On 07/06/2015 04:12 AM, Hannes Reinecke wrote:
During ALUA state transitions the device might return
a sense code 02/04/0a (Logical unit not accessible, asymmetric
access state transition). As this is a transient error
we should just retry the READ CAPACITY call after 1 second
until the state transition finishes and the correct
capacity can be returned.
At the same time we should break out of the loop after
2 minutes to avoid unbounded retries.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
drivers/scsi/sd.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3b2fcb4..f45b8fe 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1934,6 +1934,7 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
#endif
#define READ_CAPACITY_RETRIES_ON_RESET 10
+#define READ_CAPACITY_RETRIES_ON_TRANSITION 120
static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
unsigned char *buffer)
@@ -1943,6 +1944,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
int sense_valid = 0;
int the_result;
int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
+ int transition_retries = READ_CAPACITY_RETRIES_ON_TRANSITION;
unsigned int alignment;
unsigned long long lba;
unsigned sector_size;
@@ -1981,6 +1983,15 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
* give it one more chance */
if (--reset_retries > 0)
continue;
+ if (sense_valid &&
+ sshdr.sense_key == NOT_READY &&
+ sshdr.asc == 0x04 && sshdr.ascq == 0x0A) {
+ /* ALUA state transition; retry after delay */
+ if (--transition_retries > 0) {
+ msleep(1000);
+ continue;
+ }
+ }
}
retries--;
@@ -2039,6 +2050,7 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
int sense_valid = 0;
int the_result;
int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
+ int transition_retries = READ_CAPACITY_RETRIES_ON_TRANSITION;
sector_t lba;
unsigned sector_size;
@@ -2063,6 +2075,15 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
* give it one more chance */
if (--reset_retries > 0)
continue;
+ if (sense_valid &&
+ sshdr.sense_key == NOT_READY &&
+ sshdr.asc == 0x04 && sshdr.ascq == 0x0A) {
+ /* ALUA state transition; retry after delay */
+ if (--transition_retries > 0) {
+ msleep(1000);
+ continue;
+ }
+ }
}
retries--;
Hello Hannes,
Although I agree that multipathd should handle arrays correctly that
fail READ CAPACITY commands while transitioning, seeing that a new
hard-coded timeout is added in the SCSI initiator code does not make me
enthusiast. The READ_CAPACITY_RETRIES_ON_TRANSITION timeout added
through this patch is independent of the IMPLICIT TRANSITION TIME in the
REPORT TARGET PORT GROUPS response. Has the following already been
considered ?
- If the capacity is not known, let the scsi_dh_alua handler submit a
READ CAPACITY command asynchronously after certain target port group
state transitions. Also let the scsi_dh_alua handler submit a
notification to user space after the capacity changes from "unknown" to
"known".
- Let multipathd ignore paths for which READ CAPACITY failed until the
capacity becomes known.
Thanks,
Bart.
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