Commit 3393ff96 authored Jan 20, 2025 by Bernd Schubert Committed by Miklos Szeredi Jan 27, 2025

fuse: block request allocation until io-uring init is complete



Avoid races and block request allocation until io-uring
queues are ready.

This is a especially important for background requests,
as bg request completion might cause lock order inversion
of the typical queue->lock and then fc->bg_lock

    fuse_request_end
       spin_lock(&fc->bg_lock);
       flush_bg_queue
         fuse_send_one
           fuse_uring_queue_fuse_req
           spin_lock(&queue->lock);

Signed-off-by: Bernd Schubert <bernd@bsbernd.com>
Reviewed-by: Luis Henriques <luis@igalia.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent b6236c84

fs/fuse/dev.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -76,7 +76,8 @@ void fuse_set_initialized(struct fuse_conn *fc)

		static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
		{
		return !fc->initialized \|\| (for_background && fc->blocked);
		return !fc->initialized \|\| (for_background && fc->blocked) \|\|
		(fc->io_uring && !fuse_uring_ready(fc));
		}

		static void fuse_drop_waiting(struct fuse_conn *fc)

fs/fuse/dev_uring.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -957,6 +957,7 @@ static void fuse_uring_do_register(struct fuse_ring_ent *ent,
		if (ready) {
		WRITE_ONCE(fiq->ops, &fuse_io_uring_ops);
		WRITE_ONCE(ring->ready, true);
		wake_up_all(&fc->blocked_waitq);
		}
		}
		}
		@@ -1130,6 +1131,8 @@ int __maybe_unused fuse_uring_cmd(struct io_uring_cmd *cmd,
		if (err) {
		pr_info_once("FUSE_IO_URING_CMD_REGISTER failed err=%d\n",
		err);
		fc->io_uring = 0;
		wake_up_all(&fc->blocked_waitq);
		return err;
		}
		break;

fs/fuse/fuse_i.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -867,6 +867,9 @@ struct fuse_conn {
		/* Use pages instead of pointer for kernel I/O */
		unsigned int use_pages_for_kvec_io:1;

		/* Use io_uring for communication */
		unsigned int io_uring;

		/** Maximum stack depth for passthrough backing files */
		int max_stack_depth;

fs/fuse/inode.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1390,6 +1390,8 @@ static void process_init_reply(struct fuse_mount fm, struct fuse_args args,
		else
		ok = false;
		}
		if (flags & FUSE_OVER_IO_URING && fuse_uring_enabled())
		fc->io_uring = 1;
		} else {
		ra_pages = fc->max_read / PAGE_SIZE;
		fc->no_lock = 1;