1 # SPDX-License-Identifier: GPL-2.0-only <<
2 config SQUASHFS 1 config SQUASHFS
3 tristate "SquashFS 4.0 - Squashed file 2 tristate "SquashFS 4.0 - Squashed file system support"
4 depends on BLOCK 3 depends on BLOCK
5 help 4 help
6 Saying Y here includes support for S 5 Saying Y here includes support for SquashFS 4.0 (a Compressed
7 Read-Only File System). Squashfs is 6 Read-Only File System). Squashfs is a highly compressed read-only
8 filesystem for Linux. It uses zlib, 7 filesystem for Linux. It uses zlib, lzo or xz compression to
9 compress both files, inodes and dire 8 compress both files, inodes and directories. Inodes in the system
10 are very small and all blocks are pa 9 are very small and all blocks are packed to minimise data overhead.
11 Block sizes greater than 4K are supp 10 Block sizes greater than 4K are supported up to a maximum of 1 Mbytes
12 (default block size 128K). SquashFS 11 (default block size 128K). SquashFS 4.0 supports 64 bit filesystems
13 and files (larger than 4GB), full ui 12 and files (larger than 4GB), full uid/gid information, hard links and
14 timestamps. 13 timestamps.
15 14
16 Squashfs is intended for general rea 15 Squashfs is intended for general read-only filesystem use, for
17 archival use (i.e. in cases where a 16 archival use (i.e. in cases where a .tar.gz file may be used), and in
18 embedded systems where low overhead 17 embedded systems where low overhead is needed. Further information
19 and tools are available from http:// 18 and tools are available from http://squashfs.sourceforge.net.
20 19
21 If you want to compile this as a mod 20 If you want to compile this as a module ( = code which can be
22 inserted in and removed from the run 21 inserted in and removed from the running kernel whenever you want),
23 say M here. The module will be call 22 say M here. The module will be called squashfs. Note that the root
24 file system (the one containing the 23 file system (the one containing the directory /) cannot be compiled
25 as a module. 24 as a module.
26 25
27 If unsure, say N. 26 If unsure, say N.
28 27
29 choice 28 choice
30 prompt "File decompression options" 29 prompt "File decompression options"
31 depends on SQUASHFS 30 depends on SQUASHFS
32 help 31 help
33 Squashfs now supports two options fo 32 Squashfs now supports two options for decompressing file
34 data. Traditionally Squashfs has de 33 data. Traditionally Squashfs has decompressed into an
35 intermediate buffer and then memcopi 34 intermediate buffer and then memcopied it into the page cache.
36 Squashfs now supports the ability to 35 Squashfs now supports the ability to decompress directly into
37 the page cache. 36 the page cache.
38 37
39 If unsure, select "Decompress file d 38 If unsure, select "Decompress file data into an intermediate buffer"
40 39
41 config SQUASHFS_FILE_CACHE 40 config SQUASHFS_FILE_CACHE
42 bool "Decompress file data into an int 41 bool "Decompress file data into an intermediate buffer"
43 help 42 help
44 Decompress file data into an interme 43 Decompress file data into an intermediate buffer and then
45 memcopy it into the page cache. 44 memcopy it into the page cache.
46 45
47 config SQUASHFS_FILE_DIRECT 46 config SQUASHFS_FILE_DIRECT
48 bool "Decompress files directly into t 47 bool "Decompress files directly into the page cache"
49 help 48 help
50 Directly decompress file data into t 49 Directly decompress file data into the page cache.
51 Doing so can significantly improve p 50 Doing so can significantly improve performance because
52 it eliminates a memcpy and it also r 51 it eliminates a memcpy and it also removes the lock contention
53 on the single buffer. 52 on the single buffer.
