[PATCH v2 09/30] fuse: add fuse_iqueue_ops callbacks

From: Vivek Goyal
Date: Wed May 15 2019 - 15:29:48 EST

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From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>

The /dev/fuse device uses fiq->waitq and fasync to signal that requests
are available. These mechanisms do not apply to virtio-fs. This patch
introduces callbacks so alternative behavior can be used.

Note that queue_interrupt() changes along these lines:

spin_lock(&fiq->waitq.lock);
wake_up_locked(&fiq->waitq);
+ kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
spin_unlock(&fiq->waitq.lock);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);

Since queue_request() and queue_forget() also call kill_fasync() inside
the spinlock this should be safe.

Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/fuse/cuse.c | 2 +-
fs/fuse/dev.c | 50 ++++++++++++++++++++++++++++++++----------------
fs/fuse/fuse_i.h | 48 +++++++++++++++++++++++++++++++++++++++++++++-
fs/fuse/inode.c | 16 ++++++++++++----
4 files changed, 94 insertions(+), 22 deletions(-)

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 55a26f351467..a6ed7a036b50 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -504,7 +504,7 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
* Limit the cuse channel to requests that can
* be represented in file->f_cred->user_ns.
*/
- fuse_conn_init(&cc->fc, file->f_cred->user_ns);
+ fuse_conn_init(&cc->fc, file->f_cred->user_ns, &fuse_dev_fiq_ops, NULL);

fud = fuse_dev_alloc(&cc->fc);
if (!fud) {
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 42fd3b576686..ef489beadf58 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -375,13 +375,33 @@ static unsigned int fuse_req_hash(u64 unique)
return hash_long(unique & ~FUSE_INT_REQ_BIT, FUSE_PQ_HASH_BITS);
}

-static void queue_request(struct fuse_iqueue *fiq, struct fuse_req *req)
+/**
+ * A new request is available, wake fiq->waitq
+ */
+static void fuse_dev_wake_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->waitq.lock)
{
- req->in.h.len = sizeof(struct fuse_in_header) +
- fuse_len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
- list_add_tail(&req->list, &fiq->pending);
wake_up_locked(&fiq->waitq);
kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+ spin_unlock(&fiq->waitq.lock);
+}
+
+const struct fuse_iqueue_ops fuse_dev_fiq_ops = {
+ .wake_forget_and_unlock = fuse_dev_wake_and_unlock,
+ .wake_interrupt_and_unlock = fuse_dev_wake_and_unlock,
+ .wake_pending_and_unlock = fuse_dev_wake_and_unlock,
+};
+EXPORT_SYMBOL_GPL(fuse_dev_fiq_ops);
+
+static void queue_request_and_unlock(struct fuse_iqueue *fiq,
+ struct fuse_req *req)
+__releases(fiq->waitq.lock)
+{
+ req->in.h.len = sizeof(struct fuse_in_header) +
+ fuse_len_args(req->in.numargs,
+ (struct fuse_arg *) req->in.args);
+ list_add_tail(&req->list, &fiq->pending);
+ fiq->ops->wake_pending_and_unlock(fiq);
}

void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
@@ -396,12 +416,11 @@ void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
if (fiq->connected) {
fiq->forget_list_tail->next = forget;
fiq->forget_list_tail = forget;
- wake_up_locked(&fiq->waitq);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+ fiq->ops->wake_forget_and_unlock(fiq);
} else {
kfree(forget);
+ spin_unlock(&fiq->waitq.lock);
}
- spin_unlock(&fiq->waitq.lock);
}

static void flush_bg_queue(struct fuse_conn *fc)
@@ -417,8 +436,7 @@ static void flush_bg_queue(struct fuse_conn *fc)
fc->active_background++;
spin_lock(&fiq->waitq.lock);
req->in.h.unique = fuse_get_unique(fiq);
- queue_request(fiq, req);
- spin_unlock(&fiq->waitq.lock);
+ queue_request_and_unlock(fiq, req);
}
}

@@ -506,10 +524,10 @@ static int queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
spin_unlock(&fiq->waitq.lock);
return 0;
}
- wake_up_locked(&fiq->waitq);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+ fiq->ops->wake_interrupt_and_unlock(fiq);
+ } else {
+ spin_unlock(&fiq->waitq.lock);
}
- spin_unlock(&fiq->waitq.lock);
return 0;
}

@@ -569,11 +587,10 @@ static void __fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
req->out.h.error = -ENOTCONN;
} else {
req->in.h.unique = fuse_get_unique(fiq);
- queue_request(fiq, req);
/* acquire extra reference, since request is still needed
after fuse_request_end() */
__fuse_get_request(req);
- spin_unlock(&fiq->waitq.lock);
+ queue_request_and_unlock(fiq, req);

request_wait_answer(fc, req);
/* Pairs with smp_wmb() in fuse_request_end() */
@@ -706,10 +723,11 @@ static int fuse_request_send_notify_reply(struct fuse_conn *fc,
req->in.h.unique = unique;
spin_lock(&fiq->waitq.lock);
if (fiq->connected) {
- queue_request(fiq, req);
+ queue_request_and_unlock(fiq, req);
err = 0;
+ } else {
+ spin_unlock(&fiq->waitq.lock);
}
- spin_unlock(&fiq->waitq.lock);

return err;
}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 84f094e4ac36..0b578e07156d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -71,6 +71,12 @@ struct fuse_mount_data {
unsigned max_read;
unsigned blksize;

