Patch "mm: never attempt async page lock if we've transferred data already" has been added to the 5.9-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    mm: never attempt async page lock if we've transferred data already

to the 5.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-never-attempt-async-page-lock-if-we-ve-transferred-data-already.patch
and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 0abed7c69b956d135cb6d320c350b2adb213e7d8 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Mon, 16 Nov 2020 13:36:24 -0700
Subject: mm: never attempt async page lock if we've transferred data already

From: Jens Axboe <axboe@xxxxxxxxx>

commit 0abed7c69b956d135cb6d320c350b2adb213e7d8 upstream.

We catch the case where we enter generic_file_buffered_read() with data
already transferred, but we also need to be careful not to allow an async
page lock if we're looping transferring data. If not, we could be
returning -EIOCBQUEUED instead of the transferred amount, and it could
result in double waitqueue additions as well.

Cc: stable@xxxxxxxxxxxxxxx # v5.9
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/filemap.c |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2327,10 +2327,15 @@ 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;
 
@@ -2373,10 +2378,15 @@ 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;


Patches currently in stable-queue which might be from axboe@xxxxxxxxx are

queue-5.9/io_uring-don-t-double-complete-failed-reissue-request.patch
queue-5.9/mm-never-attempt-async-page-lock-if-we-ve-transferred-data-already.patch
queue-5.9/s390-dasd-fix-null-pointer-dereference-for-erp-requests.patch
queue-5.9/usb-dwc2-avoid-leaving-the-error_debugfs-label-unuse.patch
queue-5.9/blk-cgroup-fix-a-hd_struct-leak-in-blkcg_fill_root_iostats.patch