xfs: reflink should break pnfs leases before sharing blocks

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.  The
structure of this function sets us up for the lock contention reduction
in the next patch.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index bcc2ad4f0899714621f6de37cb55c4a84ea885e5..bac464f0bc59fe7c0d31a8231c13eb61120c9bda 100644 (file)
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1244,6 +1244,50 @@ err:
        return error;
 }
 
+/*
+ * 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)
+{
+       int                     error;
+
+retry:
+       if (src < dest) {
+               inode_lock(src);
+               inode_lock_nested(dest, I_MUTEX_NONDIR2);
+       } else {
+               /* src >= dest */
+               inode_lock(dest);
+       }
+
+       error = break_layout(dest, false);
+       if (error == -EWOULDBLOCK) {
+               inode_unlock(dest);
+               if (src < dest)
+                       inode_unlock(src);
+               error = break_layout(dest, true);
+               if (error)
+                       return error;
+               goto retry;
+       }
+       if (error) {
+               inode_unlock(dest);
+               if (src < dest)
+                       inode_unlock(src);
+               return error;
+       }
+       if (src > dest)
+               inode_lock_nested(src, I_MUTEX_NONDIR2);
+       return 0;
+}
+
 /*
  * Link a range of blocks from one file to another.
  */
@@ -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