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 57 config SQUASHFS_DECOMP_SINGLE
58 depends on SQUASHFS 58 depends on SQUASHFS
59 def_bool n 59 def_bool n
60 60
61 config SQUASHFS_DECOMP_MULTI 61 config SQUASHFS_DECOMP_MULTI
62 depends on SQUASHFS 62 depends on SQUASHFS
63 def_bool n 63 def_bool n
64 64
65 config SQUASHFS_DECOMP_MULTI_PERCPU 65 config SQUASHFS_DECOMP_MULTI_PERCPU
66 depends on SQUASHFS 66 depends on SQUASHFS
67 def_bool n 67 def_bool n
68 68
69 config SQUASHFS_CHOICE_DECOMP_BY_MOUNT 69 config SQUASHFS_CHOICE_DECOMP_BY_MOUNT
70 bool "Select the parallel decompressio 70 bool "Select the parallel decompression mode during mount"
71 depends on SQUASHFS 71 depends on SQUASHFS
72 default n 72 default n
73 select SQUASHFS_DECOMP_SINGLE 73 select SQUASHFS_DECOMP_SINGLE
74 select SQUASHFS_DECOMP_MULTI 74 select SQUASHFS_DECOMP_MULTI
75 select SQUASHFS_DECOMP_MULTI_PERCPU 75 select SQUASHFS_DECOMP_MULTI_PERCPU
76 select SQUASHFS_MOUNT_DECOMP_THREADS 76 select SQUASHFS_MOUNT_DECOMP_THREADS
77 help 77 help
78 Compile all parallel decompression m 78 Compile all parallel decompression modes and specify the
79 decompression mode by setting "threa 79 decompression mode by setting "threads=" during mount.
80 default Decompressor parallelisation 80 default Decompressor parallelisation is SQUASHFS_DECOMP_SINGLE
81 81
82 choice 82 choice
83 prompt "Select decompression parallel 83 prompt "Select decompression parallel mode at compile time"
84 depends on SQUASHFS 84 depends on SQUASHFS
85 depends on !SQUASHFS_CHOICE_DECOMP_BY_ 85 depends on !SQUASHFS_CHOICE_DECOMP_BY_MOUNT
86 help 86 help
87 Squashfs now supports three parallel 87 Squashfs now supports three parallelisation options for
88 decompression. Each one exhibits va 88 decompression. Each one exhibits various trade-offs between
89 decompression performance and CPU an 89 decompression performance and CPU and memory usage.
90 90
91 If in doubt, select "Single threaded 91 If in doubt, select "Single threaded compression"
92 92
93 config SQUASHFS_COMPILE_DECOMP_SINGLE 93 config SQUASHFS_COMPILE_DECOMP_SINGLE
94 bool "Single threaded compression" 94 bool "Single threaded compression"
95 select SQUASHFS_DECOMP_SINGLE 95 select SQUASHFS_DECOMP_SINGLE
96 help 96 help
97 Traditionally Squashfs has used sing 97 Traditionally Squashfs has used single-threaded decompression.
98 Only one block (data or metadata) ca 98 Only one block (data or metadata) can be decompressed at any
99 one time. This limits CPU and memor 99 one time. This limits CPU and memory usage to a minimum.
100 100
101 config SQUASHFS_COMPILE_DECOMP_MULTI 101 config SQUASHFS_COMPILE_DECOMP_MULTI
102 bool "Use multiple decompressors for p 102 bool "Use multiple decompressors for parallel I/O"
103 select SQUASHFS_DECOMP_MULTI 103 select SQUASHFS_DECOMP_MULTI
104 help 104 help
105 By default Squashfs uses a single de 105 By default Squashfs uses a single decompressor but it gives
106 poor performance on parallel I/O wor 106 poor performance on parallel I/O workloads when using multiple CPU
107 machines due to waiting on decompres 107 machines due to waiting on decompressor availability.
108 108
109 If you have a parallel I/O workload 109 If you have a parallel I/O workload and your system has enough memory,
110 using this option may improve overal 110 using this option may improve overall I/O performance.
111 111
112 This decompressor implementation use 112 This decompressor implementation uses up to two parallel
113 decompressors per core. It dynamica 113 decompressors per core. It dynamically allocates decompressors
114 on a demand basis. 114 on a demand basis.
115 115
116 config SQUASHFS_COMPILE_DECOMP_MULTI_PERCPU 116 config SQUASHFS_COMPILE_DECOMP_MULTI_PERCPU
117 bool "Use percpu multiple decompressor 117 bool "Use percpu multiple decompressors for parallel I/O"
118 select SQUASHFS_DECOMP_MULTI_PERCPU 118 select SQUASHFS_DECOMP_MULTI_PERCPU
119 help 119 help
120 By default Squashfs uses a single de 120 By default Squashfs uses a single decompressor but it gives
121 poor performance on parallel I/O wor 121 poor performance on parallel I/O workloads when using multiple CPU
122 machines due to waiting on decompres 122 machines due to waiting on decompressor availability.
