scsi: target: tcmu: Make pgr_support and alua_support attributes writable

Currently in tcmu reservation commands are handled by core's pr
implementation (default) or completely rejected (emulate_pr set to 0). We
additionally want to be able to do full reservation handling in
userspace. Therefore we need a way to set TRANSPORT_FLAG_PASSTHROUGH_PGR.

The inverted flag is displayed by attribute pgr_support.  Since we moved
the flag from transport/backend to se_device in the previous commit, we now
can make it changeable per device by allowing to write the attribute.  The
new field transport_flags_changeable in transport/backend is used to reject
writing if not allowed for a backend.

Regarding ALUA we also want to be able to passthrough commands to userspace
in tcmu. Therefore we need TRANSPORT_FLAG_PASSTHROUGH_ALUA to be
changeable, because by setting it we can switch off all ALUA checks in
core. So we also set TRANSPORT_FLAG_PASSTHROUGH_ALUA in tcmu's
transport_flags_changeable.

Of course, ALUA and reservation handling in userspace will work only, if
session/nexus information is sent to userspace along with every
command. This will be object of a patch series announced by Mike Christie.

Link: https://lore.kernel.org/r/20200427150823.15350-5-bstroesser@ts.fujitsu.com
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 279989e..f043522 100644 (file)
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1105,6 +1105,32 @@ static ssize_t alua_support_show(struct config_item *item, char *page)
                        flags & TRANSPORT_FLAG_PASSTHROUGH_ALUA ? 0 : 1);
 }
 
+static ssize_t alua_support_store(struct config_item *item,
+               const char *page, size_t count)
+{
+       struct se_dev_attrib *da = to_attrib(item);
+       struct se_device *dev = da->da_dev;
+       bool flag;
+       int ret;
+
+       if (!(dev->transport->transport_flags_changeable &
+             TRANSPORT_FLAG_PASSTHROUGH_ALUA)) {
+               pr_err("dev[%p]: Unable to change SE Device alua_support:"
+                       " alua_support has fixed value\n", dev);
+               return -EINVAL;
+       }
+
+       ret = strtobool(page, &flag);
+       if (ret < 0)
+               return ret;
+
+       if (flag)
+               dev->transport_flags &= ~TRANSPORT_FLAG_PASSTHROUGH_ALUA;
+       else
+               dev->transport_flags |= TRANSPORT_FLAG_PASSTHROUGH_ALUA;
+       return count;
+}
+
 static ssize_t pgr_support_show(struct config_item *item, char *page)
 {
        struct se_dev_attrib *da = to_attrib(item);
@@ -1114,6 +1140,32 @@ static ssize_t pgr_support_show(struct config_item *item, char *page)
                        flags & TRANSPORT_FLAG_PASSTHROUGH_PGR ? 0 : 1);
 }
 
+static ssize_t pgr_support_store(struct config_item *item,
+               const char *page, size_t count)
+{
+       struct se_dev_attrib *da = to_attrib(item);
+       struct se_device *dev = da->da_dev;
+       bool flag;
+       int ret;
+
+       if (!(dev->transport->transport_flags_changeable &
+             TRANSPORT_FLAG_PASSTHROUGH_PGR)) {
+               pr_err("dev[%p]: Unable to change SE Device pgr_support:"
+                       " pgr_support has fixed value\n", dev);
+               return -EINVAL;
+       }
+
+       ret = strtobool(page, &flag);
+       if (ret < 0)
+               return ret;
+
+       if (flag)
+               dev->transport_flags &= ~TRANSPORT_FLAG_PASSTHROUGH_PGR;
+       else
+               dev->transport_flags |= TRANSPORT_FLAG_PASSTHROUGH_PGR;
+       return count;
+}
+
 CONFIGFS_ATTR(, emulate_model_alias);
 CONFIGFS_ATTR(, emulate_dpo);
 CONFIGFS_ATTR(, emulate_fua_write);
@@ -1146,8 +1198,8 @@ CONFIGFS_ATTR(, unmap_granularity);
 CONFIGFS_ATTR(, unmap_granularity_alignment);
 CONFIGFS_ATTR(, unmap_zeroes_data);
 CONFIGFS_ATTR(, max_write_same_len);
-CONFIGFS_ATTR_RO(, alua_support);
-CONFIGFS_ATTR_RO(, pgr_support);
+CONFIGFS_ATTR(, alua_support);
+CONFIGFS_ATTR(, pgr_support);
 
 /*
  * dev_attrib attributes for devices using the target core SBC/SPC

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index cb388b2..72ffd35 100644 (file)
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -2617,6 +2617,8 @@ static struct target_backend_ops tcmu_ops = {
        .name                   = "user",
        .owner                  = THIS_MODULE,
        .transport_flags_default = TRANSPORT_FLAG_PASSTHROUGH,
+       .transport_flags_changeable = TRANSPORT_FLAG_PASSTHROUGH_PGR |
+                                     TRANSPORT_FLAG_PASSTHROUGH_ALUA,
        .attach_hba             = tcmu_attach_hba,
        .detach_hba             = tcmu_detach_hba,
        .alloc_device           = tcmu_alloc_device,

diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index 9591635..f51452e 100644 (file)
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -24,6 +24,7 @@ struct target_backend_ops {
        struct module *owner;
 
        u8 transport_flags_default;
+       u8 transport_flags_changeable;
 
        int (*attach_hba)(struct se_hba *, u32);
        void (*detach_hba)(struct se_hba *);