54 53
55 endchoice 54 endchoice
56 55
57 config SQUASHFS_DECOMP_SINGLE <<
58 depends on SQUASHFS <<
59 def_bool n <<
60 <<
61 config SQUASHFS_DECOMP_MULTI <<
62 depends on SQUASHFS <<
63 def_bool n <<
64 <<
65 config SQUASHFS_DECOMP_MULTI_PERCPU <<
66 depends on SQUASHFS <<
67 def_bool n <<
68 <<
69 config SQUASHFS_CHOICE_DECOMP_BY_MOUNT <<
70 bool "Select the parallel decompressio <<
71 depends on SQUASHFS <<
72 default n <<
73 select SQUASHFS_DECOMP_SINGLE <<
74 select SQUASHFS_DECOMP_MULTI <<
75 select SQUASHFS_DECOMP_MULTI_PERCPU <<
76 select SQUASHFS_MOUNT_DECOMP_THREADS <<
77 help <<
78 Compile all parallel decompression m <<
79 decompression mode by setting "threa <<
80 default Decompressor parallelisation <<
81 <<
82 choice 56 choice
83 prompt "Select decompression parallel !! 57 prompt "Decompressor parallelisation options"
84 depends on SQUASHFS 58 depends on SQUASHFS
85 depends on !SQUASHFS_CHOICE_DECOMP_BY_ <<
86 help 59 help
87 Squashfs now supports three parallel 60 Squashfs now supports three parallelisation options for
88 decompression. Each one exhibits va 61 decompression. Each one exhibits various trade-offs between
89 decompression performance and CPU an 62 decompression performance and CPU and memory usage.
90 63
91 If in doubt, select "Single threaded 64 If in doubt, select "Single threaded compression"
92 65
93 config SQUASHFS_COMPILE_DECOMP_SINGLE !! 66 config SQUASHFS_DECOMP_SINGLE
94 bool "Single threaded compression" 67 bool "Single threaded compression"
95 select SQUASHFS_DECOMP_SINGLE <<
96 help 68 help
97 Traditionally Squashfs has used sing 69 Traditionally Squashfs has used single-threaded decompression.
98 Only one block (data or metadata) ca 70 Only one block (data or metadata) can be decompressed at any
99 one time. This limits CPU and memor 71 one time. This limits CPU and memory usage to a minimum.
100 72
101 config SQUASHFS_COMPILE_DECOMP_MULTI !! 73 config SQUASHFS_DECOMP_MULTI
102 bool "Use multiple decompressors for p 74 bool "Use multiple decompressors for parallel I/O"
103 select SQUASHFS_DECOMP_MULTI <<
104 help 75 help
105 By default Squashfs uses a single de 76 By default Squashfs uses a single decompressor but it gives
106 poor performance on parallel I/O wor 77 poor performance on parallel I/O workloads when using multiple CPU
107 machines due to waiting on decompres 78 machines due to waiting on decompressor availability.
108 79
109 If you have a parallel I/O workload 80 If you have a parallel I/O workload and your system has enough memory,
110 using this option may improve overal 81 using this option may improve overall I/O performance.
111 82
112 This decompressor implementation use 83 This decompressor implementation uses up to two parallel
113 decompressors per core. It dynamica 84 decompressors per core. It dynamically allocates decompressors
114 on a demand basis. 85 on a demand basis.
115 86
116 config SQUASHFS_COMPILE_DECOMP_MULTI_PERCPU !! 87 config SQUASHFS_DECOMP_MULTI_PERCPU
117 bool "Use percpu multiple decompressor 88 bool "Use percpu multiple decompressors for parallel I/O"
118 select SQUASHFS_DECOMP_MULTI_PERCPU <<
119 help 89 help
120 By default Squashfs uses a single de 90 By default Squashfs uses a single decompressor but it gives
121 poor performance on parallel I/O wor 91 poor performance on parallel I/O workloads when using multiple CPU
122 machines due to waiting on decompres 92 machines due to waiting on decompressor availability.
123 93
124 This decompressor implementation use 94 This decompressor implementation uses a maximum of one
125 decompressor per core. It uses perc 95 decompressor per core. It uses percpu variables to ensure
126 decompression is load-balanced acros 96 decompression is load-balanced across the cores.
