[PATCH 01/11] xfs: reflink should break pnfs leases before sharing blocks

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Before we share blocks between files, we need to break the pnfs leases
on the layout before we start slicing and dicing the block map.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_reflink.c |   48 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)


diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 47aea2e..f89a725 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1245,6 +1245,50 @@ xfs_reflink_remap_blocks(
 }
 
 /*
+ * Grab the exclusive iolock for a data copy from src to dest, making
+ * sure to abide vfs locking order (lowest pointer value goes first) and
+ * breaking the pnfs layout leases on dest before proceeding.  The loop
+ * is needed because we cannot call the blocking break_layout() with the
+ * src iolock held, and therefore have to back out both locks.
+ */
+static int
+xfs_iolock_two_inodes_and_break_layout(
+	struct inode		*src,
+	struct inode		*dest)
+{
+	bool			src_first = src < dest;
+	bool			src_last = src > dest;
+	int			error;
+
+retry:
+	if (src_first) {
+		inode_lock(src);
+		inode_lock_nested(dest, I_MUTEX_NONDIR2);
+	} else {
+		inode_lock(dest);
+	}
+
+	error = break_layout(dest, false);
+	if (error == -EWOULDBLOCK) {
+		inode_unlock(dest);
+		if (src_first)
+			inode_unlock(src);
+		error = break_layout(dest, true);
+		if (error)
+			return error;
+		goto retry;
+	} else if (error) {
+		inode_unlock(dest);
+		if (src_first)
+			inode_unlock(src);
+		return error;
+	}
+	if (src_last)
+		inode_lock_nested(src, I_MUTEX_NONDIR2);
+	return 0;
+}
+
+/*
  * Link a range of blocks from one file to another.
  */
 int
@@ -1274,7 +1318,9 @@ xfs_reflink_remap_range(
 		return -EIO;
 
 	/* Lock both files against IO */
-	lock_two_nondirectories(inode_in, inode_out);
+	ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
+	if (ret)
+		return ret;
 	if (same_inode)
 		xfs_ilock(src, XFS_MMAPLOCK_EXCL);
 	else