Re: [dm-devel] [PATCH 3/3] multipathd: Add 'sysfs' prioritizer

2016-12-07 Thread Xose Vazquez Perez 
On 11/09/2016 07:49 AM, Hannes Reinecke wrote:

> On 11/08/2016 07:52 PM, Xose Vazquez Perez wrote:
>> On 07/15/2016 08:48 AM, Hannes Reinecke wrote:
>>
>>> Recent kernels have an 'access_state' attribute which allows
>>> us to read the asymmetric access state directly from sysfs.
>>
>> Hi Hannes,
>>
>> with this patch it's impossible to select/autodetect ALUA.
>> sysfs always takes precedence over alua.
>>
>> "detect_prio no" was added to overrides section, to make
>> it work again.
>>
>> SLES 12-SP2
>>
>> Thank you.
>>
> But this was precisely the idea.
> (After all, it says 'auto-detect', right?)
> 
> For ALUA-capable arrays we have a reliable priority detection with the ALUA 
> device-handler.
> So it's far preferable to use the sysfs-provided information (as they are 
> populated by the ALUA device-handler); the ALUA prioritizer in 
> multipath-tools will be used as a fallback in case the device
> handler isn't loaded or the sysfs files are not present.
> Using the sysfs handler has the neat side effect that you don't need to do 
> I/O for detecting the priority, thereby eliminating one possible cause for 
> multipath being stuck during failover.

Thanks for the explanation.


As collateral effect, because the sysfs-handler output is too
brief, the asymmetric access state(aas) was lost:


Dec 07 19:26:51 | sda: prio = sysfs (detected setting)
Dec 07 19:26:51 | sda: sysfs prio = 50

Dec 07 19:26:29 | sdc: prio = alua (detected setting)
Dec 07 19:26:29 | reported target port group is 1   <- lost
Dec 07 19:26:29 | aas = 80 [active/optimized] [preferred]   <- lost
Dec 07 19:26:29 | sdc: alua prio = 50

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Re: [dm-devel] [PATCH 3/3] multipathd: Add 'sysfs' prioritizer

2016-11-08 Thread Hannes Reinecke 

On 11/08/2016 07:52 PM, Xose Vazquez Perez wrote:

On 07/15/2016 08:48 AM, Hannes Reinecke wrote:


Recent kernels have an 'access_state' attribute which allows
us to read the asymmetric access state directly from sysfs.


Hi Hannes,

with this patch it's impossible to select/autodetect ALUA.
sysfs always takes precedence over alua.

"detect_prio no" was added to overrides section, to make
it work again.

SLES 12-SP2

Thank you.


But this was precisely the idea.
(After all, it says 'auto-detect', right?)

For ALUA-capable arrays we have a reliable priority detection with the 
ALUA device-handler.
So it's far preferable to use the sysfs-provided information (as they 
are populated by the ALUA device-handler); the ALUA prioritizer in 
multipath-tools will be used as a fallback in case the device handler 
isn't loaded or the sysfs files are not present.
Using the sysfs handler has the neat side effect that you don't need to 
do I/O for detecting the priority, thereby eliminating one possible 
cause for multipath being stuck during failover.


Cheers,

Hannes
--
Dr. Hannes ReineckeTeamlead Storage & Networking
h...@suse.de   +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)

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Re: [dm-devel] [PATCH 3/3] multipathd: Add 'sysfs' prioritizer

2016-11-08 Thread Xose Vazquez Perez 
On 07/15/2016 08:48 AM, Hannes Reinecke wrote:

> Recent kernels have an 'access_state' attribute which allows
> us to read the asymmetric access state directly from sysfs.

Hi Hannes,

with this patch it's impossible to select/autodetect ALUA.
sysfs always takes precedence over alua.

"detect_prio no" was added to overrides section, to make
it work again.

SLES 12-SP2

Thank you.

> ---
>  libmultipath/discovery.c   | 33 +
>  libmultipath/discovery.h   |  2 ++
>  libmultipath/prio.h|  1 +
>  libmultipath/prioritizers/Makefile |  3 +-
>  libmultipath/prioritizers/sysfs.c  | 61 
> ++
>  libmultipath/propsel.c |  6 +++-
>  multipath/multipath.conf.5 | 19 ++--
>  7 files changed, 120 insertions(+), 5 deletions(-)
>  create mode 100644 libmultipath/prioritizers/sysfs.c
> 

[ ...]

> diff --git a/libmultipath/propsel.c b/libmultipath/propsel.c
> index beb0798..0caf269 100644
> --- a/libmultipath/propsel.c
> +++ b/libmultipath/propsel.c
> @@ -375,6 +375,8 @@ detect_prio(struct config *conf, struct path * pp)
>   struct prio *p = >prio;
>   int tpgs = 0;
>   unsigned int timeout = conf->checker_timeout;
> + char buff[512];
> + char *default_prio = PRIO_ALUA;
>  
>   if ((tpgs = get_target_port_group_support(pp->fd, timeout)) <= 0)
>   return;
> @@ -384,7 +386,9 @@ detect_prio(struct config *conf, struct path * pp)
>   return;
>   if (get_asymmetric_access_state(pp->fd, ret, timeout) < 0)
>   return;
> - prio_get(conf->multipath_dir, p, PRIO_ALUA, DEFAULT_PRIO_ARGS);
> + if (sysfs_get_asymmetric_access_state(pp, buff, 512) >= 0)
> + default_prio = PRIO_SYSFS;
> + prio_get(conf->multipath_dir, p, default_prio, DEFAULT_PRIO_ARGS);
>  }

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[dm-devel] [PATCH 3/3] multipathd: Add 'sysfs' prioritizer

2016-07-15 Thread Hannes Reinecke 
Recent kernels have an 'access_state' attribute which allows
us to read the asymmetric access state directly from sysfs.

