| config SQUASHFS |
| tristate "SquashFS 4.0 - Squashed file system support" |
| depends on BLOCK |
| help |
| Saying Y here includes support for SquashFS 4.0 (a Compressed |
| Read-Only File System). Squashfs is a highly compressed read-only |
| filesystem for Linux. It uses zlib, lzo or xz compression to |
| compress both files, inodes and directories. Inodes in the system |
| are very small and all blocks are packed to minimise data overhead. |
| Block sizes greater than 4K are supported up to a maximum of 1 Mbytes |
| (default block size 128K). SquashFS 4.0 supports 64 bit filesystems |
| and files (larger than 4GB), full uid/gid information, hard links and |
| timestamps. |
| |
| Squashfs is intended for general read-only filesystem use, for |
| archival use (i.e. in cases where a .tar.gz file may be used), and in |
| embedded systems where low overhead is needed. Further information |
| and tools are available from http://squashfs.sourceforge.net. |
| |
| If you want to compile this as a module ( = code which can be |
| inserted in and removed from the running kernel whenever you want), |
| say M here and read <file:Documentation/modules.txt>. The module |
| will be called squashfs. Note that the root file system (the one |
| containing the directory /) cannot be compiled as a module. |
| |
| If unsure, say N. |
| |
| config SQUASHFS_XATTR |
| bool "Squashfs XATTR support" |
| depends on SQUASHFS |
| help |
| Saying Y here includes support for extended attributes (xattrs). |
| Xattrs are name:value pairs associated with inodes by |
| the kernel or by users (see the attr(5) manual page). |
| |
| If unsure, say N. |
| |
| config SQUASHFS_ZLIB |
| bool "Include support for ZLIB compressed file systems" |
| depends on SQUASHFS |
| select ZLIB_INFLATE |
| default y |
| help |
| ZLIB compression is the standard compression used by Squashfs |
| file systems. It offers a good trade-off between compression |
| achieved and the amount of CPU time and memory necessary to |
| compress and decompress. |
| |
| If unsure, say Y. |
| |
| config SQUASHFS_LZO |
| bool "Include support for LZO compressed file systems" |
| depends on SQUASHFS |
| select LZO_DECOMPRESS |
| help |
| Saying Y here includes support for reading Squashfs file systems |
| compressed with LZO compression. LZO compression is mainly |
| aimed at embedded systems with slower CPUs where the overheads |
| of zlib are too high. |
| |
| LZO is not the standard compression used in Squashfs and so most |
| file systems will be readable without selecting this option. |
| |
| If unsure, say N. |
| |
| config SQUASHFS_XZ |
| bool "Include support for XZ compressed file systems" |
| depends on SQUASHFS |
| select XZ_DEC |
| help |
| Saying Y here includes support for reading Squashfs file systems |
| compressed with XZ compression. XZ gives better compression than |
| the default zlib compression, at the expense of greater CPU and |
| memory overhead. |
| |
| XZ is not the standard compression used in Squashfs and so most |
| file systems will be readable without selecting this option. |
| |
| If unsure, say N. |
| |
| config SQUASHFS_4K_DEVBLK_SIZE |
| bool "Use 4K device block size?" |
| depends on SQUASHFS |
| help |
| By default Squashfs sets the dev block size (sb_min_blocksize) |
| to 1K or the smallest block size supported by the block device |
| (if larger). This, because blocks are packed together and |
| unaligned in Squashfs, should reduce latency. |
| |
| This, however, gives poor performance on MTD NAND devices where |
| the optimal I/O size is 4K (even though the devices can support |
| smaller block sizes). |
| |
| Using a 4K device block size may also improve overall I/O |
| performance for some file access patterns (e.g. sequential |
| accesses of files in filesystem order) on all media. |
| |
| Setting this option will force Squashfs to use a 4K device block |
| size by default. |
| |
| If unsure, say N. |
| |
| config SQUASHFS_EMBEDDED |
| bool "Additional option for memory-constrained systems" |
| depends on SQUASHFS |
| help |
| Saying Y here allows you to specify cache size. |
| |
| If unsure, say N. |
| |
| config SQUASHFS_FRAGMENT_CACHE_SIZE |
| int "Number of fragments cached" if SQUASHFS_EMBEDDED |
| depends on SQUASHFS |
| default "3" |
| help |
| By default SquashFS caches the last 3 fragments read from |
| the filesystem. Increasing this amount may mean SquashFS |
| has to re-read fragments less often from disk, at the expense |
| of extra system memory. Decreasing this amount will mean |
| SquashFS uses less memory at the expense of extra reads from disk. |
| |
| Note there must be at least one cached fragment. Anything |
| much more than three will probably not make much difference. |