diff options
Diffstat (limited to 'Documentation/filesystems/configfs.rst')
| -rw-r--r-- | Documentation/filesystems/configfs.rst | 52 |
1 files changed, 2 insertions, 50 deletions
diff --git a/Documentation/filesystems/configfs.rst b/Documentation/filesystems/configfs.rst index f8941954c667..ac22138de6a4 100644 --- a/Documentation/filesystems/configfs.rst +++ b/Documentation/filesystems/configfs.rst @@ -226,7 +226,7 @@ filename. configfs_attribute->ca_mode specifies the file permissions. If an attribute is readable and provides a ->show method, that method will be called whenever userspace asks for a read(2) on the attribute. If an attribute is writable and provides a ->store method, that method will be -be called whenever userspace asks for a write(2) on the attribute. +called whenever userspace asks for a write(2) on the attribute. struct configfs_bin_attribute ============================= @@ -253,7 +253,7 @@ to be used. If binary attribute is readable and the config_item provides a ct_item_ops->read_bin_attribute() method, that method will be called whenever userspace asks for a read(2) on the attribute. The converse -will happen for write(2). The reads/writes are bufferred so only a +will happen for write(2). The reads/writes are buffered so only a single read/write will occur; the attributes' need not concern itself with it. @@ -289,7 +289,6 @@ config_item_type:: const char *name); struct config_group *(*make_group)(struct config_group *group, const char *name); - int (*commit_item)(struct config_item *item); void (*disconnect_notify)(struct config_group *group, struct config_item *item); void (*drop_item)(struct config_group *group, @@ -486,50 +485,3 @@ up. Here, the heartbeat code calls configfs_depend_item(). If it succeeds, then heartbeat knows the region is safe to give to ocfs2. If it fails, it was being torn down anyway, and heartbeat can gracefully pass up an error. - -Committable Items -================= - -Note: - Committable items are currently unimplemented. - -Some config_items cannot have a valid initial state. That is, no -default values can be specified for the item's attributes such that the -item can do its work. Userspace must configure one or more attributes, -after which the subsystem can start whatever entity this item -represents. - -Consider the FakeNBD device from above. Without a target address *and* -a target device, the subsystem has no idea what block device to import. -The simple example assumes that the subsystem merely waits until all the -appropriate attributes are configured, and then connects. This will, -indeed, work, but now every attribute store must check if the attributes -are initialized. Every attribute store must fire off the connection if -that condition is met. - -Far better would be an explicit action notifying the subsystem that the -config_item is ready to go. More importantly, an explicit action allows -the subsystem to provide feedback as to whether the attributes are -initialized in a way that makes sense. configfs provides this as -committable items. - -configfs still uses only normal filesystem operations. An item is -committed via rename(2). The item is moved from a directory where it -can be modified to a directory where it cannot. - -Any group that provides the ct_group_ops->commit_item() method has -committable items. When this group appears in configfs, mkdir(2) will -not work directly in the group. Instead, the group will have two -subdirectories: "live" and "pending". The "live" directory does not -support mkdir(2) or rmdir(2) either. It only allows rename(2). The -"pending" directory does allow mkdir(2) and rmdir(2). An item is -created in the "pending" directory. Its attributes can be modified at -will. Userspace commits the item by renaming it into the "live" -directory. At this point, the subsystem receives the ->commit_item() -callback. If all required attributes are filled to satisfaction, the -method returns zero and the item is moved to the "live" directory. - -As rmdir(2) does not work in the "live" directory, an item must be -shutdown, or "uncommitted". Again, this is done via rename(2), this -time from the "live" directory back to the "pending" one. The subsystem -is notified by the ct_group_ops->uncommit_object() method. |