123 123
124 This decompressor implementation use 124 This decompressor implementation uses a maximum of one
125 decompressor per core. It uses perc 125 decompressor per core. It uses percpu variables to ensure
126 decompression is load-balanced acros 126 decompression is load-balanced across the cores.
127 endchoice 127 endchoice
128 128
129 config SQUASHFS_MOUNT_DECOMP_THREADS 129 config SQUASHFS_MOUNT_DECOMP_THREADS
130 bool "Add the mount parameter 'threads 130 bool "Add the mount parameter 'threads=' for squashfs"
131 depends on SQUASHFS 131 depends on SQUASHFS
132 depends on SQUASHFS_DECOMP_MULTI 132 depends on SQUASHFS_DECOMP_MULTI
133 default n 133 default n
134 help 134 help
135 Use threads= to set the decompressio 135 Use threads= to set the decompression parallel mode and the number of threads.
136 If SQUASHFS_CHOICE_DECOMP_BY_MOUNT=y 136 If SQUASHFS_CHOICE_DECOMP_BY_MOUNT=y
137 threads=<single|multi|percpu|1|2 137 threads=<single|multi|percpu|1|2|3|...>
138 else 138 else
139 threads=<2|3|...> 139 threads=<2|3|...>
140 The upper limit is num_online_cpus() 140 The upper limit is num_online_cpus() * 2.
141 141
142 config SQUASHFS_XATTR 142 config SQUASHFS_XATTR
143 bool "Squashfs XATTR support" 143 bool "Squashfs XATTR support"
144 depends on SQUASHFS 144 depends on SQUASHFS
145 help 145 help
146 Saying Y here includes support for e 146 Saying Y here includes support for extended attributes (xattrs).
147 Xattrs are name:value pairs associat 147 Xattrs are name:value pairs associated with inodes by
148 the kernel or by users (see the attr 148 the kernel or by users (see the attr(5) manual page).
149 149
150 If unsure, say N. 150 If unsure, say N.
151 151
152 config SQUASHFS_ZLIB 152 config SQUASHFS_ZLIB
153 bool "Include support for ZLIB compres 153 bool "Include support for ZLIB compressed file systems"
154 depends on SQUASHFS 154 depends on SQUASHFS
155 select ZLIB_INFLATE 155 select ZLIB_INFLATE
156 default y 156 default y
157 help 157 help
158 ZLIB compression is the standard com 158 ZLIB compression is the standard compression used by Squashfs
159 file systems. It offers a good trad 159 file systems. It offers a good trade-off between compression
160 achieved and the amount of CPU time 160 achieved and the amount of CPU time and memory necessary to
161 compress and decompress. 161 compress and decompress.
162 162
163 If unsure, say Y. 163 If unsure, say Y.
164 164
165 config SQUASHFS_LZ4 165 config SQUASHFS_LZ4
166 bool "Include support for LZ4 compress 166 bool "Include support for LZ4 compressed file systems"
167 depends on SQUASHFS 167 depends on SQUASHFS
168 select LZ4_DECOMPRESS 168 select LZ4_DECOMPRESS
169 help 169 help
170 Saying Y here includes support for r 170 Saying Y here includes support for reading Squashfs file systems
171 compressed with LZ4 compression. LZ 171 compressed with LZ4 compression. LZ4 compression is mainly
172 aimed at embedded systems with slowe 172 aimed at embedded systems with slower CPUs where the overheads
173 of zlib are too high. 173 of zlib are too high.
174 174
175 LZ4 is not the standard compression 175 LZ4 is not the standard compression used in Squashfs and so most
176 file systems will be readable withou 176 file systems will be readable without selecting this option.
177 177
178 If unsure, say N. 178 If unsure, say N.
179 179
180 config SQUASHFS_LZO 180 config SQUASHFS_LZO
181 bool "Include support for LZO compress 181 bool "Include support for LZO compressed file systems"
182 depends on SQUASHFS 182 depends on SQUASHFS
183 select LZO_DECOMPRESS 183 select LZO_DECOMPRESS
184 help 184 help
185 Saying Y here includes support for r 185 Saying Y here includes support for reading Squashfs file systems
186 compressed with LZO compression. LZ 186 compressed with LZO compression. LZO compression is mainly
187 aimed at embedded systems with slowe 187 aimed at embedded systems with slower CPUs where the overheads
188 of zlib are too high. 188 of zlib are too high.
189 189
190 LZO is not the standard compression 190 LZO is not the standard compression used in Squashfs and so most
191 file systems will be readable withou 191 file systems will be readable without selecting this option.
