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Re: [dm-devel] dm-raid1 barriers



> > If this flush fails, the bits in memory are already clean and we don't 
> > know which regions may hold unwritten data in the disk cache and which 
> 
> Actually we do: the on-disk version of the log tells us.

Yes, it could be read into another buffer and anded.

> > not. So, we must set all regions as dirty.
>  
> Anyway, let's not try to handle these situations at the moment.
> what I need for now, is a way to know whether or not this situation has
> actually occurred when we get reports from users, so probably a kernel
> log message, a dm event raised plus a failure indicator against the device in
> the status line.
> 
> Alasdair

Here I'm attaching two patches that make it report 'F' on flush error. But 
I think it's not really important, the flush error could be treated as 
write error, there is no need for special handling of flush errors --- 
both flush errors and write errors can happen either on transport errors 
or if the device is out of spare sectors.

Note that this approach of reporting flushes speciall also breaks 
new-kernel-with-old-userspace case.

Mikulas
Report flush errors as 'F' instead of 'D' for log and mirror devices.

Signed-off-by: Mikulas Patocka <mpatocka redhat com>

---
 drivers/md/dm-log.c   |   16 ++++++++++++----
 drivers/md/dm-raid1.c |    6 ++++--
 2 files changed, 16 insertions(+), 6 deletions(-)

Index: linux-2.6.31.6-fast/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.31.6-fast.orig/drivers/md/dm-raid1.c	2009-11-17 09:08:15.000000000 +0100
+++ linux-2.6.31.6-fast/drivers/md/dm-raid1.c	2009-11-17 09:10:07.000000000 +0100
@@ -35,6 +35,7 @@ static DECLARE_WAIT_QUEUE_HEAD(_kmirrord
  *---------------------------------------------------------------*/
 enum dm_raid1_error {
 	DM_RAID1_WRITE_ERROR,
+	DM_RAID1_FLUSH_ERROR,
 	DM_RAID1_SYNC_ERROR,
 	DM_RAID1_READ_ERROR
 };
@@ -270,7 +271,7 @@ static int mirror_flush(void *ms_)
 	if (unlikely(error_bits != 0)) {
 		for (i = 0; i < ms->nr_mirrors; i++)
 			if (test_bit(i, &error_bits))
-				fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
+				fail_mirror(ms->mirror + i, DM_RAID1_FLUSH_ERROR);
 		return -EIO;
 	}
 
@@ -1312,7 +1313,8 @@ static char device_status_char(struct mi
 	if (!atomic_read(&(m->error_count)))
 		return 'A';
 
-	return (test_bit(DM_RAID1_WRITE_ERROR, &(m->error_type))) ? 'D' :
+	return (test_bit(DM_RAID1_FLUSH_ERROR, &(m->error_type))) ? 'F' :
+		(test_bit(DM_RAID1_WRITE_ERROR, &(m->error_type))) ? 'D' :
 		(test_bit(DM_RAID1_SYNC_ERROR, &(m->error_type))) ? 'S' :
 		(test_bit(DM_RAID1_READ_ERROR, &(m->error_type))) ? 'R' : 'U';
 }
Index: linux-2.6.31.6-fast/drivers/md/dm-log.c
===================================================================
--- linux-2.6.31.6-fast.orig/drivers/md/dm-log.c	2009-11-17 10:20:39.000000000 +0100
+++ linux-2.6.31.6-fast/drivers/md/dm-log.c	2009-11-17 10:22:17.000000000 +0100
@@ -235,6 +235,7 @@ struct log_c {
 	 * Disk log fields
 	 */
 	int log_dev_failed;
+	int log_dev_flush_failed;
 	struct dm_dev *log_dev;
 	struct log_header header;
 
@@ -422,6 +423,7 @@ static int create_log_context(struct dm_
 	} else {
 		lc->log_dev = dev;
 		lc->log_dev_failed = 0;
+		lc->log_dev_flush_failed = 0;
 		lc->header_location.bdev = lc->log_dev->bdev;
 		lc->header_location.sector = 0;
 
@@ -630,8 +632,11 @@ static int disk_resume(struct dm_dirty_l
 
 	/* write the new header */
 	r = rw_header(lc, WRITE);
-	if (!r)
+	if (!r) {
 		r = flush_header(lc);
+		if (r)
+			lc->log_dev_flush_failed = 1;
+	}
 	if (r) {
 		DMWARN("%s: Failed to write header on dirty region log device",
 		       lc->log_dev->name);
@@ -701,9 +706,10 @@ static int disk_flush(struct dm_dirty_lo
 	else {
 		if (lc->touched_dirtied) {
 			r = flush_header(lc);
-			if (r)
+			if (r) {
+				lc->log_dev_flush_failed = 1;
 				fail_log_device(lc);
-			else
+			} else
 				lc->touched_dirtied = 0;
 		}
 		lc->touched_cleaned = 0;
@@ -803,7 +809,9 @@ static int disk_status(struct dm_dirty_l
 	switch(status) {
 	case STATUSTYPE_INFO:
 		DMEMIT("3 %s %s %c", log->type->name, lc->log_dev->name,
-		       lc->log_dev_failed ? 'D' : 'A');
+		       lc->log_dev_flush_failed ? 'F' :
+		       lc->log_dev_failed ? 'D' :
+		       'A');
 		break;
 
 	case STATUSTYPE_TABLE:
Accept 'F' for devices with failed flush.

Signed-off-by: Mikulas Patocka <mpatocka redhat com>

---
 daemons/dmeventd/plugins/mirror/dmeventd_mirror.c |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

Index: LVM2.2.02.54/daemons/dmeventd/plugins/mirror/dmeventd_mirror.c
===================================================================
--- LVM2.2.02.54.orig/daemons/dmeventd/plugins/mirror/dmeventd_mirror.c	2009-11-17 09:12:40.000000000 +0100
+++ LVM2.2.02.54/daemons/dmeventd/plugins/mirror/dmeventd_mirror.c	2009-11-17 10:56:43.000000000 +0100
@@ -94,12 +94,23 @@ static int _get_mirror_event(char *param
 			syslog(LOG_ERR, "Mirror device, %s, has failed.\n", args[i]);
 			r = ME_FAILURE;
 		}
+		if (dev_status_str[i] == 'F') {
+			syslog(LOG_ERR, "Flush on mirror device, %s, has failed.\n", args[i]);
+			r = ME_FAILURE;
+		}
 
 	/* Check for bad disk log device */
-	if (log_argc > 1 && log_status_str[0] == 'D') {
-		syslog(LOG_ERR, "Log device, %s, has failed.\n",
-		       args[2 + num_devs + log_argc]);
-		r = ME_FAILURE;
+	if (log_argc > 1) {
+		if (log_status_str[0] == 'D') {
+			syslog(LOG_ERR, "Log device, %s, has failed.\n",
+			       args[2 + num_devs + log_argc]);
+			r = ME_FAILURE;
+		}
+		if (log_status_str[0] == 'F') {
+			syslog(LOG_ERR, "Flush on log device, %s, has failed.\n",
+			       args[2 + num_devs + log_argc]);
+			r = ME_FAILURE;
+		}
 	}
 
 	if (r == ME_FAILURE)

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