^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ===============================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) CacheFiles: CACHE ON ALREADY MOUNTED FILESYSTEM
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) ===============================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) .. Contents:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) (*) Overview.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) (*) Requirements.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) (*) Configuration.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) (*) Starting the cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) (*) Things to avoid.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) (*) Cache culling.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) (*) Cache structure.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) (*) Security model and SELinux.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) (*) A note on security.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) (*) Statistical information.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) (*) Debugging.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Overview
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) CacheFiles is a caching backend that's meant to use as a cache a directory on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) an already mounted filesystem of a local type (such as Ext3).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) CacheFiles uses a userspace daemon to do some of the cache management - such as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) reaping stale nodes and culling. This is called cachefilesd and lives in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) /sbin.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) The filesystem and data integrity of the cache are only as good as those of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) filesystem providing the backing services. Note that CacheFiles does not
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) attempt to journal anything since the journalling interfaces of the various
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) filesystems are very specific in nature.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) CacheFiles creates a misc character device - "/dev/cachefiles" - that is used
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) to communication with the daemon. Only one thing may have this open at once,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) and while it is open, a cache is at least partially in existence. The daemon
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) opens this and sends commands down it to control the cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) CacheFiles is currently limited to a single cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) CacheFiles attempts to maintain at least a certain percentage of free space on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) the filesystem, shrinking the cache by culling the objects it contains to make
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) space if necessary - see the "Cache Culling" section. This means it can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) placed on the same medium as a live set of data, and will expand to make use of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) spare space and automatically contract when the set of data requires more
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) space.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) Requirements
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) The use of CacheFiles and its daemon requires the following features to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) available in the system and in the cache filesystem:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) - dnotify.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) - extended attributes (xattrs).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) - openat() and friends.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) - bmap() support on files in the filesystem (FIBMAP ioctl).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) - The use of bmap() to detect a partial page at the end of the file.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) It is strongly recommended that the "dir_index" option is enabled on Ext3
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) filesystems being used as a cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) Configuration
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) =============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) The cache is configured by a script in /etc/cachefilesd.conf. These commands
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) set up cache ready for use. The following script commands are available:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) brun <N>%, bcull <N>%, bstop <N>%, frun <N>%, fcull <N>%, fstop <N>%
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) Configure the culling limits. Optional. See the section on culling
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) The defaults are 7% (run), 5% (cull) and 1% (stop) respectively.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) The commands beginning with a 'b' are file space (block) limits, those
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) beginning with an 'f' are file count limits.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) dir <path>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) Specify the directory containing the root of the cache. Mandatory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) tag <name>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) Specify a tag to FS-Cache to use in distinguishing multiple caches.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) Optional. The default is "CacheFiles".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) debug <mask>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) Specify a numeric bitmask to control debugging in the kernel module.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) Optional. The default is zero (all off). The following values can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) OR'd into the mask to collect various information:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) == =================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) 1 Turn on trace of function entry (_enter() macros)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) 2 Turn on trace of function exit (_leave() macros)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) 4 Turn on trace of internal debug points (_debug())
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) == =================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) This mask can also be set through sysfs, eg::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) echo 5 >/sys/modules/cachefiles/parameters/debug
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) Starting the Cache
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) ==================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) The cache is started by running the daemon. The daemon opens the cache device,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) configures the cache and tells it to begin caching. At that point the cache
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) binds to fscache and the cache becomes live.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) The daemon is run as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) /sbin/cachefilesd [-d]* [-s] [-n] [-f <configfile>]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) The flags are:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) ``-d``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) Increase the debugging level. This can be specified multiple times and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) is cumulative with itself.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) ``-s``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) Send messages to stderr instead of syslog.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) ``-n``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) Don't daemonise and go into background.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) ``-f <configfile>``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) Use an alternative configuration file rather than the default one.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) Things to Avoid
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) Do not mount other things within the cache as this will cause problems. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) kernel module contains its own very cut-down path walking facility that ignores