192 192
193 If unsure, say N. 193 If unsure, say N.
194 194
195 config SQUASHFS_XZ 195 config SQUASHFS_XZ
196 bool "Include support for XZ compresse 196 bool "Include support for XZ compressed file systems"
197 depends on SQUASHFS 197 depends on SQUASHFS
198 select XZ_DEC 198 select XZ_DEC
199 help 199 help
200 Saying Y here includes support for r 200 Saying Y here includes support for reading Squashfs file systems
201 compressed with XZ compression. XZ 201 compressed with XZ compression. XZ gives better compression than
202 the default zlib compression, at the 202 the default zlib compression, at the expense of greater CPU and
203 memory overhead. 203 memory overhead.
204 204
205 XZ is not the standard compression u 205 XZ is not the standard compression used in Squashfs and so most
206 file systems will be readable withou 206 file systems will be readable without selecting this option.
207 207
208 If unsure, say N. 208 If unsure, say N.
209 209
210 config SQUASHFS_ZSTD 210 config SQUASHFS_ZSTD
211 bool "Include support for ZSTD compres 211 bool "Include support for ZSTD compressed file systems"
212 depends on SQUASHFS 212 depends on SQUASHFS
213 select ZSTD_DECOMPRESS 213 select ZSTD_DECOMPRESS
214 help 214 help
215 Saying Y here includes support for r 215 Saying Y here includes support for reading Squashfs file systems
216 compressed with ZSTD compression. Z 216 compressed with ZSTD compression. ZSTD gives better compression than
217 the default ZLIB compression, while 217 the default ZLIB compression, while using less CPU.
218 218
219 ZSTD is not the standard compression 219 ZSTD is not the standard compression used in Squashfs and so most
220 file systems will be readable withou 220 file systems will be readable without selecting this option.
221 221
222 If unsure, say N. 222 If unsure, say N.
223 223
224 config SQUASHFS_4K_DEVBLK_SIZE 224 config SQUASHFS_4K_DEVBLK_SIZE
225 bool "Use 4K device block size?" 225 bool "Use 4K device block size?"
226 depends on SQUASHFS 226 depends on SQUASHFS
227 help 227 help
228 By default Squashfs sets the dev blo 228 By default Squashfs sets the dev block size (sb_min_blocksize)
229 to 1K or the smallest block size sup 229 to 1K or the smallest block size supported by the block device
230 (if larger). This, because blocks a 230 (if larger). This, because blocks are packed together and
231 unaligned in Squashfs, should reduce 231 unaligned in Squashfs, should reduce latency.
232 232
233 This, however, gives poor performanc 233 This, however, gives poor performance on MTD NAND devices where
234 the optimal I/O size is 4K (even tho 234 the optimal I/O size is 4K (even though the devices can support
235 smaller block sizes). 235 smaller block sizes).
236 236
237 Using a 4K device block size may als 237 Using a 4K device block size may also improve overall I/O
238 performance for some file access pat 238 performance for some file access patterns (e.g. sequential
239 accesses of files in filesystem orde 239 accesses of files in filesystem order) on all media.
240 240
241 Setting this option will force Squas 241 Setting this option will force Squashfs to use a 4K device block
242 size by default. 242 size by default.
243 243
244 If unsure, say N. 244 If unsure, say N.
245 245
246 config SQUASHFS_EMBEDDED 246 config SQUASHFS_EMBEDDED
247 bool "Additional option for memory-con 247 bool "Additional option for memory-constrained systems"
248 depends on SQUASHFS 248 depends on SQUASHFS
249 help 249 help
250 Saying Y here allows you to specify 250 Saying Y here allows you to specify cache size.
251 251
252 If unsure, say N. 252 If unsure, say N.
253 253
254 config SQUASHFS_FRAGMENT_CACHE_SIZE 254 config SQUASHFS_FRAGMENT_CACHE_SIZE
255 int "Number of fragments cached" if SQ 255 int "Number of fragments cached" if SQUASHFS_EMBEDDED
256 depends on SQUASHFS 256 depends on SQUASHFS
257 default "3" 257 default "3"
258 help 258 help
259 By default SquashFS caches the last 259 By default SquashFS caches the last 3 fragments read from
260 the filesystem. Increasing this amo 260 the filesystem. Increasing this amount may mean SquashFS
261 has to re-read fragments less often 261 has to re-read fragments less often from disk, at the expense
262 of extra system memory. Decreasing 262 of extra system memory. Decreasing this amount will mean
263 SquashFS uses less memory at the exp 263 SquashFS uses less memory at the expense of extra reads from disk.
264 264
265 Note there must be at least one cach 265 Note there must be at least one cached fragment. Anything
266 much more than three will probably n 266 much more than three will probably not make much difference.
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