[2/3] iomap: iomap_dio_rw() handles all sync writes

Commit Message

Dave Chinner March 27, 2018, 7:07 a.m. UTC

From: Dave Chinner <[e-mail]>

Currently iomap_dio_rw() only handles (data)sync write completions
for AIO. This means we can't optimised non-AIO IO to minimise device
flushes as we can't tell the caller whether a flush is required or
not.

To solve this problem and enable further optimisations, make
iomap_dio_rw responsible for data sync behaviour for all IO, not
just AIO.

In doing so, the sync operation is now accounted as part of the DIO
IO by inode_dio_end(), hence post-IO data stability updates will no
long race against operations that serialise via inode_dio_wait()
such as truncate or hole punch.

Signed-Off-By: Dave Chinner <[e-mail]>
---
 fs/iomap.c        | 17 ++++++++++++++---
 fs/xfs/xfs_file.c |  5 -----
 2 files changed, 14 insertions(+), 8 deletions(-)

Comments

Christoph Hellwig March 28, 2018, 7:38 a.m. UTC | #1

> @@ -769,12 +777,9 @@ static void iomap_dio_complete_work(struct work_struct *work)
>  {
>  	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
>  	struct kiocb *iocb = dio->iocb;
> -	bool is_write = (dio->flags & IOMAP_DIO_WRITE);
>  	ssize_t ret;
>  
>  	ret = iomap_dio_complete(dio);
> -	if (is_write && ret > 0)
> -		ret = generic_write_sync(iocb, ret);
>  	iocb->ki_complete(iocb, ret, 0);

Could be simplified to:

{
 	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);

 	iocb->ki_complete(dio->iocb, iomap_dio_complete(dio); 0);
}

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Christoph Hellwig March 28, 2018, 7:44 a.m. UTC | #2

> +#define IOMAP_DIO_WRITE_SYNC	(1 << 29)

Actually based on the next patch can we rename this to something like:
IOMAP_DIO_NEED_SYNC?  That makes the usage a little more clear.

Patch

diff --git a/fs/iomap.c b/fs/iomap.c
index afd163586aa0..f5d4e348bc9b 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -685,6 +685,7 @@  EXPORT_SYMBOL_GPL(iomap_seek_data);
  * Private flags for iomap_dio, must not overlap with the public ones in
  * iomap.h:
  */
+#define IOMAP_DIO_WRITE_SYNC	(1 << 29)
 #define IOMAP_DIO_WRITE		(1 << 30)
 #define IOMAP_DIO_DIRTY		(1 << 31)
 
@@ -759,6 +760,13 @@  static ssize_t iomap_dio_complete(struct iomap_dio *dio)
 			dio_warn_stale_pagecache(iocb->ki_filp);
 	}
 
+	/*
+	 * If this is a DSYNC write, make sure we push it to stable storage now
+	 * that we've written data.
+	 */
+	if (ret > 0 && (dio->flags & IOMAP_DIO_WRITE_SYNC))
+		ret = generic_write_sync(iocb, ret);
+
 	inode_dio_end(file_inode(iocb->ki_filp));
 	kfree(dio);
 
@@ -769,12 +777,9 @@  static void iomap_dio_complete_work(struct work_struct *work)
 {
 	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
 	struct kiocb *iocb = dio->iocb;
-	bool is_write = (dio->flags & IOMAP_DIO_WRITE);
 	ssize_t ret;
 
 	ret = iomap_dio_complete(dio);
-	if (is_write && ret > 0)
-		ret = generic_write_sync(iocb, ret);
 	iocb->ki_complete(iocb, ret, 0);
 }
 
@@ -961,6 +966,10 @@  iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 	return copied;
 }
 
+/*
+ * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
+ * is being issued as AIO or not.
+ */
 ssize_t
 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 		const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
@@ -1006,6 +1015,8 @@  iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 			dio->flags |= IOMAP_DIO_DIRTY;
 	} else {
 		dio->flags |= IOMAP_DIO_WRITE;
+		if (iocb->ki_flags & IOCB_DSYNC)
+			dio->flags |= IOMAP_DIO_WRITE_SYNC;
 		flags |= IOMAP_WRITE;
 	}
 
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 6c30f410ca0c..33b1e8b5dc5c 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -570,11 +570,6 @@  xfs_file_dio_aio_write(
 	 * complete fully or fail.
 	 */
 	ASSERT(ret < 0 || ret == count);
-
-	if (ret > 0) {
-		/* Handle various SYNC-type writes */
-		ret = generic_write_sync(iocb, ret);
-	}
 	return ret;
 }