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) mountpoints, but the daemon can't avoid them.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) Do not create, rename or unlink files and directories in the cache while the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) cache is active, as this may cause the state to become uncertain.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) Renaming files in the cache might make objects appear to be other objects (the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) filename is part of the lookup key).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) Do not change or remove the extended attributes attached to cache files by the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) cache as this will cause the cache state management to get confused.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) Do not create files or directories in the cache, lest the cache get confused or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) serve incorrect data.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) Do not chmod files in the cache. The module creates things with minimal
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) permissions to prevent random users being able to access them directly.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) Cache Culling
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) =============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) The cache may need culling occasionally to make space. This involves
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) discarding objects from the cache that have been used less recently than
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) anything else. Culling is based on the access time of data objects. Empty
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) directories are culled if not in use.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) Cache culling is done on the basis of the percentage of blocks and the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) percentage of files available in the underlying filesystem. There are six
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) "limits":
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) brun, frun
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) If the amount of free space and the number of available files in the cache
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) rises above both these limits, then culling is turned off.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) bcull, fcull
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) If the amount of available space or the number of available files in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) cache falls below either of these limits, then culling is started.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) bstop, fstop
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) If the amount of available space or the number of available files in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) cache falls below either of these limits, then no further allocation of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) disk space or files is permitted until culling has raised things above
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) these limits again.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) These must be configured thusly::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) 0 <= bstop < bcull < brun < 100
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) 0 <= fstop < fcull < frun < 100
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) Note that these are percentages of available space and available files, and do
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) _not_ appear as 100 minus the percentage displayed by the "df" program.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) The userspace daemon scans the cache to build up a table of cullable objects.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) These are then culled in least recently used order. A new scan of the cache is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) started as soon as space is made in the table. Objects will be skipped if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) their atimes have changed or if the kernel module says it is still using them.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) Cache Structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) The CacheFiles module will create two directories in the directory it was
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) given:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) * cache/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) * graveyard/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) The active cache objects all reside in the first directory. The CacheFiles
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) kernel module moves any retired or culled objects that it can't simply unlink
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221) to the graveyard from which the daemon will actually delete them.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) The daemon uses dnotify to monitor the graveyard directory, and will delete
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) anything that appears therein.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) The module represents index objects as directories with the filename "I..." or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228) "J...". Note that the "cache/" directory is itself a special index.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) Data objects are represented as files if they have no children, or directories
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) if they do. Their filenames all begin "D..." or "E...". If represented as a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) directory, data objects will have a file in the directory called "data" that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) actually holds the data.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) Special objects are similar to data objects, except their filenames begin
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) "S..." or "T...".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) If an object has children, then it will be represented as a directory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) Immediately in the representative directory are a collection of directories
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241) named for hash values of the child object keys with an '@' prepended. Into
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242) this directory, if possible, will be placed the representations of the child
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243) objects::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) /INDEX /INDEX /INDEX /DATA FILES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246) /=========/==========/=================================/================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247) cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248) cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...DB1ry
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...N22ry
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250) cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...FP1ry
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253) If the key is so long that it exceeds NAME_MAX with the decorations added on to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254) it, then it will be cut into pieces, the first few of which will be used to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255) make a nest of directories, and the last one of which will be the objects
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256) inside the last directory. The names of the intermediate directories will have
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257) '+' prepended::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) J1223/@23/+xy...z/+kl...m/Epqr
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262) Note that keys are raw data, and not only may they exceed NAME_MAX in size,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) they may also contain things like '/' and NUL characters, and so they may not
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264) be suitable for turning directly into a filename.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) To handle this, CacheFiles will use a suitably printable filename directly and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267) "base-64" encode ones that aren't directly suitable. The two versions of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) object filenames indicate the encoding:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 269)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 270) =============== =============== ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 271) OBJECT TYPE PRINTABLE ENCODED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 272) =============== =============== ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 273) Index "I..." "J..."
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 274) Data "D..." "E..."
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 275) Special "S..." "T..."
