[PATCH] fuse: add O_ASYNC support to FUSE device

This adds asynchronous notification to FUSE - a FUSE server can request
O_ASYNC on a /dev/fuse file descriptor and receive SIGIO when there is input
available.

One subtlety - fuse_dev_fasync, which is called when O_ASYNC is requested,
does no locking, unlink the other methods.  I think it's unnecessary, as the
fuse_conn.fasync list is manipulated only by fasync_helper and kill_fasync,
which provide their own locking.  It would also be wrong to use the fuse_lock,
as it's a spin lock and fasync_helper can sleep.  My one concern with this is
the fuse_conn going away underneath fuse_dev_fasync - sys_fcntl takes a
reference on the file struct, so this seems not to be a problem.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index b2e8613..438770f 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -317,6 +317,7 @@ static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
        list_add_tail(&req->list, &fc->pending);
        req->state = FUSE_REQ_PENDING;
        wake_up(&fc->waitq);
+       kill_fasync(&fc->fasync, SIGIO, POLL_IN);
 }
 
 /*
@@ -901,6 +902,7 @@ void fuse_abort_conn(struct fuse_conn *fc)
                end_requests(fc, &fc->pending);
                end_requests(fc, &fc->processing);
                wake_up_all(&fc->waitq);
+               kill_fasync(&fc->fasync, SIGIO, POLL_IN);
        }
        spin_unlock(&fuse_lock);
 }
@@ -917,12 +919,24 @@ static int fuse_dev_release(struct inode *inode, struct file *file)
                end_requests(fc, &fc->processing);
        }
        spin_unlock(&fuse_lock);
-       if (fc)
+       if (fc) {
+               fasync_helper(-1, file, 0, &fc->fasync);
                kobject_put(&fc->kobj);
+       }
 
        return 0;
 }
 
+static int fuse_dev_fasync(int fd, struct file *file, int on)
+{
+       struct fuse_conn *fc = fuse_get_conn(file);
+       if (!fc)
+               return -ENODEV;
+
+       /* No locking - fasync_helper does its own locking */
+       return fasync_helper(fd, file, on, &fc->fasync);
+}
+
 const struct file_operations fuse_dev_operations = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
@@ -932,6 +946,7 @@ const struct file_operations fuse_dev_operations = {
        .writev         = fuse_dev_writev,
        .poll           = fuse_dev_poll,
        .release        = fuse_dev_release,
+       .fasync         = fuse_dev_fasync,
 };
 
 static struct miscdevice fuse_miscdevice = {

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index a16a04f..e5cb46b 100644 (file)
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -318,6 +318,9 @@ struct fuse_conn {
 
        /** kobject */
        struct kobject kobj;
+
+       /** O_ASYNC requests */
+       struct fasync_struct *fasync;
 };
 
 static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 879e6fb..78700cb 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -216,6 +216,7 @@ static void fuse_put_super(struct super_block *sb)
        spin_unlock(&fuse_lock);
        up_write(&fc->sbput_sem);
        /* Flush all readers on this fs */
+       kill_fasync(&fc->fasync, SIGIO, POLL_IN);
        wake_up_all(&fc->waitq);
        kobject_del(&fc->kobj);
        kobject_put(&fc->kobj);