mm: drop per-VMA lock when returning VM_FAULT_RETRY or VM_FAULT_COMPLETED

handle_mm_fault returning VM_FAULT_RETRY or VM_FAULT_COMPLETED means
mmap_lock has been released.  However with per-VMA locks behavior is
different and the caller should still release it.  To make the rules
consistent for the caller, drop the per-VMA lock when returning
VM_FAULT_RETRY or VM_FAULT_COMPLETED.  Currently the only path returning
VM_FAULT_RETRY under per-VMA locks is do_swap_page and no path returns
VM_FAULT_COMPLETED for now.

[[email protected]: fix riscv]
  Link: https://lkml.kernel.org/r/CAJuCfpE6GWEx1rPBmNpUfoD5o-gNFz9-UFywzCE2PbEGBiVz7g@mail.gmail.com
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Acked-by: Peter Xu <[email protected]>
Tested-by: Conor Dooley <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Howells <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Punit Agrawal <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 12 insertions, 0 deletions

diff --git a/mm/memory.c b/mm/memory.c
index f9c3ad489823..b9c3780fd426 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3747,6 +3747,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 
 	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
 		ret = VM_FAULT_RETRY;
+		vma_end_read(vma);
 		goto out;
 	}
 
@@ -5248,6 +5249,17 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma,
 				 !is_cow_mapping(vma->vm_flags)))
 			return VM_FAULT_SIGSEGV;
 	}
+#ifdef CONFIG_PER_VMA_LOCK
+	/*
+	 * Per-VMA locks can't be used with FAULT_FLAG_RETRY_NOWAIT because of
+	 * the assumption that lock is dropped on VM_FAULT_RETRY.
+	 */
+	if (WARN_ON_ONCE((*flags &
+			(FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)) ==
+			(FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)))
+		return VM_FAULT_SIGSEGV;
+#endif
+
 	return 0;
 }