On Tue, Sep 7, 2021 at 5:34 PM Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> 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?
>
Under development. When the fuse user-mode file system process is abnormal,
the process does not terminate (/dev/fuse will not be closed), enter
the reset procedure,
and will not open /dev/fuse again during the reinitialization.
Of course, this can only solve part of the abnormal problem.
> > 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.
I will modify it in the next version.
>
>
> > + 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
