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diff --git a/Documentation/filesystems/exofs.txt b/Documentation/filesystems/exofs.txt deleted file mode 100644 index 23583a136975..000000000000 --- a/Documentation/filesystems/exofs.txt +++ /dev/null @@ -1,185 +0,0 @@ -=============================================================================== -WHAT IS EXOFS? -=============================================================================== - -exofs is a file system that uses an OSD and exports the API of a normal Linux -file system. Users access exofs like any other local file system, and exofs -will in turn issue commands to the local OSD initiator. - -OSD is a new T10 command set that views storage devices not as a large/flat -array of sectors but as a container of objects, each having a length, quota, -time attributes and more. Each object is addressed by a 64bit ID, and is -contained in a 64bit ID partition. Each object has associated attributes -attached to it, which are integral part of the object and provide metadata about -the object. The standard defines some common obligatory attributes, but user -attributes can be added as needed. - -=============================================================================== -ENVIRONMENT -=============================================================================== - -To use this file system, you need to have an object store to run it on. You -may download a target from: -http://open-osd.org - -See Documentation/scsi/osd.txt for how to setup a working osd environment. - -=============================================================================== -USAGE -=============================================================================== - -1. Download and compile exofs and open-osd initiator: - You need an external Kernel source tree or kernel headers from your - distribution. (anything based on 2.6.26 or later). - - a. download open-osd including exofs source using: - [parent-directory]$ git clone git://git.open-osd.org/open-osd.git - - b. Build the library module like this: - [parent-directory]$ make -C KSRC=$(KER_DIR) open-osd - - This will build both the open-osd initiator as well as the exofs kernel - module. Use whatever parameters you compiled your Kernel with and - $(KER_DIR) above pointing to the Kernel you compile against. See the file - open-osd/top-level-Makefile for an example. - -2. Get the OSD initiator and target set up properly, and login to the target. - See Documentation/scsi/osd.txt for farther instructions. Also see ./do-osd - for example script that does all these steps. - -3. Insmod the exofs.ko module: - [exofs]$ insmod exofs.ko - -4. Make sure the directory where you want to mount exists. If not, create it. - (For example, mkdir /mnt/exofs) - -5. At first run you will need to invoke the mkfs.exofs application - - As an example, this will create the file system on: - /dev/osd0 partition ID 65536 - - mkfs.exofs --pid=65536 --format /dev/osd0 - - The --format is optional. If not specified, no OSD_FORMAT will be - performed and a clean file system will be created in the specified pid, - in the available space of the target. (Use --format=size_in_meg to limit - the total LUN space available) - - If pid already exists, it will be deleted and a new one will be created in - its place. Be careful. - - An exofs lives inside a single OSD partition. You can create multiple exofs - filesystems on the same device using multiple pids. - - (run mkfs.exofs without any parameters for usage help message) - -6. Mount the file system. - - For example, to mount /dev/osd0, partition ID 0x10000 on /mnt/exofs: - - mount -t exofs -o pid=65536 /dev/osd0 /mnt/exofs/ - -7. For reference (See do-exofs example script): - do-exofs start - an example of how to perform the above steps. - do-exofs stop - an example of how to unmount the file system. - do-exofs format - an example of how to format and mkfs a new exofs. - -8. Extra compilation flags (uncomment in fs/exofs/Kbuild): - CONFIG_EXOFS_DEBUG - for debug messages and extra checks. - -=============================================================================== -exofs mount options -=============================================================================== -Similar to any mount command: - mount -t exofs -o exofs_options /dev/osdX mount_exofs_directory - -Where: - -t exofs: specifies the exofs file system - - /dev/osdX: X is a decimal number. /dev/osdX was created after a successful - login into an OSD target. - - mount_exofs_directory: The directory to mount the file system on - - exofs specific options: Options are separated by commas (,) - pid=<integer> - The partition number to mount/create as - container of the filesystem. - This option is mandatory. integer can be - Hex by pre-pending an 0x to the number. - osdname=<id> - Mount by a device's osdname. - osdname is usually a 36 character uuid of the - form "d2683732-c906-4ee1-9dbd-c10c27bb40df". - It is one of the device's uuid specified in the - mkfs.exofs format command. - If this option is specified then the /dev/osdX - above can be empty and is ignored. - to=<integer> - Timeout in ticks for a single command. - default is (60 * HZ) [for debugging only] - -=============================================================================== -DESIGN -=============================================================================== - -* The file system control block (AKA on-disk superblock) resides in an object - with a special ID (defined in common.h). - Information included in the file system control block is used to fill the - in-memory superblock structure at mount time. This object is created before - the file system is used by mkexofs.c. It contains information such as: - - The file system's magic number - - The next inode number to be allocated - -* Each file resides in its own object and contains the data (and it will be - possible to extend the file over multiple objects, though this has not been - implemented yet). - -* A directory is treated as a file, and essentially contains a list of <file - name, inode #> pairs for files that are found in that directory. The object - IDs correspond to the files' inode numbers and will be allocated according to - a bitmap (stored in a separate object). Now they are allocated using a - counter. - -* Each file's control block (AKA on-disk inode) is stored in its object's - attributes. This applies to both regular files and other types (directories, - device files, symlinks, etc.). - -* Credentials are generated per object (inode and superblock) when they are - created in memory (read from disk or created). The credential works for all - operations and is used as long as the object remains in memory. - -* Async OSD operations are used whenever possible, but the target may execute - them out of order. The operations that concern us are create, delete, - readpage, writepage, update_inode, and truncate. The following pairs of - operations should execute in the order written, and we need to prevent them - from executing in reverse order: - - The following are handled with the OBJ_CREATED and OBJ_2BCREATED - flags. OBJ_CREATED is set when we know the object exists on the OSD - - in create's callback function, and when we successfully do a - read_inode. - OBJ_2BCREATED is set in the beginning of the create function, so we - know that we should wait. - - create/delete: delete should wait until the object is created - on the OSD. - - create/readpage: readpage should be able to return a page - full of zeroes in this case. If there was a write already - en-route (i.e. create, writepage, readpage) then the page - would be locked, and so it would really be the same as - create/writepage. - - create/writepage: if writepage is called for a sync write, it - should wait until the object is created on the OSD. - Otherwise, it should just return. - - create/truncate: truncate should wait until the object is - created on the OSD. - - create/update_inode: update_inode should wait until the - object is created on the OSD. - - Handled by VFS locks: - - readpage/delete: shouldn't happen because of page lock. - - writepage/delete: shouldn't happen because of page lock. - - readpage/writepage: shouldn't happen because of page lock. - -=============================================================================== -LICENSE/COPYRIGHT -=============================================================================== -The exofs file system is based on ext2 v0.5b (distributed with the Linux kernel -version 2.6.10). All files include the original copyrights, and the license -is GPL version 2 (only version 2, as is true for the Linux kernel). The -Linux kernel can be downloaded from www.kernel.org. |