6 files changed, 205 insertions, 32 deletions

diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt
index 324df27..a584f05 100644
--- a/Documentation/filesystems/fuse.txt
+++ b/Documentation/filesystems/fuse.txt
@@ -124,6 +124,46 @@ For each connection the following files exist within this directory:
 
 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
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -351,10 +391,10 @@ but is caused by a pagefault.
 
 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
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6b5f74c..1e2006c 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -34,6 +34,7 @@ static void fuse_request_init(struct fuse_req *req)
 {
 	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);
 }
@@ -215,6 +216,7 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
 	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) {
@@ -235,28 +237,63 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
 		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
@@ -288,13 +325,19 @@ static unsigned len_args(unsigned numargs, struct fuse_arg *args)
 	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);
@@ -307,9 +350,6 @@ static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
 	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;
@@ -566,13 +606,18 @@ static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
 	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;
@@ -586,6 +631,45 @@ static void request_wait(struct fuse_conn *fc)
 }
 
 /*
+ * 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
  * the pending list and copies request data to userspace buffer.  If
@@ -610,7 +694,7 @@ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
 	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);
@@ -618,9 +702,15 @@ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
 	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);
@@ -658,6 +748,8 @@ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
 	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;
@@ -684,7 +776,7 @@ static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique)
 	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;
@@ -750,7 +842,6 @@ static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov,
 		goto err_unlock;
 
 	req = request_find(fc, oh.unique);
-	err = -EINVAL;
 	if (!req)
 		goto err_unlock;
 
@@ -761,6 +852,23 @@ static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov,
 		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;
@@ -809,7 +917,7 @@ static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
 	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);
 
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ce75941..36f92f1 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -705,6 +705,9 @@ static int fuse_setlk(struct file *file, struct file_lock *fl)
 	fuse_lk_fill(req, file, fl, opcode, pid);
 	request_send(fc, req);
 	err = req->out.h.error;
+	/* locking is restartable */
+	if (err == -EINTR)
+		err = -ERESTARTSYS;
 	fuse_put_request(fc, req);
 	return err;
 }
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index fd65e75..c862df5 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -131,6 +131,7 @@ enum fuse_req_state {
 	FUSE_REQ_PENDING,
 	FUSE_REQ_READING,
 	FUSE_REQ_SENT,
+	FUSE_REQ_WRITING,
 	FUSE_REQ_FINISHED
 };
 
@@ -144,9 +145,15 @@ struct fuse_req {
 	    fuse_conn */
 	struct list_head list;
 
+	/** Entry on the interrupts list  */
+	struct list_head intr_entry;
+
 	/** refcount */
 	atomic_t count;
 
+	/** Unique ID for the interrupt request */
+	u64 intr_unique;
+
 	/*
 	 * The following bitfields are either set once before the
 	 * request is queued or setting/clearing them is protected by
@@ -165,6 +172,9 @@ struct fuse_req {
 	/** Request is sent in the background */
 	unsigned background:1;
 
+	/** The request has been interrupted */
+	unsigned interrupted:1;
+
 	/** Data is being copied to/from the request */
 	unsigned locked:1;
 
@@ -262,6 +272,9 @@ struct fuse_conn {
 	/** Number of requests currently in the background */
 	unsigned num_background;
 
+	/** Pending interrupts */
+	struct list_head interrupts;
+
 	/** Flag indicating if connection is blocked.  This will be
 	    the case before the INIT reply is received, and if there
 	    are too many outstading backgrounds requests */
@@ -320,6 +333,9 @@ struct fuse_conn {
 	/** Is create not implemented by fs? */
 	unsigned no_create : 1;
 
+	/** Is interrupt not implemented by fs? */
+	unsigned no_interrupt : 1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4128929..e21ef8a 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -381,6 +381,7 @@ static struct fuse_conn *new_conn(void)
 		INIT_LIST_HEAD(&fc->pending);
 		INIT_LIST_HEAD(&fc->processing);
 		INIT_LIST_HEAD(&fc->io);
+		INIT_LIST_HEAD(&fc->interrupts);
 		atomic_set(&fc->num_waiting, 0);
 		fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 		fc->bdi.unplug_io_fn = default_unplug_io_fn;
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index e7a76ec..9fc48a6 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -125,7 +125,8 @@ enum fuse_opcode {
 	FUSE_SETLK         = 32,
 	FUSE_SETLKW        = 33,
 	FUSE_ACCESS        = 34,
-	FUSE_CREATE        = 35
+	FUSE_CREATE        = 35,
+	FUSE_INTERRUPT     = 36,
 };
 
 /* The read buffer is required to be at least 8k, but may be much larger */
@@ -291,6 +292,10 @@ struct fuse_init_out {
 	__u32	max_write;
 };
 
+struct fuse_interrupt_in {
+	__u64	unique;
+};
+
 struct fuse_in_header {
 	__u32	len;
 	__u32	opcode;