Re: [PATCH] md: use TASK_IDLE instead of blocking signals

[NeilBrown <neilb@suse.com>]

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On Wed, Oct 18 2017, Mikulas Patocka wrote:

> Hi - I submit this patch for the next merge window:
>
>
> Some times ago, I made a patch f9c79bc05a2a that blocks signals around the
> schedule() calls in MD. The MD subsystem needs to do an uninterruptible
> sleep that is not accounted in load average - so we block signals and use
> interruptible sleep.
>
> The kernel has a special TASK_IDLE state for this purpose, so we can use
> it instead of blocking signals. This patch doesn't fix any bug, it just
> makes the code simpler.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Thanks for doing this!  It has been on my mind to look at exactly this
possibility for a while but it never quite happened.  Now I don't need
to :-)

Acked-by: NeilBrown <neilb@suse.com>

Thanks,
NeilBrown


>
> ---
>  drivers/md/raid1.c |    7 +------
>  drivers/md/raid5.c |    7 +------
>  2 files changed, 2 insertions(+), 12 deletions(-)
>
> Index: linux-2.6/drivers/md/raid1.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/raid1.c
> +++ linux-2.6/drivers/md/raid1.c
> @@ -37,7 +37,6 @@
>  #include <linux/module.h>
>  #include <linux/seq_file.h>
>  #include <linux/ratelimit.h>
> -#include <linux/sched/signal.h>
>  
>  #include <trace/events/block.h>
>  
> @@ -1322,9 +1321,8 @@ static void raid1_write_request(struct m
>  		 */
>  		DEFINE_WAIT(w);
>  		for (;;) {
> -			sigset_t full, old;
>  			prepare_to_wait(&conf->wait_barrier,
> -					&w, TASK_INTERRUPTIBLE);
> +					&w, TASK_IDLE);
>  			if (bio_end_sector(bio) <= mddev->suspend_lo ||
>  			    bio->bi_iter.bi_sector >= mddev->suspend_hi ||
>  			    (mddev_is_clustered(mddev) &&
> @@ -1332,10 +1330,7 @@ static void raid1_write_request(struct m
>  				     bio->bi_iter.bi_sector,
>  				     bio_end_sector(bio))))
>  				break;
> -			sigfillset(&full);
> -			sigprocmask(SIG_BLOCK, &full, &old);
>  			schedule();
> -			sigprocmask(SIG_SETMASK, &old, NULL);
>  		}
>  		finish_wait(&conf->wait_barrier, &w);
>  	}
> Index: linux-2.6/drivers/md/raid5.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/raid5.c
> +++ linux-2.6/drivers/md/raid5.c
> @@ -55,7 +55,6 @@
>  #include <linux/ratelimit.h>
>  #include <linux/nodemask.h>
>  #include <linux/flex_array.h>
> -#include <linux/sched/signal.h>
>  
>  #include <trace/events/block.h>
>  #include <linux/list_sort.h>
> @@ -5691,14 +5690,10 @@ static bool raid5_make_request(struct md
>  				 * wait.
>  				 */
>  				prepare_to_wait(&conf->wait_for_overlap,
> -						&w, TASK_INTERRUPTIBLE);
> +						&w, TASK_IDLE);
>  				if (logical_sector >= mddev->suspend_lo &&
>  				    logical_sector < mddev->suspend_hi) {
> -					sigset_t full, old;
> -					sigfillset(&full);
> -					sigprocmask(SIG_BLOCK, &full, &old);
>  					schedule();
> -					sigprocmask(SIG_SETMASK, &old, NULL);
>  					do_prepare = true;
>  				}
>  				goto retry;

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