Lines Matching +full:i +full:- +full:cache +full:- +full:block +full:- +full:size
4 Squashfs is a compressed read-only filesystem for Linux.
7 minimise data overhead. Block sizes greater than 4K are supported up to a
8 maximum of 1Mbytes (default block size 128K).
10 Squashfs is intended for general read-only filesystem use, for archival
11 use (i.e. in cases where a .tar.gz file may be used), and in constrained
12 block device/memory systems (e.g. embedded systems) where low overhead is
15 Mailing list: squashfs-devel@lists.sourceforge.net
19 ----------------------
25 Max filesystem size: 2^64 256 MiB
26 Max file size: ~ 2 TiB 16 MiB
30 Max block size: 1 MiB 4 KiB
34 Tail-end packing (fragments): yes no
39 32-bit uids/gids: yes no
47 file type, i.e. regular file, directory, symbolic link, and block/char device
51 -----------------
53 As squashfs is a read-only filesystem, the mksquashfs program must be used to
58 The squashfs-tools development tree is now located on kernel.org
59 git://git.kernel.org/pub/scm/fs/squashfs/squashfs-tools.git
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103 dictionary size). If non-default compression options have been used, then
107 ----------
110 compressed block is prefixed by a two byte length, the top bit is set if the
111 block is uncompressed. A block will be uncompressed if the -noI option is set,
112 or if the compressed block was larger than the uncompressed block.
114 Inodes are packed into the metadata blocks, and are not aligned to block
116 by a 48-bit number which encodes the location of the compressed metadata block
117 containing the inode, and the byte offset into that block where the inode is
118 placed (<block, offset>).
130 ---------------
135 decompressed block (<block, offset>).
140 compressed metadata block, and therefore, can share the start block.
142 header containing the shared start block value, and a sequence of directory
143 entries, each of which share the shared start block. A new directory header
144 is written once/if the inode start block changes. The directory
150 in each metadata block. Directories are sorted in alphabetical order,
153 location of the metadata block the filename is in has been found.
154 The general idea of the index is to ensure only one metadata block needs to be
160 -------------
163 compressed fragment block (tail-end packed block). The compressed size
164 of each datablock is stored in a block list contained within the
168 larger), the code implements an index cache that caches the mapping from
169 block index to datablock location on disk.
171 The index cache allows Squashfs to handle large files (up to 1.75 TiB) while
172 retaining a simple and space-efficient block list on disk. The cache
175 The index cache is designed to be memory efficient, and by default uses
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182 location on disk and compressed size using a fragment lookup table. This
189 ------------------------
192 converted to 32-bit uids/gids using an id look up table. This table is
198 ----------------
201 can optionally (disabled with the -no-exports Mksquashfs option) contain
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223 also allows values to be de-duplicated, the value being stored once, and
227 To reduce overhead in inodes, rather than storing the on-disk
228 location of the xattr list inside each inode, a 32-bit xattr id
233 -------------------------------
236 -------------
240 4.2 Squashfs internal cache
241 ---------------------------
246 The cache is not used for file datablocks, these are decompressed and cached in
247 the page-cache in the normal way. The cache is used to temporarily cache
249 (i.e. inode or directory) or fragment access. Because metadata and fragments
252 which have been packed with it, these because of locality-of-reference may be
256 In the future this internal cache may be replaced with an implementation which
257 uses the kernel page cache. Because the page cache operates on page sized