xfs: use i_mmaplock on write faults

Take the i_mmaplock over write page faults. These come through the
->page_mkwrite callout, so we need to wrap that calls with the
i_mmaplock.

This gives us a lock order of mmap_sem -> i_mmaplock -> page_lock
-> i_lock.

Also, move the page_mkwrite wrapper to the same region of xfs_file.c
as the read fault wrappers and add a tracepoint.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 24 insertions, 15 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index ac174226244a..d55f011401bf 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -991,20 +991,6 @@ xfs_file_mmap(
 }
 
 /*
- * mmap()d file has taken write protection fault and is being made
- * writable. We can set the page state up correctly for a writable
- * page, which means we can do correct delalloc accounting (ENOSPC
- * checking!) and unwritten extent mapping.
- */
-STATIC int
-xfs_vm_page_mkwrite(
-        struct vm_area_struct   *vma,
-        struct vm_fault         *vmf)
-{
-        return block_page_mkwrite(vma, vmf, xfs_get_blocks);
-}
-
-/*
  * This type is designed to indicate the type of offset we would like
  * to search from page cache for xfs_seek_hole_data().
  */
@@ -1405,6 +1391,29 @@ xfs_filemap_fault(
         return error;
 }
 
+/*
+ * mmap()d file has taken write protection fault and is being made writable. We
+ * can set the page state up correctly for a writable page, which means we can
+ * do correct delalloc accounting (ENOSPC checking!) and unwritten extent
+ * mapping.
+ */
+STATIC int
+xfs_filemap_page_mkwrite(
+        struct vm_area_struct   *vma,
+        struct vm_fault         *vmf)
+{
+        struct xfs_inode        *ip = XFS_I(vma->vm_file->f_mapping->host);
+        int                     error;
+
+        trace_xfs_filemap_page_mkwrite(ip);
+
+        xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
+        error = block_page_mkwrite(vma, vmf, xfs_get_blocks);
+        xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+
+        return error;
+}
+
 const struct file_operations xfs_file_operations = {
         .llseek         = xfs_file_llseek,
         .read           = new_sync_read,
@@ -1439,5 +1448,5 @@ const struct file_operations xfs_dir_file_operations = {
 static const struct vm_operations_struct xfs_file_vm_ops = {
         .fault          = xfs_filemap_fault,
         .map_pages      = filemap_map_pages,
-        .page_mkwrite   = xfs_vm_page_mkwrite,
+        .page_mkwrite   = xfs_filemap_page_mkwrite,
 };