fs/squashfs/Kconfig

   1 config 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
  28 config 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
  38 config 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
  51 config 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
  66 config 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
  81 config 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
 103 config 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
 111 config 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.