+ /* fuse input queue operations */
+ const struct fuse_iqueue_ops *fiq_ops;
+
+ /* device-specific state for fuse_iqueue */
+ void *fiq_priv;
+
/* fuse_dev pointer to fill in, should contain NULL on entry */
void **fudptr;
};
@@ -461,6 +467,39 @@ struct fuse_req {
struct file *stolen_file;
};

+struct fuse_iqueue;
+
+/**
+ * Input queue callbacks
+ *
+ * Input queue signalling is device-specific. For example, the /dev/fuse file
+ * uses fiq->waitq and fasync to wake processes that are waiting on queue
+ * readiness. These callbacks allow other device types to respond to input
+ * queue activity.
+ */
+struct fuse_iqueue_ops {
+ /**
+ * Signal that a forget has been queued
+ */
+ void (*wake_forget_and_unlock)(struct fuse_iqueue *fiq)
+ __releases(fiq->waitq.lock);
+
+ /**
+ * Signal that an INTERRUPT request has been queued
+ */
+ void (*wake_interrupt_and_unlock)(struct fuse_iqueue *fiq)
+ __releases(fiq->waitq.lock);
+
+ /**
+ * Signal that a request has been queued
+ */
+ void (*wake_pending_and_unlock)(struct fuse_iqueue *fiq)
+ __releases(fiq->waitq.lock);
+};
+
+/** /dev/fuse input queue operations */
+extern const struct fuse_iqueue_ops fuse_dev_fiq_ops;
+
struct fuse_iqueue {
/** Connection established */
unsigned connected;
@@ -486,6 +525,12 @@ struct fuse_iqueue {

/** O_ASYNC requests */
struct fasync_struct *fasync;
+
+ /** Device-specific callbacks */
+ const struct fuse_iqueue_ops *ops;
+
+ /** Device-specific state */
+ void *priv;
};

#define FUSE_PQ_HASH_BITS 8
@@ -997,7 +1042,8 @@ struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
/**
* Initialize fuse_conn
*/
-void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns);
+void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
+ const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv);

/**
* Release reference to fuse_conn
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index baf2966a753a..126e77854dac 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -570,7 +570,9 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
return 0;
}

-static void fuse_iqueue_init(struct fuse_iqueue *fiq)
+static void fuse_iqueue_init(struct fuse_iqueue *fiq,
+ const struct fuse_iqueue_ops *ops,
+ void *priv)
{
memset(fiq, 0, sizeof(struct fuse_iqueue));
init_waitqueue_head(&fiq->waitq);
@@ -578,6 +580,8 @@ static void fuse_iqueue_init(struct fuse_iqueue *fiq)
INIT_LIST_HEAD(&fiq->interrupts);
fiq->forget_list_tail = &fiq->forget_list_head;
fiq->connected = 1;
+ fiq->ops = ops;
+ fiq->priv = priv;
}

static void fuse_pqueue_init(struct fuse_pqueue *fpq)
@@ -591,7 +595,8 @@ static void fuse_pqueue_init(struct fuse_pqueue *fpq)
fpq->connected = 1;
}

-void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
+void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
+ const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)
{
memset(fc, 0, sizeof(*fc));
spin_lock_init(&fc->lock);
@@ -601,7 +606,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
atomic_set(&fc->dev_count, 1);
init_waitqueue_head(&fc->blocked_waitq);
init_waitqueue_head(&fc->reserved_req_waitq);
- fuse_iqueue_init(&fc->iq);
+ fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);
INIT_LIST_HEAD(&fc->bg_queue);
INIT_LIST_HEAD(&fc->entry);
INIT_LIST_HEAD(&fc->devices);
@@ -1113,7 +1118,8 @@ int fuse_fill_super_common(struct super_block *sb,
if (!fc)
goto err;

- fuse_conn_init(fc, sb->s_user_ns);
+ fuse_conn_init(fc, sb->s_user_ns, mount_data->fiq_ops,
+ mount_data->fiq_priv);
fc->release = fuse_free_conn;

fud = fuse_dev_alloc(fc);
@@ -1215,6 +1221,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
goto err_fput;
__set_bit(FR_BACKGROUND, &init_req->flags);

+ d.fiq_ops = &fuse_dev_fiq_ops;
+ d.fiq_priv = NULL;
d.fudptr = &file->private_data;
err = fuse_fill_super_common(sb, &d);
if (err < 0)
--
2.20.1

Next message: Vivek Goyal: "[PATCH v2 08/30] fuse: extract fuse_fill_super_common()"
Previous message: Vivek Goyal: "[PATCH v2 00/30] [RFC] virtio-fs: shared file system for virtual machines"
In reply to: Vivek Goyal: "[PATCH v2 06/30] fuse: Export fuse_send_init_request()"
Next in thread: Vivek Goyal: "[PATCH v2 08/30] fuse: extract fuse_fill_super_common()"
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