[PATCH v2 2/3] virtiofs: Retry hiprio FORGET when virtqueue_add_outbuf() returns -ENOMEM

[Li Wang]

The -ENOMEM from virtqueue_add_outbuf() under GFP_ATOMIC is typically transient.  
Queue the FORGET on queued_reqs and return 1 so the hiprio worker backs off and 
retries instead of dropping the forget.

This matches the existing -ENOSPC handling and avoids silent loss of
nlookup decrements under memory pressure.

Signed-off-by: Li Wang <liwang@xxxxxxxxxx>
---
 fs/fuse/virtio_fs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index bcba1210c797..7e4c3fa6ab57 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -611,8 +611,8 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work)
 }
 
 /*
- * Returns 1 if queue is full and sender should wait a bit before sending
- * next request, 0 otherwise.
+ * Returns 1 if the hiprio queue is full or transient allocation failed and
+ * the caller should wait before submitting the next FORGET, 0 otherwise.
  */
 static int send_forget_request(struct virtio_fs_vq *fsvq,
 			       struct virtio_fs_forget *forget,
@@ -638,13 +638,13 @@ static int send_forget_request(struct virtio_fs_vq *fsvq,
 
 	ret = virtqueue_add_outbuf(vq, &sg, 1, forget, GFP_ATOMIC);
 	if (ret < 0) {
-		if (ret == -ENOSPC) {
+		if (ret == -ENOSPC || ret == -ENOMEM) {
 			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Will try later\n",
 				 ret);
 			list_add_tail(&forget->list, &fsvq->queued_reqs);
 			if (!in_flight)
 				inc_in_flight_req(fsvq);
-			/* Queue is full */
+			/* Queue full or GFP_ATOMIC allocation failure; retry later */
 			ret = 1;
 		} else {
 			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
-- 
2.34.1