[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 d8dc351..a063d4d 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 9d8e22c..a927c12 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 b22b68c..9b51d49 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 f7bcc01..3bf3f20 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_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 5915928..59f3ccc 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 51ed838..28f75a1 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 be86de9..0b9fca0 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 10dc38c..5622ed5 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 8e3d1ae..6325706 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 b5d70e7..cd35409 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 1e61161..250e426 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 8345d6d..182b218 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