Btrfs: add helper btrfs_fdatawrite_range

To avoid duplicating this double filemap_fdatawrite_range() call for
inodes with async extents (compressed writes) so often.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 30 insertions, 9 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index f5a868a..0fbf0e7 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1676,6 +1676,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,
 				    loff_t pos)
 {
 	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
 	ssize_t written;
 	ssize_t written_buffered;
 	loff_t endbyte;
@@ -1697,13 +1698,10 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,
 	 * able to read what was just written.
 	 */
 	endbyte = pos + written_buffered - 1;
-	err = filemap_fdatawrite_range(file->f_mapping, pos, endbyte);
-	if (!err && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
-			     &BTRFS_I(file_inode(file))->runtime_flags))
-		err = filemap_fdatawrite_range(file->f_mapping, pos, endbyte);
+	err = btrfs_fdatawrite_range(inode, pos, endbyte);
 	if (err)
 		goto out;
-	err = filemap_fdatawait_range(file->f_mapping, pos, endbyte);
+	err = filemap_fdatawait_range(inode->i_mapping, pos, endbyte);
 	if (err)
 		goto out;
 	written += written_buffered;
@@ -1864,10 +1862,7 @@ static int start_ordered_ops(struct inode *inode, loff_t start, loff_t end)
 	int ret;
 
 	atomic_inc(&BTRFS_I(inode)->sync_writers);
-	ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
-	if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
-			     &BTRFS_I(inode)->runtime_flags))
-		ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
+	ret = btrfs_fdatawrite_range(inode, start, end);
 	atomic_dec(&BTRFS_I(inode)->sync_writers);
 
 	return ret;
@@ -2820,3 +2815,29 @@ int btrfs_auto_defrag_init(void)
 
 	return 0;
 }
+
+int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end)
+{
+	int ret;
+
+	/*
+	 * So with compression we will find and lock a dirty page and clear the
+	 * first one as dirty, setup an async extent, and immediately return
+	 * with the entire range locked but with nobody actually marked with
+	 * writeback.  So we can't just filemap_write_and_wait_range() and
+	 * expect it to work since it will just kick off a thread to do the
+	 * actual work.  So we need to call filemap_fdatawrite_range _again_
+	 * since it will wait on the page lock, which won't be unlocked until
+	 * after the pages have been marked as writeback and so we're good to go
+	 * from there.  We have to do this otherwise we'll miss the ordered
+	 * extents and that results in badness.  Please Josef, do not think you
+	 * know better and pull this out at some point in the future, it is
+	 * right and you are wrong.
+	 */
+	ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
+	if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
+			     &BTRFS_I(inode)->runtime_flags))
+		ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
+
+	return ret;
+}