1config SQUASHFS 2 tristate "SquashFS 4.0 - Squashed file system support" 3 depends on BLOCK 4 help 5 Saying Y here includes support for SquashFS 4.0 (a Compressed 6 Read-Only File System). Squashfs is a highly compressed read-only 7 filesystem for Linux. It uses zlib, lzo or xz compression to 8 compress both files, inodes and directories. Inodes in the system 9 are very small and all blocks are packed to minimise data overhead. 10 Block sizes greater than 4K are supported up to a maximum of 1 Mbytes 11 (default block size 128K). SquashFS 4.0 supports 64 bit filesystems 12 and files (larger than 4GB), full uid/gid information, hard links and 13 timestamps. 14 15 Squashfs is intended for general read-only filesystem use, for 16 archival use (i.e. in cases where a .tar.gz file may be used), and in 17 embedded systems where low overhead is needed. Further information 18 and tools are available from http://squashfs.sourceforge.net. 19 20 If you want to compile this as a module ( = code which can be 21 inserted in and removed from the running kernel whenever you want), 22 say M here. The module will be called squashfs. Note that the root 23 file system (the one containing the directory /) cannot be compiled 24 as a module. 25 26 If unsure, say N. 27 28config SQUASHFS_XATTR 29 bool "Squashfs XATTR support" 30 depends on SQUASHFS 31 help 32 Saying Y here includes support for extended attributes (xattrs). 33 Xattrs are name:value pairs associated with inodes by 34 the kernel or by users (see the attr(5) manual page). 35 36 If unsure, say N. 37 38config SQUASHFS_ZLIB 39 bool "Include support for ZLIB compressed file systems" 40 depends on SQUASHFS 41 select ZLIB_INFLATE 42 default y 43 help 44 ZLIB compression is the standard compression used by Squashfs 45 file systems. It offers a good trade-off between compression 46 achieved and the amount of CPU time and memory necessary to 47 compress and decompress. 48 49 If unsure, say Y. 50 51config SQUASHFS_LZO 52 bool "Include support for LZO compressed file systems" 53 depends on SQUASHFS 54 select LZO_DECOMPRESS 55 help 56 Saying Y here includes support for reading Squashfs file systems 57 compressed with LZO compression. LZO compression is mainly 58 aimed at embedded systems with slower CPUs where the overheads 59 of zlib are too high. 60 61 LZO is not the standard compression used in Squashfs and so most 62 file systems will be readable without selecting this option. 63 64 If unsure, say N. 65 66config SQUASHFS_XZ 67 bool "Include support for XZ compressed file systems" 68 depends on SQUASHFS 69 select XZ_DEC 70 help 71 Saying Y here includes support for reading Squashfs file systems 72 compressed with XZ compression. XZ gives better compression than 73 the default zlib compression, at the expense of greater CPU and 74 memory overhead. 75 76 XZ is not the standard compression used in Squashfs and so most 77 file systems will be readable without selecting this option. 78 79 If unsure, say N. 80 81config SQUASHFS_4K_DEVBLK_SIZE 82 bool "Use 4K device block size?" 83 depends on SQUASHFS 84 help 85 By default Squashfs sets the dev block size (sb_min_blocksize) 86 to 1K or the smallest block size supported by the block device 87 (if larger). This, because blocks are packed together and 88 unaligned in Squashfs, should reduce latency. 89 90 This, however, gives poor performance on MTD NAND devices where 91 the optimal I/O size is 4K (even though the devices can support 92 smaller block sizes). 93 94 Using a 4K device block size may also improve overall I/O 95 performance for some file access patterns (e.g. sequential 96 accesses of files in filesystem order) on all media. 97 98 Setting this option will force Squashfs to use a 4K device block 99 size by default. 100 101 If unsure, say N. 102 103config SQUASHFS_EMBEDDED 104 bool "Additional option for memory-constrained systems" 105 depends on SQUASHFS 106 help 107 Saying Y here allows you to specify cache size. 108 109 If unsure, say N. 110 111config SQUASHFS_FRAGMENT_CACHE_SIZE 112 int "Number of fragments cached" if SQUASHFS_EMBEDDED 113 depends on SQUASHFS 114 default "3" 115 help 116 By default SquashFS caches the last 3 fragments read from 117 the filesystem. Increasing this amount may mean SquashFS 118 has to re-read fragments less often from disk, at the expense 119 of extra system memory. Decreasing this amount will mean 120 SquashFS uses less memory at the expense of extra reads from disk. 121 122 Note there must be at least one cached fragment. Anything 123 much more than three will probably not make much difference. 124