[PATCH v3 5/7] btrfs: lock the inode first before flushing range when punching hole

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

When doing hole punching we are flushing delalloc and waiting for ordered
extents to complete before locking the inode (VFS lock and the btrfs
specific i_mmap_lock). This is fine because even if a write happens after
we call btrfs_wait_ordered_range() and before we lock the inode (call
btrfs_inode_lock()), we will notice the write at
btrfs_punch_hole_lock_range() and flush delalloc and wait for its ordered
extent.

We can however make this simpler by locking first the inode an then call
btrfs_wait_ordered_range(), which will allow us to remove the ordered
extent lookup logic from btrfs_punch_hole_lock_range() in the next patch.
It also makes the behaviour the same as plain fallocate, hole punching
and reflinks.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index a7fd05c1d52f..56c7961d165b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2976,11 +2976,12 @@ static int btrfs_punch_hole(struct file *file, loff_t offset, loff_t len)
 	bool truncated_block = false;
 	bool updated_inode = false;
 
+	btrfs_inode_lock(inode, BTRFS_ILOCK_MMAP);
+
 	ret = btrfs_wait_ordered_range(inode, offset, len);
 	if (ret)
-		return ret;
+		goto out_only_mutex;
 
-	btrfs_inode_lock(inode, BTRFS_ILOCK_MMAP);
 	ino_size = round_up(inode->i_size, fs_info->sectorsize);
 	ret = find_first_non_hole(BTRFS_I(inode), &offset, &len);
 	if (ret < 0)
-- 
2.33.0