xfs: prepare xfs_break_layouts() to be called with XFS_MMAPLOCK_EXCL

In preparation for adding coordination between extent unmap operations
and busy dax-pages, update xfs_break_layouts() to permit it to be called
with the mmap lock held. This lock scheme will be required for
coordinating the break of 'dax layouts' (non-idle dax (ZONE_DEVICE)
pages mapped into the file's address space). Breaking dax layouts will
be added to xfs_break_layouts() in a future patch, for now this preps
the unmap call sites to take and hold XFS_MMAPLOCK_EXCL over the call to
xfs_break_layouts().

Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index a3ed3c811dfa..138fb36ca875 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1031,13 +1031,17 @@ xfs_vn_setattr(
 
         if (iattr->ia_valid & ATTR_SIZE) {
                 struct xfs_inode        *ip = XFS_I(d_inode(dentry));
-                uint                    iolock = XFS_IOLOCK_EXCL;
+                uint                    iolock;
+
+                xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+                iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 
                 error = xfs_break_layouts(d_inode(dentry), &iolock);
-                if (error)
+                if (error) {
+                        xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
                         return error;
+                }
 
-                xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
                 error = xfs_vn_setattr_size(dentry, iattr);
                 xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
         } else {