Re: sg_persist triggers block kernel event ???

[Christophe Varoqui <christophe.varoqui@xxxxxxxxxxx>]

It seems sg_persist is doing an "open rw => close" for --in commands, causing a kernel change-event.

I can not verify at the moment if the following patch would work ... comments ?

--- sg_persist.c.orig 2014-05-04 01:10:01.987981956 +0200

+++ sg_persist.c 2014-05-04 01:15:34.880008000 +0200

@@ -1029,6 +1029,8 @@

     struct sg_simple_inquiry_resp inq_resp;

     const char * cp;

     struct opts_t opts;

+    int omode = 0;

+    const char *omode_desc = NULL;

 

     memset(&opts, 0, sizeof(opts));

     opts.prin = 1;

@@ -1292,10 +1294,18 @@

         sg_cmds_close_device(sg_fd);

     }

 

-    if ((sg_fd = sg_cmds_open_device(device_name, 0 /* rw */,

+    if (opts.prin) {

+        omode = 1;

+        omode_desc = "ro";

+    } else {

+        omode = 0;

+        omode_desc = "rw";

+    }

+

+    if ((sg_fd = sg_cmds_open_device(device_name, omode,

                                      opts.verbose)) < 0) {

-        pr2serr("sg_persist: error opening file (rw): %s: %s\n", device_name,

-                safe_strerror(-sg_fd));

+        pr2serr("sg_persist: error opening file (%s): %s: %s\n", omode_desc,

+                device_name, safe_strerror(-sg_fd));

         return SG_LIB_FILE_ERROR;

     }

 

Regards,

Christophe Varoqui

www.opensvc.com

On Sat, May 3, 2014 at 10:12 PM, Christophe Varoqui <christophe.varoqui@xxxxxxxxxxx> wrote:

Hi list,

I observe this on a debian 7.5 server with a udevadm monitor running in the background :

# sg_persist -n -k /dev/sdbh

  PR generation=0x0, there are NO registered reservation keys

KERNEL[448809.342461] change   /devices/pci0000:20/0000:20:02.2/0000:24:00.0/host0/rport-0:0-3/target0:0:1/0:0:1:12/block/sdbh (block)

ACTION="">

DEVNAME=/dev/sdbh

DEVPATH=/devices/pci0000:20/0000:20:02.2/0000:24:00.0/host0/rport-0:0-3/target0:0:1/0:0:1:12/block/sdbh

DEVTYPE=disk

MAJOR=67

MINOR=176

SEQNUM=261605

SUBSYSTEM=block

Every sg_persist command, with any options, trigger events.

On this server with more than 200 scsi devices, each receiving one read-key and one read-reservation every 10 minutes, this triggers quite a eavy load caused by 2 udev triggers :

1/ multipath -v0 $devpath

2/ udisks-lvm-pv-export $pv_uuid

Question is, is it normal for a "--in" sg_persist command to trigger a change event on the scsi device ? If not, what we can do about it ?

Best regards,

Christophe Varoqui

www.opensvc.com

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