d9c740d225
* 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>
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| .. | ||
| BUGS | ||
| common.h | ||
| dir.c | ||
| exofs.h | ||
| file.c | ||
| inode.c | ||
| ios.c | ||
| Kbuild | ||
| Kconfig | ||
| namei.c | ||
| pnfs.h | ||
| super.c | ||
| symlink.c | ||