new API.
> 
> Ah, wonderful, I was waiting for this to come through.
> 
> I'll rebase my EXT4 direct I/O port on top of these patches and apply
> the discussed changes. Any objections? :)

No, go ahead. Thanks!

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2019-10-14  9:32 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-14  8:26 [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Jan Kara
2019-10-14  8:26 ` [PATCH 1/2] iomap: Allow forcing of waiting for running DIO " Jan Kara
2019-10-14  8:40   ` Christoph Hellwig
2019-10-14  8:26 ` [PATCH 2/2] xfs: Use iomap_dio_rw_wait() Jan Kara
2019-10-14  8:41   ` Christoph Hellwig
2019-10-14  8:52 ` [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw() Matthew Bobrowski
2019-10-14  9:32   ` Jan Kara

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