[PATCH] md: don't print the same repeated messages about delayed sync operation

[PATCH] md: don't print the same repeated messages about delayed sync operation

[Artur Paszkiewicz]

This fixes a long-standing bug that caused a flood of messages like:
"md: delaying data-check of md1 until md2 has finished (they share one
or more physical units)"

It can be reproduced like this:
1. Create at least 3 raid1 arrays on a pair of disks, each on different
   partitions.
2. Request a sync operation like 'check' or 'repair' on 2 arrays by
   writing to their md/sync_action attribute files. One operation should
   start and one should be delayed and a message like the above will be
   printed.
3. Issue a write to the third array. Each write will cause 2 copies of
   the message to be printed.

This happens when wake_up(&resync_wait) is called, usually by
md_check_recovery(). Then the delayed sync thread again prints the
message and is put to sleep. This patch adds a check in md_do_sync() to
prevent printing this message more than once for the same pair of
devices.

Reported-by: Sven Koehler <sven.koehler@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=151801
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
---
 drivers/md/md.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2c3ab6f..5096b48 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7862,6 +7862,7 @@ void md_do_sync(struct md_thread *thread)
 	 */
 
 	do {
+		int mddev2_minor = -1;
 		mddev->curr_resync = 2;
 
 	try_again:
@@ -7891,10 +7892,14 @@ void md_do_sync(struct md_thread *thread)
 				prepare_to_wait(&resync_wait, &wq, TASK_INTERRUPTIBLE);
 				if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
 				    mddev2->curr_resync >= mddev->curr_resync) {
-					printk(KERN_INFO "md: delaying %s of %s"
-					       " until %s has finished (they"
-					       " share one or more physical units)\n",
-					       desc, mdname(mddev), mdname(mddev2));
+					if (mddev2_minor != mddev2->md_minor) {
+						mddev2_minor = mddev2->md_minor;
+						printk(KERN_INFO "md: delaying %s of %s"
+						       " until %s has finished (they"
+						       " share one or more physical units)\n",
+						       desc, mdname(mddev),
+						       mdname(mddev2));
+					}
 					mddev_put(mddev2);
 					if (signal_pending(current))
 						flush_signals(current);
-- 
2.9.2

Re: [PATCH] md: don't print the same repeated messages about delayed sync operation

[Shaohua Li]

On Tue, Aug 16, 2016 at 02:26:08PM +0200, Artur Paszkiewicz wrote:
> This fixes a long-standing bug that caused a flood of messages like:
> "md: delaying data-check of md1 until md2 has finished (they share one
> or more physical units)"
> 
> It can be reproduced like this:
> 1. Create at least 3 raid1 arrays on a pair of disks, each on different
>    partitions.
> 2. Request a sync operation like 'check' or 'repair' on 2 arrays by
>    writing to their md/sync_action attribute files. One operation should
>    start and one should be delayed and a message like the above will be
>    printed.
> 3. Issue a write to the third array. Each write will cause 2 copies of
>    the message to be printed.
> 
> This happens when wake_up(&resync_wait) is called, usually by
> md_check_recovery(). Then the delayed sync thread again prints the
> message and is put to sleep. This patch adds a check in md_do_sync() to
> prevent printing this message more than once for the same pair of
> devices.
> 
> Reported-by: Sven Koehler <sven.koehler@gmail.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=151801
> Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
> ---
>  drivers/md/md.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 2c3ab6f..5096b48 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -7862,6 +7862,7 @@ void md_do_sync(struct md_thread *thread)
>  	 */
>  
>  	do {
> +		int mddev2_minor = -1;
>  		mddev->curr_resync = 2;
>  
>  	try_again:
> @@ -7891,10 +7892,14 @@ void md_do_sync(struct md_thread *thread)
>  				prepare_to_wait(&resync_wait, &wq, TASK_INTERRUPTIBLE);
>  				if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
>  				    mddev2->curr_resync >= mddev->curr_resync) {
> -					printk(KERN_INFO "md: delaying %s of %s"
> -					       " until %s has finished (they"
> -					       " share one or more physical units)\n",
> -					       desc, mdname(mddev), mdname(mddev2));
> +					if (mddev2_minor != mddev2->md_minor) {
> +						mddev2_minor = mddev2->md_minor;
> +						printk(KERN_INFO "md: delaying %s of %s"
> +						       " until %s has finished (they"
> +						       " share one or more physical units)\n",
> +						       desc, mdname(mddev),
> +						       mdname(mddev2));
> +					}
>  					mddev_put(mddev2);
>  					if (signal_pending(current))
>  						flush_signals(current);

applied, thanks!