[dm-devel] Patch "dm mpath: only use ktime_get_ns() in historical selector" has been added to the 5.15-stable tree

[dm-devel] Patch "dm mpath: only use ktime_get_ns() in historical selector" has been added to the 5.15-stable tree

[Sasha Levin]

This is a note to let you know that I've just added the patch titled

    dm mpath: only use ktime_get_ns() in historical selector

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-mpath-only-use-ktime_get_ns-in-historical-selecto.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.



commit d944a5392b422a0721a00dfd87de491045451b79
Author: Khazhismel Kumykov <khazhy@google.com>
Date:   Mon Apr 11 15:03:35 2022 -0700

    dm mpath: only use ktime_get_ns() in historical selector
    
    [ Upstream commit ce40426fdc3c92acdba6b5ca74bc7277ffaa6a3d ]
    
    Mixing sched_clock() and ktime_get_ns() usage will give bad results.
    
    Switch hst_select_path() from using sched_clock() to ktime_get_ns().
    Also rename path_service_time()'s 'sched_now' variable to 'now'.
    
    Fixes: 2613eab11996 ("dm mpath: add Historical Service Time Path Selector")
    Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
    Signed-off-by: Mike Snitzer <snitzer@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/dm-ps-historical-service-time.c b/drivers/md/dm-ps-historical-service-time.c
index 1856a1b125cc..82f2a06153dc 100644
--- a/drivers/md/dm-ps-historical-service-time.c
+++ b/drivers/md/dm-ps-historical-service-time.c
@@ -432,7 +432,7 @@ static struct dm_path *hst_select_path(struct path_selector *ps,
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = NULL, *best = NULL;
-	u64 time_now = sched_clock();
+	u64 time_now = ktime_get_ns();
 	struct dm_path *ret = NULL;
 	unsigned long flags;
 
@@ -473,7 +473,7 @@ static int hst_start_io(struct path_selector *ps, struct dm_path *path,
 
 static u64 path_service_time(struct path_info *pi, u64 start_time)
 {
-	u64 sched_now = ktime_get_ns();
+	u64 now = ktime_get_ns();
 
 	/* if a previous disk request has finished after this IO was
 	 * sent to the hardware, pretend the submission happened
@@ -482,11 +482,11 @@ static u64 path_service_time(struct path_info *pi, u64 start_time)
 	if (time_after64(pi->last_finish, start_time))
 		start_time = pi->last_finish;
 
-	pi->last_finish = sched_now;
-	if (time_before64(sched_now, start_time))
+	pi->last_finish = now;
+	if (time_before64(now, start_time))
 		return 0;
 
-	return sched_now - start_time;
+	return now - start_time;
 }
 
 static int hst_end_io(struct path_selector *ps, struct dm_path *path,

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