127 endchoice <<
128 97
129 config SQUASHFS_MOUNT_DECOMP_THREADS !! 98 endchoice
130 bool "Add the mount parameter 'threads <<
131 depends on SQUASHFS <<
132 depends on SQUASHFS_DECOMP_MULTI <<
133 default n <<
134 help <<
135 Use threads= to set the decompressio <<
136 If SQUASHFS_CHOICE_DECOMP_BY_MOUNT=y <<
137 threads=<single|multi|percpu|1|2 <<
138 else <<
139 threads=<2|3|...> <<
140 The upper limit is num_online_cpus() <<
141 99
142 config SQUASHFS_XATTR 100 config SQUASHFS_XATTR
143 bool "Squashfs XATTR support" 101 bool "Squashfs XATTR support"
144 depends on SQUASHFS 102 depends on SQUASHFS
145 help 103 help
146 Saying Y here includes support for e 104 Saying Y here includes support for extended attributes (xattrs).
147 Xattrs are name:value pairs associat 105 Xattrs are name:value pairs associated with inodes by
148 the kernel or by users (see the attr 106 the kernel or by users (see the attr(5) manual page).
149 107
150 If unsure, say N. 108 If unsure, say N.
151 109
152 config SQUASHFS_ZLIB 110 config SQUASHFS_ZLIB
153 bool "Include support for ZLIB compres 111 bool "Include support for ZLIB compressed file systems"
154 depends on SQUASHFS 112 depends on SQUASHFS
155 select ZLIB_INFLATE 113 select ZLIB_INFLATE
156 default y 114 default y
157 help 115 help
158 ZLIB compression is the standard com 116 ZLIB compression is the standard compression used by Squashfs
159 file systems. It offers a good trad 117 file systems. It offers a good trade-off between compression
160 achieved and the amount of CPU time 118 achieved and the amount of CPU time and memory necessary to
161 compress and decompress. 119 compress and decompress.
162 120
163 If unsure, say Y. 121 If unsure, say Y.
164 122
165 config SQUASHFS_LZ4 123 config SQUASHFS_LZ4
166 bool "Include support for LZ4 compress 124 bool "Include support for LZ4 compressed file systems"
167 depends on SQUASHFS 125 depends on SQUASHFS
168 select LZ4_DECOMPRESS 126 select LZ4_DECOMPRESS
169 help 127 help
170 Saying Y here includes support for r 128 Saying Y here includes support for reading Squashfs file systems
171 compressed with LZ4 compression. LZ 129 compressed with LZ4 compression. LZ4 compression is mainly
172 aimed at embedded systems with slowe 130 aimed at embedded systems with slower CPUs where the overheads
173 of zlib are too high. 131 of zlib are too high.
174 132
175 LZ4 is not the standard compression 133 LZ4 is not the standard compression used in Squashfs and so most
176 file systems will be readable withou 134 file systems will be readable without selecting this option.
177 135
178 If unsure, say N. 136 If unsure, say N.
179 137
180 config SQUASHFS_LZO 138 config SQUASHFS_LZO
181 bool "Include support for LZO compress 139 bool "Include support for LZO compressed file systems"
182 depends on SQUASHFS 140 depends on SQUASHFS
183 select LZO_DECOMPRESS 141 select LZO_DECOMPRESS
184 help 142 help
185 Saying Y here includes support for r 143 Saying Y here includes support for reading Squashfs file systems
186 compressed with LZO compression. LZ 144 compressed with LZO compression. LZO compression is mainly
187 aimed at embedded systems with slowe 145 aimed at embedded systems with slower CPUs where the overheads
188 of zlib are too high. 146 of zlib are too high.
189 147
190 LZO is not the standard compression 148 LZO is not the standard compression used in Squashfs and so most
191 file systems will be readable withou 149 file systems will be readable without selecting this option.
