exofs: Define on-disk per-inode optional layout attribute
* Layouts describe the way a file is spread on multiple devices.
The layout information is stored in the objects attribute introduced
in this patch.
* There can be multiple generating function for the layout.
Currently defined:
- No attribute present - use below moving-window on global
device table, all devices.
(This is the only one currently used in exofs)
- an obj_id generated moving window - the obj_id is a randomizing
factor in the otherwise global map layout.
- An explicit layout stored, including a data_map and a device
index list.
- More might be defined in future ...
* There are two attributes defined of the same structure:
A-data-files-layout - This layout is used by data-files. If present
at a directory, all files of that directory will
be created with this layout.
A-meta-data-layout - This layout is used by a directory and other
meta-data information. Also inherited at creation
of subdirectories.
* At creation time inodes are created with the layout specified above.
A usermode utility may change the creation layout on a give directory
or file. Which in the case of directories, will also apply to newly
created files/subdirectories, children of that directory.
In the simple unaltered case of a newly created exofs, no layout
attributes are present, and all layouts adhere to the layout specified
at the device-table.
* In case of a future file system loaded in an old exofs-driver.
At iget(), the generating_function is inspected and if not supported
will return an IO error to the application and the inode will not
be loaded. So not to damage any data.
Note: After this patch we do not yet support any type of layout
only the RAID0 patch that enables striping at the super-block
level will add support for RAID0 layouts above. This way we
are past and future compatible and fully bisectable.
* Access to the device table is done by an accessor since
it will change according to above information.
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/exofs/common.h b/fs/exofs/common.h
index b1b178e..f0d5203 100644
--- a/fs/exofs/common.h
+++ b/fs/exofs/common.h
@@ -55,6 +55,8 @@
/* exofs Application specific page/attribute */
# define EXOFS_APAGE_FS_DATA (OSD_APAGE_APP_DEFINED_FIRST + 3)
# define EXOFS_ATTR_INODE_DATA 1
+# define EXOFS_ATTR_INODE_FILE_LAYOUT 2
+# define EXOFS_ATTR_INODE_DIR_LAYOUT 3
/*
* The maximum number of files we can have is limited by the size of the
@@ -206,4 +208,41 @@
(((name_len) + offsetof(struct exofs_dir_entry, name) + \
EXOFS_DIR_ROUND) & ~EXOFS_DIR_ROUND)
+/*
+ * The on-disk (optional) layout structure.
+ * sits in an EXOFS_ATTR_INODE_FILE_LAYOUT or EXOFS_ATTR_INODE_DIR_LAYOUT
+ * attribute, attached to any inode, usually to a directory.
+ */
+
+enum exofs_inode_layout_gen_functions {
+ LAYOUT_MOVING_WINDOW = 0,
+ LAYOUT_IMPLICT = 1,
+};
+
+struct exofs_on_disk_inode_layout {
+ __le16 gen_func; /* One of enum exofs_inode_layout_gen_functions */
+ __le16 pad;
+ union {
+ /* gen_func == LAYOUT_MOVING_WINDOW (default) */
+ struct exofs_layout_sliding_window {
+ __le32 num_devices; /* first n devices in global-table*/
+ } sliding_window __packed;
+
+ /* gen_func == LAYOUT_IMPLICT */
+ struct exofs_layout_implict_list {
+ struct exofs_dt_data_map data_map;
+ /* Variable array of size data_map.cb_num_comps. These
+ * are device indexes of the devices in the global table
+ */
+ __le32 dev_indexes[];
+ } implict __packed;
+ };
+} __packed;
+
+static inline size_t exofs_on_disk_inode_layout_size(unsigned max_devs)
+{
+ return sizeof(struct exofs_on_disk_inode_layout) +
+ max_devs * sizeof(__le32);
+}
+
#endif /*ifndef __EXOFS_COM_H__*/
