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