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-rw-r--r--Documentation/filesystems/fuse.txt48
-rw-r--r--fs/fuse/dev.c162
-rw-r--r--fs/fuse/file.c3
-rw-r--r--fs/fuse/fuse_i.h16
-rw-r--r--fs/fuse/inode.c1
-rw-r--r--include/linux/fuse.h7
6 files changed, 205 insertions, 32 deletions
diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt
index 324df27704cc..a584f05403a4 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 6b5f74cb7b54..1e2006caf158 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 ce759414cff9..36f92f181d2f 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 fd65e75e1622..c862df58da92 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 412892905838..e21ef8a3ad30 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 e7a76ec0f05c..9fc48a674b82 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;
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-07 23:37:23 +0000