mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 20:53:53 +08:00
9ed9648431
If /dev/osd* devices are shuffled because more devices where added, and/or login order has changed. It is hard to mount the FS you want. Add an option to mount by osdname. osdname is any osd-device's osdname as specified to the mkfs.exofs command when formatting the osd-devices. The new mount format is: OPT="osdname=$UUID0,pid=$PID,_netdev" mount -t exofs -o $OPT $DEV_OSD0 $MOUNTDIR if "osdname=" is specified in options above $DEV_OSD0 is ignored and can be empty. Also while at it: Removed some old unused Opt_* enums. Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
186 lines
8.5 KiB
Plaintext
186 lines
8.5 KiB
Plaintext
===============================================================================
|
|
WHAT IS EXOFS?
|
|
===============================================================================
|
|
|
|
exofs is a file system that uses an OSD and exports the API of a normal Linux
|
|
file system. Users access exofs like any other local file system, and exofs
|
|
will in turn issue commands to the local OSD initiator.
|
|
|
|
OSD is a new T10 command set that views storage devices not as a large/flat
|
|
array of sectors but as a container of objects, each having a length, quota,
|
|
time attributes and more. Each object is addressed by a 64bit ID, and is
|
|
contained in a 64bit ID partition. Each object has associated attributes
|
|
attached to it, which are integral part of the object and provide metadata about
|
|
the object. The standard defines some common obligatory attributes, but user
|
|
attributes can be added as needed.
|
|
|
|
===============================================================================
|
|
ENVIRONMENT
|
|
===============================================================================
|
|
|
|
To use this file system, you need to have an object store to run it on. You
|
|
may download a target from:
|
|
http://open-osd.org
|
|
|
|
See Documentation/scsi/osd.txt for how to setup a working osd environment.
|
|
|
|
===============================================================================
|
|
USAGE
|
|
===============================================================================
|
|
|
|
1. Download and compile exofs and open-osd initiator:
|
|
You need an external Kernel source tree or kernel headers from your
|
|
distribution. (anything based on 2.6.26 or later).
|
|
|
|
a. download open-osd including exofs source using:
|
|
[parent-directory]$ 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.
|