multipath: Increase dev_loss_tmo prior to fast_io_fail

There are several constraints when setting fast_io_fail and
dev_loss_tmo.
dev_loss_tmo will be capped automatically when fast_io_fail is
not set. And fast_io_fail can not be raised beyond dev_loss_tmo.

So to increase dev_loss_tmo and fast_io_fail we first need
to increase dev_loss_tmo to the given fast_io_fail
setting, then set fast_io_fail, and then set dev_loss_tmo
to the final setting.

Signed-off-by: Hannes Reinecke <hare@suse.de>

diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index f6f182e..6af5083 100644 (file)
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -317,6 +317,7 @@ sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
        struct udev_device *rport_dev = NULL;
        char value[11];
        char rport_id[32];
+       unsigned long long tmo;
 
        sprintf(rport_id, "rport-%d:%d-%d",
                pp->sg_id.host_no, pp->sg_id.channel, pp->sg_id.transport_id);
@@ -330,23 +331,51 @@ sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
        condlog(4, "target%d:%d:%d -> %s", pp->sg_id.host_no,
                pp->sg_id.channel, pp->sg_id.scsi_id, rport_id);
 
-       snprintf(value, 11, "%u", mpp->dev_loss);
-       if (mpp->dev_loss &&
-           sysfs_attr_set_value(rport_dev, "dev_loss_tmo", value, 11) <= 0) {
-               if ((mpp->fast_io_fail == MP_FAST_IO_FAIL_UNSET ||
-                    mpp->fast_io_fail == MP_FAST_IO_FAIL_OFF)
-                   && mpp->dev_loss > 600) {
-                       condlog(3, "%s: limiting dev_loss_tmo to 600, since "
-                               "fast_io_fail is not set", mpp->alias);
-                       snprintf(value, 11, "%u", 600);
-                       if (sysfs_attr_set_value(rport_dev, "dev_loss_tmo",
-                                                value, 11) <= 0)
-                               condlog(0, "%s failed to set dev_loss_tmo",
-                                       mpp->alias);
+       /*
+        * This is tricky.
+        * dev_loss_tmo will be limited to 600 if fast_io_fail
+        * is _not_ set.
+        * fast_io_fail will be limited by the current dev_loss_tmo
+        * setting.
+        * So to get everything right we first need to increase
+        * dev_loss_tmo to the fast_io_fail setting (if present),
+        * then set fast_io_fail, and _then_ set dev_loss_tmo
+        * to the correct value.
+        */
+       value[0] = '\0';
+       if (mpp->fast_io_fail != MP_FAST_IO_FAIL_UNSET &&
+           mpp->fast_io_fail != MP_FAST_IO_FAIL_OFF) {
+               /* Check if we need to temporarily increase dev_loss_tmo */
+               if (sysfs_attr_get_value(rport_dev, "dev_loss_tmo",
+                                        value, 16) <= 0) {
+                       condlog(0, "%s: failed to read dev_loss_tmo value, "
+                               "error %d", pp->dev, errno);
+                       goto out;
+               }
+               if (sscanf(value, "%llu\n", &tmo) != 1) {
+                       condlog(0, "%s: Cannot parse dev_loss_tmo "
+                               "attribute '%s'",pp->dev, value);
                        goto out;
                }
+               if (mpp->fast_io_fail >= tmo) {
+                       snprintf(value, 11, "%u", mpp->fast_io_fail);
+               } else {
+                       tmo = 0;
+               }
+       } else if (mpp->dev_loss > 600) {
+               condlog(3, "%s: limiting dev_loss_tmo to 600, since "
+                       "fast_io_fail is not set", pp->dev);
+               snprintf(value, 11, "%u", 600);
+       } else {
+               snprintf(value, 11, "%u", mpp->dev_loss);
        }
-       if (mpp->fast_io_fail != MP_FAST_IO_FAIL_UNSET){
+       if (strlen(value) &&
+           sysfs_attr_set_value(rport_dev, "dev_loss_tmo", value, 11) <= 0) {
+               condlog(0, "%s failed to set dev_loss_tmo",
+                       mpp->alias);
+               goto out;
+       }
+       if (mpp->fast_io_fail != MP_FAST_IO_FAIL_UNSET) {
                if (mpp->fast_io_fail == MP_FAST_IO_FAIL_OFF)
                        sprintf(value, "off");
                else if (mpp->fast_io_fail == MP_FAST_IO_FAIL_ZERO)
@@ -359,6 +388,13 @@ sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
                                mpp->alias);
                }
        }
+       if (tmo > 0) {
+               snprintf(value, 11, "%u", mpp->dev_loss);
+               if (sysfs_attr_set_value(rport_dev, "dev_loss_tmo",
+                                        value, 11) <= 0)
+                       condlog(0, "%s failed to set dev_loss_tmo",
+                               mpp->alias);
+       }
 out:
        udev_device_unref(rport_dev);
 }
@@ -394,7 +430,7 @@ sysfs_set_session_tmo(struct multipath *mpp, struct path *pp)
                } else {
                        snprintf(value, 11, "%u", mpp->fast_io_fail);
                        if (sysfs_attr_set_value(session_dev, "recovery_tmo",
-                                                value, 11)) {
+                                                value, 11) <= 0) {
                                condlog(3, "%s: Failed to set recovery_tmo, "
                                        " error %d", pp->dev, errno);
                        }

diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index d33747f..22b73b1 100644 (file)
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -38,6 +38,62 @@
 #include "debug.h"
 #include "devmapper.h"
 
+/*
+ * When we modify an attribute value we cannot rely on libudev for now,
+ * as libudev lacks the capability to update an attribute value.
+ * So for modified attributes we need to implement our own function.
+ */
+ssize_t sysfs_attr_get_value(struct udev_device *dev, const char *attr_name,
+                            char * value, size_t value_len)
+{
+       char devpath[PATH_SIZE];
+       struct stat statbuf;
+       int fd;
+       ssize_t size = -1;
+
+       if (!dev || !attr_name || !value)
+               return 0;
+
+       snprintf(devpath, PATH_SIZE, "%s/%s", udev_device_get_syspath(dev),
+                attr_name);
+       condlog(4, "open '%s'", devpath);
+       if (stat(devpath, &statbuf) != 0) {
+               condlog(4, "stat '%s' failed: %s", devpath, strerror(errno));
+               return 0;
+       }
+
+       /* skip directories */
+       if (S_ISDIR(statbuf.st_mode)) {
+               condlog(4, "%s is a directory", devpath);
+               return 0;
+       }
+
+       /* skip non-writeable files */
+       if ((statbuf.st_mode & S_IRUSR) == 0) {
+               condlog(4, "%s is not readable", devpath);
+               return 0;
+       }
+
+       /* read attribute value */
+       fd = open(devpath, O_RDONLY);
+       if (fd < 0) {
+               condlog(4, "attribute '%s' can not be opened: %s",
+                       devpath, strerror(errno));
+               return 0;
+       }
+       size = read(fd, value, value_len);
+       if (size < 0) {
+               condlog(4, "read from %s failed: %s", devpath, strerror(errno));
+               size = 0;
+       } else if (size == value_len) {
+               condlog(4, "overflow while reading from %s", devpath);
+               size = 0;
+       }
+
+       close(fd);
+       return size;
+}
+
 ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
                             char * value, size_t value_len)
 {
@@ -58,12 +114,16 @@ ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
        }
 
        /* skip directories */
-       if (S_ISDIR(statbuf.st_mode))
+       if (S_ISDIR(statbuf.st_mode)) {
+               condlog(4, "%s is a directory", devpath);
                return 0;
+       }
 
        /* skip non-writeable files */
-       if ((statbuf.st_mode & S_IWUSR) == 0)
+       if ((statbuf.st_mode & S_IWUSR) == 0) {
+               condlog(4, "%s is not writeable", devpath);
                return 0;
+       }
 
        /* write attribute value */
        fd = open(devpath, O_WRONLY);

diff --git a/libmultipath/sysfs.h b/libmultipath/sysfs.h
index 13d7545..34f3e00 100644 (file)
--- a/libmultipath/sysfs.h
+++ b/libmultipath/sysfs.h
@@ -7,6 +7,8 @@
 
 ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
                             char * value, size_t value_len);
+ssize_t sysfs_attr_get_value(struct udev_device *dev, const char *attr_name,
+                            char * value, size_t value_len);
 int sysfs_get_size (struct path *pp, unsigned long long * size);
 int sysfs_check_holders(char * check_devt, char * new_devt);
 #endif