Only the owner of the mount may read or write these files.
+Interrupting filesystem operations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If a process issuing a FUSE filesystem request is interrupted, the
+following will happen:
+
+ 1) If the request is not yet sent to userspace AND the signal is
+ fatal (SIGKILL or unhandled fatal signal), then the request is
+ dequeued and returns immediately.
+
+ 2) If the request is not yet sent to userspace AND the signal is not
+ fatal, then an 'interrupted' flag is set for the request. When
+ the request has been successfully transfered to userspace and
+ this flag is set, an INTERRUPT request is queued.
+
+ 3) If the request is already sent to userspace, then an INTERRUPT
+ request is queued.
+
+INTERRUPT requests take precedence over other requests, so the
+userspace filesystem will receive queued INTERRUPTs before any others.
+
+The userspace filesystem may ignore the INTERRUPT requests entirely,
+or may honor them by sending a reply to the _original_ request, with
+the error set to EINTR.
+
+It is also possible that there's a race between processing the
+original request and it's INTERRUPT request. There are two possibilities:
+
+ 1) The INTERRUPT request is processed before the original request is
+ processed
+
+ 2) The INTERRUPT request is processed after the original request has
+ been answered
+
+If the filesystem cannot find the original request, it should wait for
+some timeout and/or a number of new requests to arrive, after which it
+should reply to the INTERRUPT request with an EAGAIN error. In case
+1) the INTERRUPT request will be requeued. In case 2) the INTERRUPT
+reply will be ignored.
+
Aborting a filesystem connection
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Solution is basically the same as above.
-An additional problem is that while the write buffer is being
-copied to the request, the request must not be interrupted. This
-is because the destination address of the copy may not be valid
-after the request is interrupted.
+An additional problem is that while the write buffer is being copied
+to the request, the request must not be interrupted/aborted. This is
+because the destination address of the copy may not be valid after the
+request has returned.
This is solved with doing the copy atomically, and allowing abort
while the page(s) belonging to the write buffer are faulted with
{
memset(req, 0, sizeof(*req));
INIT_LIST_HEAD(&req->list);
+ INIT_LIST_HEAD(&req->intr_entry);
init_waitqueue_head(&req->waitq);
atomic_set(&req->count, 1);
}
void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
req->end = NULL;
list_del(&req->list);
+ list_del(&req->intr_entry);
req->state = FUSE_REQ_FINISHED;
if (req->background) {
if (fc->num_background == FUSE_MAX_BACKGROUND) {
fuse_put_request(fc, req);
}
+static void wait_answer_interruptible(struct fuse_conn *fc,
+ struct fuse_req *req)
+{
+ if (signal_pending(current))
+ return;
+
+ spin_unlock(&fc->lock);
+ wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED);
+ spin_lock(&fc->lock);
+}
+
+static void queue_interrupt(struct fuse_conn *fc, struct fuse_req *req)
+{
+ list_add_tail(&req->intr_entry, &fc->interrupts);
+ wake_up(&fc->waitq);
+ kill_fasync(&fc->fasync, SIGIO, POLL_IN);
+}
+
/* Called with fc->lock held. Releases, and then reacquires it. */
static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
{
- sigset_t oldset;
+ if (!fc->no_interrupt) {
+ /* Any signal may interrupt this */
+ wait_answer_interruptible(fc, req);
- spin_unlock(&fc->lock);
- if (req->force)
+ if (req->aborted)
+ goto aborted;
+ if (req->state == FUSE_REQ_FINISHED)
+ return;
+
+ req->interrupted = 1;
+ if (req->state == FUSE_REQ_SENT)
+ queue_interrupt(fc, req);
+ }
+
+ if (req->force) {
+ spin_unlock(&fc->lock);
wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
- else {
+ spin_lock(&fc->lock);
+ } else {
+ sigset_t oldset;
+
+ /* Only fatal signals may interrupt this */
block_sigs(&oldset);
- wait_event_interruptible(req->waitq,
- req->state == FUSE_REQ_FINISHED);
+ wait_answer_interruptible(fc, req);
restore_sigs(&oldset);
}
- spin_lock(&fc->lock);
- if (req->state == FUSE_REQ_FINISHED && !req->aborted)
- return;
- if (!req->aborted) {
- req->out.h.error = -EINTR;
- req->aborted = 1;
- }
+ if (req->aborted)
+ goto aborted;
+ if (req->state == FUSE_REQ_FINISHED)
+ return;
+
+ req->out.h.error = -EINTR;
+ req->aborted = 1;
+
+ aborted:
if (req->locked) {
/* This is uninterruptible sleep, because data is
being copied to/from the buffers of req. During
return nbytes;
}
+static u64 fuse_get_unique(struct fuse_conn *fc)
+ {
+ fc->reqctr++;
+ /* zero is special */
+ if (fc->reqctr == 0)
+ fc->reqctr = 1;
+
+ return fc->reqctr;
+}
+
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
- fc->reqctr++;
- /* zero is special */
- if (fc->reqctr == 0)
- fc->reqctr = 1;
- req->in.h.unique = fc->reqctr;
+ req->in.h.unique = fuse_get_unique(fc);
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
list_add_tail(&req->list, &fc->pending);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
-/*
- * This can only be interrupted by a SIGKILL
- */
void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
return err;
}
+static int request_pending(struct fuse_conn *fc)
+{
+ return !list_empty(&fc->pending) || !list_empty(&fc->interrupts);
+}
+
/* Wait until a request is available on the pending list */
static void request_wait(struct fuse_conn *fc)
{
DECLARE_WAITQUEUE(wait, current);
add_wait_queue_exclusive(&fc->waitq, &wait);
- while (fc->connected && list_empty(&fc->pending)) {
+ while (fc->connected && !request_pending(fc)) {
set_current_state(TASK_INTERRUPTIBLE);
if (signal_pending(current))
break;
remove_wait_queue(&fc->waitq, &wait);
}
+/*
+ * Transfer an interrupt request to userspace
+ *
+ * Unlike other requests this is assembled on demand, without a need
+ * to allocate a separate fuse_req structure.
