[PATCH v2 1/6] mm: Make lock_folio_maybe_drop_mmap() VMA lock aware

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Drop the VMA lock instead of the mmap_lock if that's the one which
is held.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/filemap.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 9481ffaf24e6..a598872d62cc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3104,7 +3104,7 @@ static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
 
 	/*
 	 * NOTE! This will make us return with VM_FAULT_RETRY, but with
-	 * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
+	 * the fault lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
 	 * is supposed to work. We have way too many special cases..
 	 */
 	if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
@@ -3114,13 +3114,14 @@ static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
 	if (vmf->flags & FAULT_FLAG_KILLABLE) {
 		if (__folio_lock_killable(folio)) {
 			/*
-			 * We didn't have the right flags to drop the mmap_lock,
-			 * but all fault_handlers only check for fatal signals
-			 * if we return VM_FAULT_RETRY, so we need to drop the
-			 * mmap_lock here and return 0 if we don't have a fpin.
+			 * We didn't have the right flags to drop the
+			 * fault lock, but all fault_handlers only check
+			 * for fatal signals if we return VM_FAULT_RETRY,
+			 * so we need to drop the fault lock here and
+			 * return 0 if we don't have a fpin.
 			 */
 			if (*fpin == NULL)
-				mmap_read_unlock(vmf->vma->vm_mm);
+				release_fault_lock(vmf);
 			return 0;
 		}
 	} else
-- 
2.40.1