Merge tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-hirsute-kernel.git] / mm / filemap.c

diff --git a/mm/filemap.c b/mm/filemap.c
index d5e7c2029d16b4d8d8801d1058221b645904d5d7..0b2067b3c32831aa1617123b3dc964d479cbd9d1 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1484,11 +1484,19 @@ void end_page_writeback(struct page *page)
                rotate_reclaimable_page(page);
        }
 
+       /*
+        * Writeback does not hold a page reference of its own, relying
+        * on truncation to wait for the clearing of PG_writeback.
+        * But here we must make sure that the page is not freed and
+        * reused before the wake_up_page().
+        */
+       get_page(page);
        if (!test_clear_page_writeback(page))
                BUG();
 
        smp_mb__after_atomic();
        wake_up_page(page, PG_writeback);
+       put_page(page);
 }
 EXPORT_SYMBOL(end_page_writeback);
 
@@ -2347,10 +2355,15 @@ page_ok:
 
 page_not_up_to_date:
                /* Get exclusive access to the page ... */
-               if (iocb->ki_flags & IOCB_WAITQ)
+               if (iocb->ki_flags & IOCB_WAITQ) {
+                       if (written) {
+                               put_page(page);
+                               goto out;
+                       }
                        error = lock_page_async(page, iocb->ki_waitq);
-               else
+               } else {
                        error = lock_page_killable(page);
+               }
                if (unlikely(error))
                        goto readpage_error;
 
@@ -2393,10 +2406,15 @@ readpage:
                }
 
                if (!PageUptodate(page)) {
-                       if (iocb->ki_flags & IOCB_WAITQ)
+                       if (iocb->ki_flags & IOCB_WAITQ) {
+                               if (written) {
+                                       put_page(page);
+                                       goto out;
+                               }
                                error = lock_page_async(page, iocb->ki_waitq);
-                       else
+                       } else {
                                error = lock_page_killable(page);
+                       }
 
                        if (unlikely(error))
                                goto readpage_error;