From: "Kirill A. Shutemov" <redacted>

alloc_set_pte() has two users with different requirements: in the
faultaround code, it called from an atomic context and PTE page table
has to be preallocated. finish_fault() can sleep and allocate page table
as needed.

PTL locking rules are also strange, hard to follow and overkill for
finish_fault().

Let's untangle the mess. alloc_set_pte() has gone now. All locking is
explicit.

The price is some code duplication to handle huge pages in faultaround
path, but it should be fine, having overall improvement in readability.

Signed-off-by: Kirill A. Shutemov <redacted>
Signed-off-by: Will Deacon <will@kernel.org>
---
 fs/xfs/xfs_file.c       |   6 +-
 include/linux/mm.h      |  12 ++-
 include/linux/pgtable.h |  11 +++
 mm/filemap.c            | 177 ++++++++++++++++++++++++++---------
 mm/memory.c             | 199 ++++++++++++----------------------------
 5 files changed, 213 insertions(+), 192 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5b0f93f73837..111fe73bb8a7 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c

@@ -1319,17 +1319,19 @@ xfs_filemap_pfn_mkwrite(
 	return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true);
 }
 
-static void
+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);
-	filemap_map_pages(vmf, start_pgoff, end_pgoff);
+	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 = {

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ecdf8a8cd6ae..801dd99f733c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -542,8 +542,8 @@ struct vm_fault {
 					 * is not NULL, otherwise pmd.
 					 */
 	pgtable_t prealloc_pte;		/* Pre-allocated pte page table.
-					 * vm_ops->map_pages() calls
-					 * alloc_set_pte() from atomic context.
+					 * vm_ops->map_pages() sets up a page
+					 * table from from atomic context.
 					 * do_fault_around() pre-allocates
 					 * page table to avoid allocation from
 					 * atomic context.