Commit 385a17bf authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
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[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

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: default avatarJeff Dike <>
Signed-off-by: default avatarMiklos Szeredi <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 7025d9ad
......@@ -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;
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);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
......@@ -917,12 +919,24 @@ static int fuse_dev_release(struct inode *inode, struct file *file)
end_requests(fc, &fc->processing);
if (fc)
if (fc) {
fasync_helper(-1, file, 0, &fc->fasync);
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 = {
......@@ -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)
......@@ -216,6 +216,7 @@ static void fuse_put_super(struct super_block *sb)
/* Flush all readers on this fs */
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
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