On Mon, Apr 10, 2017 at 11:40:49AM -0700, Bart Van Assche wrote:
> On 04/10/2017 11:28 AM, Jens Axboe wrote:
> > On 03/30/2017 12:21 PM, Bart Van Assche wrote:
> >> This is a short patch series with one patch that exports the queue state
> >> and another patch that shows symbolic names for hctx state and flags
> >> instead of a numerical bitmask.
> >>
> >> Please consider these patches for kernel v4.12.
> >
> > Thanks, added for 4.12.
>
> Hello Jens,
>
> Thanks! This infrastructure was essential while analyzing queue stalls.
>
> After I had posted this series I improved and extended the blk-mq debugfs
> functionality further. Please consider including the patch below in v4.12.
>
> Thanks,
>
> Bart.
>
>
> From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> Subject: [PATCH] blk-mq: Two fixes for the code that exports the queue state
>
> Remove the array entry for QUEUE_FLAG_RESTART since that flag has
> been removed after the blk-mq-debugfs patch that introduced this
> array entry was posted.
>
> Avoid that querying the queue state of a dead queue triggers a
> kernel crash.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> ---
> block/blk-mq-debugfs.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
> index 91d09f58a596..a1ce823578c7 100644
> --- a/block/blk-mq-debugfs.c
> +++ b/block/blk-mq-debugfs.c
> @@ -92,7 +92,6 @@ static const char *const blk_queue_flag_name[] = {
> [QUEUE_FLAG_FLUSH_NQ] = "FLUSH_NQ",
> [QUEUE_FLAG_DAX] = "DAX",
> [QUEUE_FLAG_STATS] = "STATS",
> - [QUEUE_FLAG_RESTART] = "RESTART",
> [QUEUE_FLAG_POLL_STATS] = "POLL_STATS",
> [QUEUE_FLAG_REGISTERED] = "REGISTERED",
> };
> @@ -112,6 +111,14 @@ static ssize_t blk_queue_flags_store(struct file *file, const char __user *ubuf,
> struct request_queue *q = file_inode(file)->i_private;
> char op[16] = { }, *s;
>
> + /*
> + * The debugfs attributes are removed after blk_cleanup_queue() has
> + * called blk_mq_free_queue(). Return if QUEUE_FLAG_DEAD has been set
> + * to avoid triggering a use-after-free.
> + */
> + if (blk_queue_dead(q))
> + return -ENOENT;
> +
Can you just move blk_queue_flags_fops to blk_mq_debugfs_queue_attrs
instead of adding blk_queue_attrs?