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 276) =============== =============== ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 277)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 278) Intermediate directories are always "@" or "+" as appropriate.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 279)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 280)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 281) Each object in the cache has an extended attribute label that holds the object
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 282) type ID (required to distinguish special objects) and the auxiliary data from
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 283) the netfs. The latter is used to detect stale objects in the cache and update
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 284) or retire them.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 285)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 286)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 287) Note that CacheFiles will erase from the cache any file it doesn't recognise or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 288) any file of an incorrect type (such as a FIFO file or a device file).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 289)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 290)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 291) Security Model and SELinux
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 292) ==========================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 293)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 294) CacheFiles is implemented to deal properly with the LSM security features of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 295) the Linux kernel and the SELinux facility.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 296)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 297) One of the problems that CacheFiles faces is that it is generally acting on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 298) behalf of a process, and running in that process's context, and that includes a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 299) security context that is not appropriate for accessing the cache - either
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 300) because the files in the cache are inaccessible to that process, or because if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 301) the process creates a file in the cache, that file may be inaccessible to other
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 302) processes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 303)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 304) The way CacheFiles works is to temporarily change the security context (fsuid,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 305) fsgid and actor security label) that the process acts as - without changing the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 306) security context of the process when it the target of an operation performed by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 307) some other process (so signalling and suchlike still work correctly).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 308)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 309)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 310) When the CacheFiles module is asked to bind to its cache, it:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 311)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 312) (1) Finds the security label attached to the root cache directory and uses
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 313) that as the security label with which it will create files. By default,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 314) this is::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 315)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 316) cachefiles_var_t
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 317)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 318) (2) Finds the security label of the process which issued the bind request
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 319) (presumed to be the cachefilesd daemon), which by default will be::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 320)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 321) cachefilesd_t
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 322)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 323) and asks LSM to supply a security ID as which it should act given the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 324) daemon's label. By default, this will be::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 325)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 326) cachefiles_kernel_t
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 327)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 328) SELinux transitions the daemon's security ID to the module's security ID
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 329) based on a rule of this form in the policy::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 330)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 331) type_transition <daemon's-ID> kernel_t : process <module's-ID>;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 332)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 333) For instance::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 334)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 335) type_transition cachefilesd_t kernel_t : process cachefiles_kernel_t;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 336)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 337)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 338) The module's security ID gives it permission to create, move and remove files
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 339) and directories in the cache, to find and access directories and files in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 340) cache, to set and access extended attributes on cache objects, and to read and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 341) write files in the cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 342)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 343) The daemon's security ID gives it only a very restricted set of permissions: it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 344) may scan directories, stat files and erase files and directories. It may
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 345) not read or write files in the cache, and so it is precluded from accessing the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 346) data cached therein; nor is it permitted to create new files in the cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 347)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 348)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 349) There are policy source files available in:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 350)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 351) https://people.redhat.com/~dhowells/fscache/cachefilesd-0.8.tar.bz2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 352)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 353) and later versions. In that tarball, see the files::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 354)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 355) cachefilesd.te
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 356) cachefilesd.fc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 357) cachefilesd.if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 358)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 359) They are built and installed directly by the RPM.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 360)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 361) If a non-RPM based system is being used, then copy the above files to their own
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 362) directory and run::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 363)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 364) make -f /usr/share/selinux/devel/Makefile
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 365) semodule -i cachefilesd.pp
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 366)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 367) You will need checkpolicy and selinux-policy-devel installed prior to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 368) build.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 369)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 370)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 371) By default, the cache is located in /var/fscache, but if it is desirable that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 372) it should be elsewhere, than either the above policy files must be altered, or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 373) an auxiliary policy must be installed to label the alternate location of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 374) cache.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 375)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 376) For instructions on how to add an auxiliary policy to enable the cache to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 377) located elsewhere when SELinux is in enforcing mode, please see::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 378)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 379) /usr/share/doc/cachefilesd-*/move-cache.txt
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 380)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 381) When the cachefilesd rpm is installed; alternatively, the document can be found
