On Mon, 6 Sept 2021 at 14:36, Hao Peng <flyingpenghao@xxxxxxxxx> wrote:
>
> 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 can be realized by putting the request of the processing
> list back into the pending list.
Thanks for the patch.
Do you have example userspace code for this?
>
> Signed-off-by: Peng Hao <flyingpeng@xxxxxxxxxxx>
> ---
> fs/fuse/dev.c | 38 +++++++++++++++++++++++++++++++++++++-
> include/uapi/linux/fuse.h | 1 +
> 2 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 491c092d427b..8e1b69a5b503 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 +2268,42 @@ 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);
> + list_for_each_entry_safe(req, next, &fpq->io, list) {
> + spin_lock(&req->waitq.lock);
> + clear_bit(FR_LOCKED, &req->flags);
> + list_move(&req->list, &recovery);
> + spin_unlock(&req->waitq.lock);
> + }
I don't get it. Recovery means the previous server process is dead.
If there are requests on the fpq->io queue, than that's obviously not
true and having two processes messing with the same requests isn't
going to do any good.
So I suggest just erroring out if fpq->io is not empty.
> + for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
> + list_splice_tail_init(&fpq->processing[i],
> + &recovery);
> + list_for_each_entry_safe(req, next, &recovery, list) {
> + clear_bit(FR_SENT, &req->flags);
> + }
> + spin_unlock(&fpq->lock);
> +
> + spin_lock(&fiq->lock);
> + list_for_each_entry_safe(req, next, &recovery, list) {
> + set_bit(FR_PENDING, &req->flags);
> + }
> + 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
