[PATCH v2] fuse: add a dev ioctl for recovery

[Peng Hao <flyingpenghao@gmail.com>]

For a simple read-only file system, as long as the connection
is not broken, the recovery of the user-mode read-only file
system process can be realized by putting the request of the
processing list back into the pending list.

Signed-off-by: Peng Hao <flyingpeng@tencent.com>
---
 fs/fuse/dev.c             | 31 ++++++++++++++++++++++++++++++-
 include/uapi/linux/fuse.h |  1 +
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 491c092d427b..9b0f34468494 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2239,7 +2239,7 @@ static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
 static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 			   unsigned long arg)
 {
-	int res;
+	int res = 0;
 	int oldfd;
 	struct fuse_dev *fud = NULL;
 
@@ -2268,6 +2268,35 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 			}
 		}
 		break;
+
+	case FUSE_DEV_IOC_RECOVERY:
+	{
+		struct fuse_iqueue *fiq;
+		struct fuse_pqueue *fpq;
+		struct fuse_req *req, *next;
+		LIST_HEAD(recovery);
+		unsigned int i;
+
+		fud = fuse_get_dev(file);
+		fiq = &fud->fc->iq;
+		fpq = &fud->pq;
+
+		spin_lock(&fpq->lock);
+		for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
+			list_splice_tail_init(&fpq->processing[i],
+					      &recovery);
+		spin_unlock(&fpq->lock);
+
+		list_for_each_entry_safe(req, next, &recovery, list) {
+			clear_bit(FR_SENT, &req->flags);
+			set_bit(FR_PENDING, &req->flags);
+		}
+
+		spin_lock(&fiq->lock);
+		list_splice(&recovery, &fiq->pending);
+		spin_unlock(&fiq->lock);
+		break;
+	}
 	default:
 		res = -ENOTTY;
 		break;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 36ed092227fa..fc07324efa9d 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -923,6 +923,7 @@ struct fuse_notify_retrieve_in {
 /* Device ioctls: */
 #define FUSE_DEV_IOC_MAGIC		229
 #define FUSE_DEV_IOC_CLONE		_IOR(FUSE_DEV_IOC_MAGIC, 0, uint32_t)
+#define FUSE_DEV_IOC_RECOVERY		_IOR(FUSE_DEV_IOC_MAGIC+1, 0, uint32_t)
 
 struct fuse_lseek_in {
 	uint64_t	fh;
-- 
2.27.0