Signed-off-by: Hannes Reinecke 
---
 libmultipath/discovery.c   | 33 +
 libmultipath/discovery.h   |  2 ++
 libmultipath/prio.h|  1 +
 libmultipath/prioritizers/Makefile |  3 +-
 libmultipath/prioritizers/sysfs.c  | 61 ++
 libmultipath/propsel.c |  6 +++-
 multipath/multipath.conf.5 | 19 ++--
 7 files changed, 120 insertions(+), 5 deletions(-)
 create mode 100644 libmultipath/prioritizers/sysfs.c

diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index e9e0313..07c60cf 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -209,6 +209,8 @@ declare_sysfs_get_str(devtype);
 declare_sysfs_get_str(vendor);
 declare_sysfs_get_str(model);
 declare_sysfs_get_str(rev);
+declare_sysfs_get_str(access_state);
+declare_sysfs_get_str(preferred_path);
 
 ssize_t
 sysfs_get_vpd (struct udev_device * udev, int pg,
@@ -484,6 +486,37 @@ int sysfs_get_iscsi_ip_address(struct path *pp, char 
*ip_address)
return 1;
 }
 
+int
+sysfs_get_asymmetric_access_state(struct path *pp, char *buff, int buflen)
+{
+   struct udev_device *parent = pp->udev;
+   char value[16], *eptr;
+   unsigned int preferred;
+
+   while (parent) {
+   const char *subsys = udev_device_get_subsystem(parent);
+   if (subsys && !strncmp(subsys, "scsi", 4))
+   break;
+   parent = udev_device_get_parent(parent);
+   }
+
+   if (!parent)
+   return -1;
+
+   if (sysfs_get_access_state(parent, buff, buflen) <= 0)
+   return -1;
+
+   if (sysfs_get_preferred_path(parent, value, 16) <= 0)
+   return 0;
+
+   preferred = strtoul(value, , 0);
+   if (value == eptr || preferred == ULONG_MAX) {
+   /* Parse error, ignore */
+   return 0;
+   }
+   return  preferred;
+}
+
 static void
 sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
 {
diff --git a/libmultipath/discovery.h b/libmultipath/discovery.h
index 321d930..0f5b1e6 100644
--- a/libmultipath/discovery.h
+++ b/libmultipath/discovery.h
@@ -47,6 +47,8 @@ int sysfs_get_host_pci_name(struct path *pp, char *pci_name);
 int sysfs_get_iscsi_ip_address(struct path *pp, char *ip_address);
 ssize_t sysfs_get_vpd (struct udev_device * udev, int pg, unsigned char * buff,
   size_t len);
+int sysfs_get_asymmetric_access_state(struct path *pp,
+ char *buff, int buflen);
 
 /*
  * discovery bitmask
diff --git a/libmultipath/prio.h b/libmultipath/prio.h
index 7195986..032028e 100644
--- a/libmultipath/prio.h
+++ b/libmultipath/prio.h
@@ -30,6 +30,7 @@ struct path;
 #define PRIO_RANDOM"random"
 #define PRIO_RDAC  "rdac"
 #define PRIO_WEIGHTED_PATH "weightedpath"
+#define PRIO_SYSFS "sysfs"
 
 /*
  * Value used to mark the fact prio was not defined
diff --git a/libmultipath/prioritizers/Makefile 
b/libmultipath/prioritizers/Makefile
index 903a139..bb76700 100644
--- a/libmultipath/prioritizers/Makefile
+++ b/libmultipath/prioritizers/Makefile
@@ -15,7 +15,8 @@ LIBS = \
libprioontap.so \
libpriorandom.so \
libpriordac.so \
-   libprioweightedpath.so
+   libprioweightedpath.so \
+   libpriosysfs.so
 
 CFLAGS += -I..
 
diff --git a/libmultipath/prioritizers/sysfs.c 
b/libmultipath/prioritizers/sysfs.c
new file mode 100644
index 000..ff567df
--- /dev/null
+++ b/libmultipath/prioritizers/sysfs.c
@@ -0,0 +1,61 @@
+/*
+ * sysfs.c
+ *
+ * Copyright(c) 2016 Hannes Reinecke, SUSE Linux GmbH
+ */
+
+#include 
+
+#include "structs.h"
+#include "discovery.h"
+#include "prio.h"
+
+static const struct {
+   unsigned char value;
+   char *name;
+} sysfs_access_state_map[] = {
+   { 50, "active/optimized" },
+   { 10, "active/non-optimized" },
+   {  5, "lba-dependent" },
+   {  1, "standby" },
+};
+
+int get_exclusive_pref_arg(char *args)
+{
+   char *ptr;
+
+   if (args == NULL)
+   return 0;
+   ptr = strstr(args, "exclusive_pref_bit");
+   if (!ptr)
+   return 0;
+   if (ptr[18] != '\0' && ptr[18] != ' ' && ptr[18] != '\t')
+   return 0;
+   if (ptr != args && ptr[-1] != ' ' && ptr[-1] != '\t')
+   return 0;
+   return 1;
+}
+
+int getprio (struct path * pp, char * args, unsigned int timeout)
+{
+   int prio = 0, rc, i;
+   char buff[512];
+   int exclusive_pref;
+
+   exclusive_pref = get_exclusive_pref_arg(args);
+   rc = sysfs_get_asymmetric_access_state(pp, buff, 512);
+   if (rc < 0)
+   return PRIO_UNDEF;
+   prio = 0;
+   for (i = 0; i < 4; i++) {
+   if (!strncmp(buff,