From d9c740d2253e75db8cef8f87a3125c450f3ebd82 Mon Sep 17 00:00:00 2001 From: Boaz Harrosh Date: Thu, 28 Jan 2010 11:58:08 +0200 Subject: 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 --- fs/exofs/common.h | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'fs/exofs/common.h') diff --git a/fs/exofs/common.h b/fs/exofs/common.h index b1b178e61718..f0d520312d8b 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 @@ enum { (((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__*/ -- cgit v1.2.3