Messages in this thread Patch in this message | | | Date | Mon, 27 Feb 2006 13:37:59 -0500 | From | Jeff Dike <> | Subject | [PATCH] Add O_ASYNC support to FUSE |
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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, unlike 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 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.
One possible bug - there is a wakeup in inode.c:fuse_put_super, but sticking a kill_fasync there causes BUGs because the /dev/fuse file struct seems to have gone away. So, this may be lacking when a FUSE mount is unmounted from underneath the server (is that possible, or must the server be killed in order to do the umount?).
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Index: host-2.6.15-fuse/fs/fuse/dev.c =================================================================== --- host-2.6.15-fuse.orig/fs/fuse/dev.c 2006-02-18 12:19:07.000000000 -0500 +++ host-2.6.15-fuse/fs/fuse/dev.c 2006-02-27 13:19:10.000000000 -0500 @@ -311,6 +311,7 @@ static void queue_request(struct fuse_co list_add_tail(&req->list, &fc->pending); req->state = FUSE_REQ_PENDING; wake_up(&fc->waitq); + kill_fasync(&fc->fasync, SIGIO, POLL_IN); } /* @@ -894,6 +895,7 @@ void fuse_abort_conn(struct fuse_conn *f end_requests(fc, &fc->pending); end_requests(fc, &fc->processing); wake_up_all(&fc->waitq); + kill_fasync(&fc->fasync, SIGIO, POLLIN); } spin_unlock(&fuse_lock); } @@ -913,9 +915,20 @@ static int fuse_dev_release(struct inode if (fc) kobject_put(&fc->kobj); + 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; + + /* No locking - fasync_helper does its own locking */ + fc = file->private_data; + return(fasync_helper(fd, file, on, &fc->fasync)); +} + struct file_operations fuse_dev_operations = { .owner = THIS_MODULE, .llseek = no_llseek, @@ -925,6 +938,7 @@ struct file_operations fuse_dev_operatio .writev = fuse_dev_writev, .poll = fuse_dev_poll, .release = fuse_dev_release, + .fasync = fuse_dev_fasync, }; static struct miscdevice fuse_miscdevice = { Index: host-2.6.15-fuse/fs/fuse/fuse_i.h =================================================================== --- host-2.6.15-fuse.orig/fs/fuse/fuse_i.h 2006-02-24 17:46:47.000000000 -0500 +++ host-2.6.15-fuse/fs/fuse/fuse_i.h 2006-02-24 18:24:49.000000000 -0500 @@ -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) Index: host-2.6.15-fuse/fs/fuse/inode.c =================================================================== --- host-2.6.15-fuse.orig/fs/fuse/inode.c 2006-02-18 12:19:07.000000000 -0500 +++ host-2.6.15-fuse/fs/fuse/inode.c 2006-02-27 13:17:50.000000000 -0500 @@ -17,6 +17,7 @@ #include <linux/module.h> #include <linux/parser.h> #include <linux/statfs.h> +#include <linux/poll.h> MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); MODULE_DESCRIPTION("Filesystem in Userspace"); @@ -377,6 +378,7 @@ static void fuse_conn_release(struct kob list_del(&req->list); fuse_request_free(req); } + kfree(fc); } @@ -409,6 +411,7 @@ static struct fuse_conn *new_conn(void) fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; fc->bdi.unplug_io_fn = default_unplug_io_fn; fc->reqctr = 0; + fc->fasync = NULL; } return fc; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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