+ *
+ * Called with fc->lock held, releases it
+ */
+static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_req *req,
+ const struct iovec *iov, unsigned long nr_segs)
+{
+ struct fuse_copy_state cs;
+ struct fuse_in_header ih;
+ struct fuse_interrupt_in arg;
+ unsigned reqsize = sizeof(ih) + sizeof(arg);
+ int err;
+
+ list_del_init(&req->intr_entry);
+ req->intr_unique = fuse_get_unique(fc);
+ memset(&ih, 0, sizeof(ih));
+ memset(&arg, 0, sizeof(arg));
+ ih.len = reqsize;
+ ih.opcode = FUSE_INTERRUPT;
+ ih.unique = req->intr_unique;
+ arg.unique = req->in.h.unique;
+
+ spin_unlock(&fc->lock);
+ if (iov_length(iov, nr_segs) < reqsize)
+ return -EINVAL;
+
+ fuse_copy_init(&cs, fc, 1, NULL, iov, nr_segs);
+ err = fuse_copy_one(&cs, &ih, sizeof(ih));
+ if (!err)
+ err = fuse_copy_one(&cs, &arg, sizeof(arg));
+ fuse_copy_finish(&cs);
+
+ return err ? err : reqsize;
+}
+
/*
* Read a single request into the userspace filesystem's buffer. This
* function waits until a request is available, then removes it from
spin_lock(&fc->lock);
err = -EAGAIN;
if ((file->f_flags & O_NONBLOCK) && fc->connected &&
- list_empty(&fc->pending))
+ !request_pending(fc))
goto err_unlock;
request_wait(fc);
if (!fc->connected)
goto err_unlock;
err = -ERESTARTSYS;
- if (list_empty(&fc->pending))
+ if (!request_pending(fc))
goto err_unlock;
+ if (!list_empty(&fc->interrupts)) {
+ req = list_entry(fc->interrupts.next, struct fuse_req,
+ intr_entry);
+ return fuse_read_interrupt(fc, req, iov, nr_segs);
+ }
+
req = list_entry(fc->pending.next, struct fuse_req, list);
req->state = FUSE_REQ_READING;
list_move(&req->list, &fc->io);
else {
req->state = FUSE_REQ_SENT;
list_move_tail(&req->list, &fc->processing);
+ if (req->interrupted)
+ queue_interrupt(fc, req);
spin_unlock(&fc->lock);
}
return reqsize;
list_for_each(entry, &fc->processing) {
struct fuse_req *req;
req = list_entry(entry, struct fuse_req, list);
- if (req->in.h.unique == unique)
+ if (req->in.h.unique == unique || req->intr_unique == unique)
return req;
}
return NULL;
goto err_unlock;
req = request_find(fc, oh.unique);
- err = -EINVAL;
if (!req)
goto err_unlock;
request_end(fc, req);
return -ENOENT;
}
+ /* Is it an interrupt reply? */
+ if (req->intr_unique == oh.unique) {
+ err = -EINVAL;
+ if (nbytes != sizeof(struct fuse_out_header))
+ goto err_unlock;
+
+ if (oh.error == -ENOSYS)
+ fc->no_interrupt = 1;
+ else if (oh.error == -EAGAIN)
+ queue_interrupt(fc, req);
+
+ spin_unlock(&fc->lock);
+ fuse_copy_finish(&cs);
+ return nbytes;
+ }
+
+ req->state = FUSE_REQ_WRITING;
list_move(&req->list, &fc->io);
req->out.h = oh;
req->locked = 1;
spin_lock(&fc->lock);
if (!fc->connected)
mask = POLLERR;
- else if (!list_empty(&fc->pending))
+ else if (request_pending(fc))
mask |= POLLIN | POLLRDNORM;
spin_unlock(&fc->lock);
projects / openwrt / staging / blogic.git / commitdiff