[PATCH 07/10] fs: simplify the generic_write_sync prototype

[Christoph Hellwig <hch@lst.de>]

The kiocb already has the new position, so use that.  The only interesting
case is AIO, where we currently don't bother updating ki_pos.  We're about
to free the kiocb after we're done, so we might as well update it to make
everyone's life simpler.

While we're at it also return the bytes written argument passed in if
we were successful so that the boilerplate error switch code in the
callers can go away.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/block_dev.c     |  8 ++------
 fs/btrfs/file.c    |  7 ++-----
 fs/cifs/file.c     |  7 ++-----
 fs/direct-io.c     | 17 +++++++++--------
 fs/ext4/file.c     |  9 ++-------
 fs/f2fs/file.c     |  9 ++-------
 fs/nfs/direct.c    |  4 +++-
 fs/ntfs/file.c     |  7 ++-----
 fs/udf/file.c      |  4 +---
 fs/xfs/xfs_file.c  |  6 +-----
 include/linux/fs.h | 24 ++++++++++++++++++------
 mm/filemap.c       |  9 ++-------
 12 files changed, 46 insertions(+), 65 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 12a48db..2d404c9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1660,12 +1660,8 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 	blk_start_plug(&plug);
 	ret = __generic_file_write_iter(iocb, from);
-	if (ret > 0) {
-		ssize_t err;
-		err = generic_write_sync(iocb, iocb->ki_pos - ret, ret);
-		if (err < 0)
-			ret = err;
-	}
+	if (ret > 0)
+		ret = generic_write_sync(iocb, ret);
 	blk_finish_plug(&plug);
 	return ret;
 }
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ca642fc..587e1d0 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1851,11 +1851,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	spin_lock(&BTRFS_I(inode)->lock);
 	BTRFS_I(inode)->last_sub_trans = root->log_transid;
 	spin_unlock(&BTRFS_I(inode)->lock);
-	if (num_written > 0) {
-		err = generic_write_sync(iocb, pos, num_written);
-		if (err < 0)
-			num_written = err;
-	}
+	if (num_written > 0)
+		num_written = generic_write_sync(iocb, num_written);
 
 	if (sync)
 		atomic_dec(&BTRFS_I(inode)->sync_writers);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index b5ce3a5..3b5bb62 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2687,11 +2687,8 @@ cifs_writev(struct kiocb *iocb, struct iov_iter *from)
 out:
 	inode_unlock(inode);
 
-	if (rc > 0) {
-		ssize_t err = generic_write_sync(iocb, iocb->ki_pos - rc, rc);
-		if (err < 0)
-			rc = err;
-	}
+	if (rc > 0)
+		rc = generic_write_sync(iocb, rc);
 	up_read(&cinode->lock_sem);
 	return rc;
 }
diff --git a/fs/direct-io.c b/fs/direct-io.c
index e9369dd..f8ae0a6 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -256,6 +256,7 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
 	if (dio->end_io) {
 		int err;
 
+		// XXX: ki_pos??
 		err = dio->end_io(dio->iocb, offset, ret, dio->private);
 		if (err)
 			ret = err;
@@ -265,15 +266,15 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
 		inode_dio_end(dio->inode);
 
 	if (is_async) {
-		if (dio->rw & WRITE) {
-			int err;
-
-			err = generic_write_sync(dio->iocb, offset,
-						 transferred);
-			if (err < 0 && ret > 0)
-				ret = err;
-		}
+		/*
+		 * generic_write_syncgeneric_write_sync expects ki_pos to
+		 * have been updated already, but the submission path only
+		 * does this for synchronous I/O.
+		 */
+		dio->iocb->ki_pos += transferred;
 
+		if (dio->rw & WRITE)
+			ret = generic_write_sync(dio->iocb,  transferred);
 		dio->iocb->ki_complete(dio->iocb, ret, 0);
 	}
 
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index ad19af7c..56ac32c 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -169,13 +169,8 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ret = __generic_file_write_iter(iocb, from);
 	inode_unlock(inode);
 
-	if (ret > 0) {
-		ssize_t err;
-
-		err = generic_write_sync(iocb, iocb->ki_pos - ret, ret);
-		if (err < 0)
-			ret = err;
-	}
+	if (ret > 0)
+		ret = generic_write_sync(iocb, ret);
 	if (o_direct)
 		blk_finish_plug(&plug);
 