192 150
193 If unsure, say N. 151 If unsure, say N.
194 152
195 config SQUASHFS_XZ 153 config SQUASHFS_XZ
196 bool "Include support for XZ compresse 154 bool "Include support for XZ compressed file systems"
197 depends on SQUASHFS 155 depends on SQUASHFS
198 select XZ_DEC 156 select XZ_DEC
199 help 157 help
200 Saying Y here includes support for r 158 Saying Y here includes support for reading Squashfs file systems
201 compressed with XZ compression. XZ 159 compressed with XZ compression. XZ gives better compression than
202 the default zlib compression, at the 160 the default zlib compression, at the expense of greater CPU and
203 memory overhead. 161 memory overhead.
204 162
205 XZ is not the standard compression u 163 XZ is not the standard compression used in Squashfs and so most
206 file systems will be readable withou <<
207 <<
208 If unsure, say N. <<
209 <<
210 config SQUASHFS_ZSTD <<
211 bool "Include support for ZSTD compres <<
212 depends on SQUASHFS <<
213 select ZSTD_DECOMPRESS <<
214 help <<
215 Saying Y here includes support for r <<
216 compressed with ZSTD compression. Z <<
217 the default ZLIB compression, while <<
218 <<
219 ZSTD is not the standard compression <<
220 file systems will be readable withou 164 file systems will be readable without selecting this option.
221 165
222 If unsure, say N. 166 If unsure, say N.
223 167
224 config SQUASHFS_4K_DEVBLK_SIZE 168 config SQUASHFS_4K_DEVBLK_SIZE
225 bool "Use 4K device block size?" 169 bool "Use 4K device block size?"
226 depends on SQUASHFS 170 depends on SQUASHFS
227 help 171 help
228 By default Squashfs sets the dev blo 172 By default Squashfs sets the dev block size (sb_min_blocksize)
229 to 1K or the smallest block size sup 173 to 1K or the smallest block size supported by the block device
230 (if larger). This, because blocks a 174 (if larger). This, because blocks are packed together and
231 unaligned in Squashfs, should reduce 175 unaligned in Squashfs, should reduce latency.
232 176
233 This, however, gives poor performanc 177 This, however, gives poor performance on MTD NAND devices where
234 the optimal I/O size is 4K (even tho 178 the optimal I/O size is 4K (even though the devices can support
235 smaller block sizes). 179 smaller block sizes).
236 180
237 Using a 4K device block size may als 181 Using a 4K device block size may also improve overall I/O
238 performance for some file access pat 182 performance for some file access patterns (e.g. sequential
239 accesses of files in filesystem orde 183 accesses of files in filesystem order) on all media.
240 184
241 Setting this option will force Squas 185 Setting this option will force Squashfs to use a 4K device block
242 size by default. 186 size by default.
243 187
244 If unsure, say N. 188 If unsure, say N.
245 189
246 config SQUASHFS_EMBEDDED 190 config SQUASHFS_EMBEDDED
247 bool "Additional option for memory-con 191 bool "Additional option for memory-constrained systems"
248 depends on SQUASHFS 192 depends on SQUASHFS
249 help 193 help
250 Saying Y here allows you to specify 194 Saying Y here allows you to specify cache size.
251 195
252 If unsure, say N. 196 If unsure, say N.
253 197
254 config SQUASHFS_FRAGMENT_CACHE_SIZE 198 config SQUASHFS_FRAGMENT_CACHE_SIZE
255 int "Number of fragments cached" if SQ 199 int "Number of fragments cached" if SQUASHFS_EMBEDDED
256 depends on SQUASHFS 200 depends on SQUASHFS
257 default "3" 201 default "3"
258 help 202 help
259 By default SquashFS caches the last 203 By default SquashFS caches the last 3 fragments read from
260 the filesystem. Increasing this amo 204 the filesystem. Increasing this amount may mean SquashFS
261 has to re-read fragments less often 205 has to re-read fragments less often from disk, at the expense
262 of extra system memory. Decreasing 206 of extra system memory. Decreasing this amount will mean
263 SquashFS uses less memory at the exp 207 SquashFS uses less memory at the expense of extra reads from disk.
264 208
265 Note there must be at least one cach 209 Note there must be at least one cached fragment. Anything
266 much more than three will probably n 210 much more than three will probably not make much difference.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.