Re: [PATCH] ext4: add sysfs attr /sys/fs/ext4/<disk>/journal_task

[Theodore Y. Ts'o]

On Mon, Feb 04, 2019 at 01:17:43PM +0300, Konstantin Khlebnikov wrote:
> This is useful for moving journal thread into cgroup or
> for tracing it with ftrace/perf/blktrace.
> 
> For now the only way is `pgrep jbd2/$DISK` but this is not reliable:
> name may be longer than "comm" limit and any task could mock it.
> 
> Attribute shows pid in current pid-namespace or 0 if task is unreachable.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>

Thanks, applied with one change; if the file system does not have a
journal, reading the /sys/fs/ext4/<disk>/journal_task will return
"<none>" instead of returning a ESRCH error.

	 	    	      	      - Ted