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 407cc57..8f2d65b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1882,13 +1882,8 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	}
 	inode_unlock(inode);
 
-	if (ret > 0) {
-		ssize_t err;
-
-		err = generic_write_sync(iocb, iocb->ki_pos - ret, ret);
-		if (err < 0)
-			ret = err;
-	}
+	if (ret > 0)
+		ret = generic_write_sync(iocb, ret);
 	return ret;
 }
 
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 20f1530..5f18775 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -1054,7 +1054,9 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
 			if (i_size_read(inode) < iocb->ki_pos)
 				i_size_write(inode, iocb->ki_pos);
 			spin_unlock(&inode->i_lock);
-			generic_write_sync(iocb, pos, result);
+
+			/* XXX: should check the generic_write_sync retval */
+			generic_write_sync(iocb, result);
 		}
 	}
 	nfs_direct_req_release(dreq);
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 2655d12..01173d9 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1952,12 +1952,9 @@ static ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		written = ntfs_perform_write(file, from, iocb->ki_pos);
 	current->backing_dev_info = NULL;
 	inode_unlock(vi);
-	if (likely(written > 0)) {
-		err = generic_write_sync(iocb, iocb->ki_pos, written);
-		if (err < 0)
-			written = 0;
-	}
 	iocb->ki_pos += written;
+	if (likely(written > 0))
+		written = generic_write_sync(iocb, written);
 	return written ? written : err;
 }
 
diff --git a/fs/udf/file.c b/fs/udf/file.c
index 28e20c4..54d1d1d 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -152,9 +152,7 @@ out:
 
 	if (retval > 0) {
 		mark_inode_dirty(inode);
-		err = generic_write_sync(iocb, iocb->ki_pos - retval, retval);
-		if (err < 0)
-			retval = err;
+		retval = generic_write_sync(iocb, retval);
 	}
 
 	return retval;
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 31079dc..cfab637 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -903,14 +903,10 @@ xfs_file_write_iter(
 		ret = xfs_file_buffered_aio_write(iocb, from);
 
 	if (ret > 0) {
-		ssize_t err;
-
 		XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);
 
 		/* Handle various SYNC-type writes */
-		err = generic_write_sync(iocb, iocb->ki_pos - ret, ret);
-		if (err < 0)
-			ret = err;
+		ret = generic_write_sync(iocb, ret);
 	}
 	return ret;
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b9b1327..661f56a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2477,13 +2477,25 @@ extern int filemap_fdatawrite_range(struct address_space *mapping,
 extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
 			   int datasync);
 extern int vfs_fsync(struct file *file, int datasync);
-static inline int generic_write_sync(struct kiocb *iocb, loff_t pos, loff_t count)
-{
-	if (!(iocb->ki_flags & IOCB_DSYNC))
-		return 0;
-	return vfs_fsync_range(iocb->ki_filp, pos, pos + count - 1,
-			       (iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
+
+/*
+ * Sync the bytes written if this was a synchronous write.  Expect ki_pos
+ * to already be updated for the write, and will return either the amount
+ * of bytes passed in, or an error if syncing the file failed.
+ */
+static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count)
+{
+	if (iocb->ki_flags & IOCB_DSYNC) {
+		int ret = vfs_fsync_range(iocb->ki_filp,
+				iocb->ki_pos - count, iocb->ki_pos - 1,
+				(iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
+		if (ret)
+			return ret;
+	}
+
+	return count;
 }
+
 extern void emergency_sync(void);
 extern void emergency_remount(void);
 #ifdef CONFIG_BLOCK
diff --git a/mm/filemap.c b/mm/filemap.c
index cc44b1d..e3a6662 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2791,13 +2791,8 @@ ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		ret = __generic_file_write_iter(iocb, from);
 	inode_unlock(inode);
 
-	if (ret > 0) {
-		ssize_t err;
-
-		err = generic_write_sync(iocb, iocb->ki_pos - ret, ret);
-		if (err < 0)
-			ret = err;
-	}
+	if (ret > 0)
+		ret = generic_write_sync(iocb, ret);
 	return ret;
 }
 EXPORT_SYMBOL(generic_file_write_iter);
-- 
2.1.4