SIGIO-driven I/O with inotify queues

Add SIGIO-driven I/O for descriptors returned by inotify_init().  The thing
may be enabled by convenient fcntl (fd, F_SETFL, O_ASYNC) call.

Signed-off-by: Dmitry Antipov <antipov@dev.rtsoft.ru>
Cc: Robert Love <rlove@google.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/inotify_user.c b/fs/inotify_user.c
index c509a817068f86d97eba002c4a64e4cf93bb43ef..a336c9709f3cc477ed15236642b743f0a3ca493e 100644 (file)
--- a/fs/inotify_user.c
+++ b/fs/inotify_user.c
@@ -79,6 +79,7 @@ struct inotify_device {
        atomic_t                count;          /* reference count */
        struct user_struct      *user;          /* user who opened this dev */
        struct inotify_handle   *ih;            /* inotify handle */
+       struct fasync_struct    *fa;            /* async notification */
        unsigned int            queue_size;     /* size of the queue (bytes) */
        unsigned int            event_count;    /* number of pending events */
        unsigned int            max_events;     /* maximum number of events */
@@ -315,6 +316,7 @@ static void inotify_dev_queue_event(struct inotify_watch *w, u32 wd, u32 mask,
        dev->queue_size += sizeof(struct inotify_event) + kevent->event.len;
        list_add_tail(&kevent->list, &dev->events);
        wake_up_interruptible(&dev->wq);
+       kill_fasync(&dev->fa, SIGIO, POLL_IN);
 
 out:
        mutex_unlock(&dev->ev_mutex);
@@ -503,6 +505,13 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
        return ret;
 }
 
+static int inotify_fasync(int fd, struct file *file, int on)
+{
+       struct inotify_device *dev = file->private_data;
+
+       return fasync_helper(fd, file, on, &dev->fa) >= 0 ? 0 : -EIO;
+}
+
 static int inotify_release(struct inode *ignored, struct file *file)
 {
        struct inotify_device *dev = file->private_data;
@@ -515,6 +524,9 @@ static int inotify_release(struct inode *ignored, struct file *file)
                inotify_dev_event_dequeue(dev);
        mutex_unlock(&dev->ev_mutex);
 
+       if (file->f_flags & FASYNC)
+               inotify_fasync(-1, file, 0);
+
        /* free this device: the put matching the get in inotify_init() */
        put_inotify_dev(dev);
 
@@ -543,6 +555,7 @@ static long inotify_ioctl(struct file *file, unsigned int cmd,
 static const struct file_operations inotify_fops = {
        .poll           = inotify_poll,
        .read           = inotify_read,
+       .fasync         = inotify_fasync,
        .release        = inotify_release,
        .unlocked_ioctl = inotify_ioctl,
        .compat_ioctl   = inotify_ioctl,
@@ -590,6 +603,7 @@ asmlinkage long sys_inotify_init(void)
                goto out_free_dev;
        }
        dev->ih = ih;
+       dev->fa = NULL;
 
        filp->f_op = &inotify_fops;
        filp->f_path.mnt = mntget(inotify_mnt);