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, 1 insertions, 4 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 299aee4b7b0b..35309bd046be 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -734,7 +734,7 @@ xfs_file_fallocate(
         struct xfs_inode        *ip = XFS_I(inode);
         long                    error;
         enum xfs_prealloc_flags flags = 0;
-        uint                    iolock = XFS_IOLOCK_EXCL;
+        uint                    iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
         loff_t                  new_size = 0;
         bool                    do_file_insert = false;
 
@@ -748,9 +748,6 @@ xfs_file_fallocate(
         if (error)
                 goto out_unlock;
 
-        xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
-        iolock |= XFS_MMAPLOCK_EXCL;
-
         if (mode & FALLOC_FL_PUNCH_HOLE) {
                 error = xfs_free_file_space(ip, offset, len);
                 if (error)