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.
  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
  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.
  26          If unsure, say N.
  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).
  36          If unsure, say N.
  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.
  49          If unsure, say Y.
  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.
  61          LZO is not the standard compression used in Squashfs and so most
  62          file systems will be readable without selecting this option.
  64          If unsure, say N.
  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.
  76          XZ is not the standard compression used in Squashfs and so most
  77          file systems will be readable without selecting this option.
  79          If unsure, say N.
  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.
  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).
  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.
  98          Setting this option will force Squashfs to use a 4K device block
  99          size by default.
 101          If unsure, say N.
 104        bool "Additional option for memory-constrained systems"
 105        depends on SQUASHFS
 106        help
 107          Saying Y here allows you to specify cache size.
 109          If unsure, say N.
 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.
 122          Note there must be at least one cached fragment.  Anything
 123          much more than three will probably not make much difference.
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