md: md: raid5 rate limit error printk

Last night we had scsi problems and a hardware raid unit was offlined
during heavy i/o.  While this happened we got for about 3 minutes a huge
number messages like these

Apr 12 03:36:07 pfs1n14 kernel: [197510.696595] raid5:md7: read error not correctable (sector 2993096568 on sdj2).

I guess the high error rate is responsible for not scheduling other events
- during this time the system was not pingable and in the end also other
devices run into scsi command timeouts causing problems on these unrelated
devices as well.
Signed-off-by: Bernd Schubert <bernd-schubert@gmx.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/raid5.c

@@ -94,6 +94,8 @@
 #define __inline__
 #endif
 
+#define printk_rl(args...) ((void) (printk_ratelimit() && printk(args)))
+
 #if !RAID6_USE_EMPTY_ZERO_PAGE
 /* In .bss so it's zeroed */
 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
@@ -1143,10 +1145,12 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		set_bit(R5_UPTODATE, &sh->dev[i].flags);
 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
 			rdev = conf->disks[i].rdev;
-			printk(KERN_INFO "raid5:%s: read error corrected (%lu sectors at %llu on %s)\n",
-			       mdname(conf->mddev), STRIPE_SECTORS,
-			       (unsigned long long)(sh->sector + rdev->data_offset),
-			       bdevname(rdev->bdev, b));
+			printk_rl(KERN_INFO "raid5:%s: read error corrected"
+				  " (%lu sectors at %llu on %s)\n",
+				  mdname(conf->mddev), STRIPE_SECTORS,
+				  (unsigned long long)(sh->sector
+						       + rdev->data_offset),
+				  bdevname(rdev->bdev, b));
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
 		}
@@ -1160,16 +1164,22 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
 		atomic_inc(&rdev->read_errors);
 		if (conf->mddev->degraded)
-			printk(KERN_WARNING "raid5:%s: read error not correctable (sector %llu on %s).\n",
-			       mdname(conf->mddev),
-			       (unsigned long long)(sh->sector + rdev->data_offset),
-			       bdn);
+			printk_rl(KERN_WARNING
+				  "raid5:%s: read error not correctable "
+				  "(sector %llu on %s).\n",
+				  mdname(conf->mddev),
+				  (unsigned long long)(sh->sector
+						       + rdev->data_offset),
+				  bdn);
 		else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
 			/* Oh, no!!! */
-			printk(KERN_WARNING "raid5:%s: read error NOT corrected!! (sector %llu on %s).\n",
-			       mdname(conf->mddev),
-			       (unsigned long long)(sh->sector + rdev->data_offset),
-			       bdn);
+			printk_rl(KERN_WARNING
+				  "raid5:%s: read error NOT corrected!! "
+				  "(sector %llu on %s).\n",
+				  mdname(conf->mddev),
+				  (unsigned long long)(sh->sector
+						       + rdev->data_offset),
+				  bdn);
 		else if (atomic_read(&rdev->read_errors)
 			 > conf->max_nr_stripes)
 			printk(KERN_WARNING