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 382) in the sources.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 383)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 384)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 385) A Note on Security
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 386) ==================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 387)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 388) CacheFiles makes use of the split security in the task_struct. It allocates
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 389) its own task_security structure, and redirects current->cred to point to it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 390) when it acts on behalf of another process, in that process's context.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 391)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 392) The reason it does this is that it calls vfs_mkdir() and suchlike rather than
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 393) bypassing security and calling inode ops directly. Therefore the VFS and LSM
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 394) may deny the CacheFiles access to the cache data because under some
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 395) circumstances the caching code is running in the security context of whatever
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 396) process issued the original syscall on the netfs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 397)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 398) Furthermore, should CacheFiles create a file or directory, the security
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 399) parameters with that object is created (UID, GID, security label) would be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 400) derived from that process that issued the system call, thus potentially
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 401) preventing other processes from accessing the cache - including CacheFiles's
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 402) cache management daemon (cachefilesd).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 403)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 404) What is required is to temporarily override the security of the process that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 405) issued the system call. We can't, however, just do an in-place change of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 406) security data as that affects the process as an object, not just as a subject.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 407) This means it may lose signals or ptrace events for example, and affects what
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 408) the process looks like in /proc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 409)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 410) So CacheFiles makes use of a logical split in the security between the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 411) objective security (task->real_cred) and the subjective security (task->cred).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 412) The objective security holds the intrinsic security properties of a process and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 413) is never overridden. This is what appears in /proc, and is what is used when a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 414) process is the target of an operation by some other process (SIGKILL for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 415) example).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 416)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 417) The subjective security holds the active security properties of a process, and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 418) may be overridden. This is not seen externally, and is used whan a process
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 419) acts upon another object, for example SIGKILLing another process or opening a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 420) file.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 421)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 422) LSM hooks exist that allow SELinux (or Smack or whatever) to reject a request
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 423) for CacheFiles to run in a context of a specific security label, or to create
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 424) files and directories with another security label.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 425)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 426)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 427) Statistical Information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 428) =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 429)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 430) If FS-Cache is compiled with the following option enabled::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 431)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 432) CONFIG_CACHEFILES_HISTOGRAM=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 433)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 434) then it will gather certain statistics and display them through a proc file.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 435)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 436) /proc/fs/cachefiles/histogram
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 437)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 438) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 439)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 440) cat /proc/fs/cachefiles/histogram
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 441) JIFS SECS LOOKUPS MKDIRS CREATES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 442) ===== ===== ========= ========= =========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 443)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 444) This shows the breakdown of the number of times each amount of time
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 445) between 0 jiffies and HZ-1 jiffies a variety of tasks took to run. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 446) columns are as follows:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 447)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 448) ======= =======================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 449) COLUMN TIME MEASUREMENT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 450) ======= =======================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 451) LOOKUPS Length of time to perform a lookup on the backing fs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 452) MKDIRS Length of time to perform a mkdir on the backing fs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 453) CREATES Length of time to perform a create on the backing fs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 454) ======= =======================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 455)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 456) Each row shows the number of events that took a particular range of times.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 457) Each step is 1 jiffy in size. The JIFS column indicates the particular
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 458) jiffy range covered, and the SECS field the equivalent number of seconds.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 459)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 460)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 461) Debugging
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 462) =========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 463)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 464) If CONFIG_CACHEFILES_DEBUG is enabled, the CacheFiles facility can have runtime
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 465) debugging enabled by adjusting the value in::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 466)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 467) /sys/module/cachefiles/parameters/debug
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 468)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 469) This is a bitmask of debugging streams to enable:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 470)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 471) ======= ======= =============================== =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 472) BIT VALUE STREAM POINT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 473) ======= ======= =============================== =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 474) 0 1 General Function entry trace
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 475) 1 2 Function exit trace
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 476) 2 4 General
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 477) ======= ======= =============================== =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 478)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 479) The appropriate set of values should be OR'd together and the result written to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 480) the control file. For example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 481)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 482) echo $((1|4|8)) >/sys/module/cachefiles/parameters/debug
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 483)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 484) will turn on all function entry debugging.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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