xfs: remove xfs_filemap_map_pages() wrapper

Patch series "Prevent ->map_pages from sleeping", v2.

In preparation for a larger patch series which will handle (some, easy)
page faults protected only by RCU, change the two filesystems which have
sleeping locks to not take them and hold the RCU lock around calls to
->map_page to prevent other filesystems from adding sleeping locks.


This patch (of 3):

XFS doesn't actually need to be holding the XFS_MMAPLOCK_SHARED to do
this. filemap_map_pages() cannot bring new folios into the page cache
and the folio lock is taken during filemap_map_pages() which provides
sufficient protection against a truncation or hole punch.

Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: Dave Chinner <[e-mail]>
Cc: Darrick J. Wong <[e-mail]>
Cc: David Howells <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/xfs/xfs_file.c

···
 	return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true);
 }
 
-static vm_fault_t
-xfs_filemap_map_pages(
-	struct vm_fault		*vmf,
-	pgoff_t			start_pgoff,
-	pgoff_t			end_pgoff)
-{
-	struct inode		*inode = file_inode(vmf->vma->vm_file);
-	vm_fault_t ret;
-
-	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = filemap_map_pages(vmf, start_pgoff, end_pgoff);
-	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	return ret;
-}
-
 static const struct vm_operations_struct xfs_file_vm_ops = {
 	.fault		= xfs_filemap_fault,
 	.huge_fault	= xfs_filemap_huge_fault,
-	.map_pages	= xfs_filemap_map_pages,
+	.map_pages	= filemap_map_pages,
 	.page_mkwrite	= xfs_filemap_page_mkwrite,
 	.pfn_mkwrite	= xfs_filemap_pfn_mkwrite,
 };