Bug 1818912

Same behaviour on Fedora 31:
kernel-5.5.10-200.fc31.x86_64
mdadm-4.1-4.fc31.x86_64

# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid6 loop3[4] loop2[3] loop1[1] loop0[0]
      2093056 blocks super 1.2 level 6, 512k chunk, algorithm 18 [4/3] [UUU_]
      [>....................]  reshape =  0.0% (1/1046528) finish=0.0min speed=174421K/sec
      
unused devices: <none>



And on Fedora 32:
kernel-5.6.0-0.rc7.git0.2.fc32.x86_64
mdadm-4.1-4.fc32.x86_64

# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid6 loop3[4] loop2[3] loop1[1] loop0[0]
      2093056 blocks super 1.2 level 6, 512k chunk, algorithm 18 [4/3] [UUU_]
      [>....................]  reshape =  0.0% (1/1046528) finish=0.0min speed=174421K/sec
      
unused devices: <none>

https://www.spinics.net/lists/raid/msg64347.html

https://marc.info/?l=linux-raid&m=159195299630680&w=2

Verified the above patch fixes the hang and allows the grow to proceed.

My mistake, it does not fix it.

On fedora32, running the posted reproducer script...

I see no progress with two threads, md0_raid6, md0_reshape.

# ps aux |grep md0
root        1265  0.0  0.0      0     0 ?        S    10:43   0:00 [md0_raid6]
root        1271  0.0  0.0      0     0 ?        S    10:43   0:00 [md0_reshape]
root        1274  0.0  0.0   5668  4804 ?        SLs  10:43   0:00 /usr/sbin/mdadm --grow --continue /dev/md0
root        1312  0.0  0.0 216084   644 pts/0    S+   10:59   0:00 grep --color=auto md0


what could be minutes or hours later... no progress
# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid6 loop3[4] loop2[3] loop1[1] loop0[0]
      2093056 blocks super 1.2 level 6, 512k chunk, algorithm 18 [4/3] [UUU_]
      [>....................]  reshape =  1.5% (16384/1046528) finish=1091.8min speed=15K/sec
      
unused devices: <none>

Jes, if you want to review... I'll post upstream..


diff --git a/Grow.c b/Grow.c
index 6b8321c..66bd8c0 100644
--- a/Grow.c
+++ b/Grow.c
@@ -931,10 +931,13 @@ int start_reshape(struct mdinfo *sra, int already_running,
        err = err ?: sysfs_set_num(sra, NULL, "sync_max", sync_max_to_set);
        if (!already_running && err == 0) {
                int cnt = 5;
+               int err2;
                do {
                        err = sysfs_set_str(sra, NULL, "sync_action",
                                            "reshape");
-                       if (err)
+                       err2 = sysfs_set_str(sra, NULL, "sync_max",
+                                           "max");
+                       if (err || err2)
                                sleep(1);
                } while (err && errno == EBUSY && cnt-- > 0);
        }

(In reply to Nigel Croxon from comment #6)
> -                       if (err)
> +                       err2 = sysfs_set_str(sra, NULL, "sync_max",
> +                                           "max");
> +                       if (err || err2)
>                                 sleep(1);
>                 } while (err && errno == EBUSY && cnt-- > 0);
>         }

shouldn't `err2` be added to `while (...`?

Yes, thanks Hubert.

[root@mdbox mdadm]# git diff Grow.c
diff --git a/Grow.c b/Grow.c
index 57db7d4..8e4391f 100644
--- a/Grow.c
+++ b/Grow.c
@@ -931,12 +931,15 @@ int start_reshape(struct mdinfo *sra, int already_running,
        err = err ?: sysfs_set_num(sra, NULL, "sync_max", sync_max_to_set);
        if (!already_running && err == 0) {
                int cnt = 5;
+               int err2;
                do {
                        err = sysfs_set_str(sra, NULL, "sync_action",
                                            "reshape");
-                       if (err)
+                       err2 = sysfs_set_str(sra, NULL, "sync_max",
+                                           "max");
+                       if (err || err2)
                                sleep(1);
-               } while (err && errno == EBUSY && cnt-- > 0);
+               } while (err && err2 && errno == EBUSY && cnt-- > 0);
        }
        return err;
 }

https://www.spinics.net/lists/raid/msg67053.html

Hello Jes,

Do you have a status on the upstream patch that was submitted?


Thanks for your time,
-Nigel

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