Commit 3421c7f6 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

ublk: make sure io cmd handled in submitter task context 



In well-done ublk server implementation, ublk io command won't be
linked into any link chain. Meantime they are always handled in no-wait
style, so basically io cmd is always handled in submitter task context.

However, the server may set IOSQE_ASYNC, or io command is linked to one
chain mistakenly, then we may still run into io-wq context and
ctx->uring_lock isn't held.

So in case of IO_URING_F_UNLOCKED, schedule this command by
io_uring_cmd_complete_in_task to force running it in submitter task. Then
ublk_ch_uring_cmd_local() is guaranteed to run with context uring_lock held,
and we needn't to worry about sync among submission code path any more.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20231009093324.957829-3-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8ed90e37

drivers/block/ublk_drv.c

+21 −1
Original line number Diff line number Diff line
@@ -1811,7 +1811,8 @@ static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub, 
	return NULL;

}



static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)

static inline int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,

		unsigned int issue_flags)

{

	/*

	 * Not necessary for async retry, but let's keep it simple and always
@@ -1825,9 +1826,28 @@ static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags) 
		.addr = READ_ONCE(ub_src->addr)

	};



	WARN_ON_ONCE(issue_flags & IO_URING_F_UNLOCKED);



	return __ublk_ch_uring_cmd(cmd, issue_flags, &ub_cmd);

}



static void ublk_ch_uring_cmd_cb(struct io_uring_cmd *cmd,

		unsigned int issue_flags)

{

	ublk_ch_uring_cmd_local(cmd, issue_flags);

}



static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)

{

	/* well-implemented server won't run into unlocked */

	if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {

		io_uring_cmd_complete_in_task(cmd, ublk_ch_uring_cmd_cb);

		return -EIOCBQUEUED;

	}



	return ublk_ch_uring_cmd_local(cmd, issue_flags);

}



static inline bool ublk_check_ubuf_dir(const struct request *req,

		int ubuf_dir)

{