diff options
| -rw-r--r-- | Documentation/filesystems/caching/cachefiles.rst (renamed from Documentation/filesystems/caching/cachefiles.txt) | 139 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/index.rst | 1 | ||||
| -rw-r--r-- | MAINTAINERS | 2 | ||||
| -rw-r--r-- | fs/cachefiles/Kconfig | 4 |
4 files changed, 65 insertions, 81 deletions
diff --git a/Documentation/filesystems/caching/cachefiles.txt b/Documentation/filesystems/caching/cachefiles.rst index 28aefcbb1442..65d3db476765 100644 --- a/Documentation/filesystems/caching/cachefiles.txt +++ b/Documentation/filesystems/caching/cachefiles.rst @@ -1,8 +1,10 @@ - =============================================== - CacheFiles: CACHE ON ALREADY MOUNTED FILESYSTEM - =============================================== +.. SPDX-License-Identifier: GPL-2.0 -Contents: +=============================================== +CacheFiles: CACHE ON ALREADY MOUNTED FILESYSTEM +=============================================== + +.. Contents: (*) Overview. @@ -27,8 +29,8 @@ Contents: (*) Debugging. -======== -OVERVIEW + +Overview ======== CacheFiles is a caching backend that's meant to use as a cache a directory on @@ -58,8 +60,8 @@ spare space and automatically contract when the set of data requires more space. -============ -REQUIREMENTS + +Requirements ============ The use of CacheFiles and its daemon requires the following features to be @@ -79,84 +81,70 @@ It is strongly recommended that the "dir_index" option is enabled on Ext3 filesystems being used as a cache. -============= -CONFIGURATION +Configuration ============= The cache is configured by a script in /etc/cachefilesd.conf. These commands set up cache ready for use. The following script commands are available: - (*) brun <N>% - (*) bcull <N>% - (*) bstop <N>% - (*) frun <N>% - (*) fcull <N>% - (*) fstop <N>% - + brun <N>%, bcull <N>%, bstop <N>%, frun <N>%, fcull <N>%, fstop <N>% Configure the culling limits. Optional. See the section on culling The defaults are 7% (run), 5% (cull) and 1% (stop) respectively. The commands beginning with a 'b' are file space (block) limits, those beginning with an 'f' are file count limits. - (*) dir <path> - + dir <path> Specify the directory containing the root of the cache. Mandatory. - (*) tag <name> - + tag <name> Specify a tag to FS-Cache to use in distinguishing multiple caches. Optional. The default is "CacheFiles". - (*) debug <mask> - + debug <mask> Specify a numeric bitmask to control debugging in the kernel module. Optional. The default is zero (all off). The following values can be OR'd into the mask to collect various information: + == ================================================= 1 Turn on trace of function entry (_enter() macros) 2 Turn on trace of function exit (_leave() macros) 4 Turn on trace of internal debug points (_debug()) + == ================================================= - This mask can also be set through sysfs, eg: + This mask can also be set through sysfs, eg:: echo 5 >/sys/modules/cachefiles/parameters/debug -================== -STARTING THE CACHE +Starting the Cache ================== The cache is started by running the daemon. The daemon opens the cache device, configures the cache and tells it to begin caching. At that point the cache binds to fscache and the cache becomes live. -The daemon is run as follows: +The daemon is run as follows:: /sbin/cachefilesd [-d]* [-s] [-n] [-f <configfile>] The flags are: - (*) -d - + ``-d`` Increase the debugging level. This can be specified multiple times and is cumulative with itself. - (*) -s - + ``-s`` Send messages to stderr instead of syslog. - (*) -n - + ``-n`` Don't daemonise and go into background. - (*) -f <configfile> - + ``-f <configfile>`` Use an alternative configuration file rather than the default one. -=============== -THINGS TO AVOID +Things to Avoid =============== Do not mount other things within the cache as this will cause problems. The @@ -179,8 +167,7 @@ Do not chmod files in the cache. The module creates things with minimal permissions to prevent random users being able to access them directly. -============= -CACHE CULLING +Cache Culling ============= The cache may need culling occasionally to make space. This involves @@ -192,27 +179,21 @@ Cache culling is done on the basis of the percentage of blocks and the percentage of files available in the underlying filesystem. There are six "limits": - (*) brun - (*) frun - + brun, frun If the amount of free space and the number of available files in the cache rises above both these limits, then culling is turned off. - (*) bcull - (*) fcull - + bcull, fcull If the amount of available space or the number of available files in the cache falls below either of these limits, then culling is started. - (*) bstop - (*) fstop - + bstop, fstop If the amount of available space or the number of available files in the cache falls below either of these limits, then no further allocation of disk space or files is permitted until culling has raised things above these limits again. -These must be configured thusly: +These must be configured thusly:: 0 <= bstop < bcull < brun < 100 0 <= fstop < fcull < frun < 100 @@ -226,16 +207,14 @@ started as soon as space is made in the table. Objects will be skipped if their atimes have changed or if the kernel module says it is still using them. -=============== -CACHE STRUCTURE +Cache Structure =============== The CacheFiles module will create two directories in the directory it was given: - (*) cache/ - - (*) graveyard/ + * cache/ + * graveyard/ The active cache objects all reside in the first directory. The CacheFiles kernel module moves any retired or culled objects that it can't simply unlink @@ -261,10 +240,10 @@ If an object has children, then it will be represented as a directory. Immediately in the representative directory are a collection of directories named for hash values of the child object keys with an '@' prepended. Into this directory, if possible, will be placed the representations of the child -objects: +objects:: - INDEX INDEX INDEX DATA FILES - ========= ========== ================================= ================ + /INDEX /INDEX /INDEX /DATA FILES + /=========/==========/=================================/================ cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400 cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...DB1ry cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...N22ry @@ -275,7 +254,7 @@ If the key is so long that it exceeds NAME_MAX with the decorations added on to it, then it will be cut into pieces, the first few of which will be used to make a nest of directories, and the last one of which will be the objects inside the last directory. The names of the intermediate directories will have -'+' prepended: +'+' prepended:: J1223/@23/+xy...z/+kl...m/Epqr @@ -288,11 +267,13 @@ To handle this, CacheFiles will use a suitably printable filename directly and "base-64" encode ones that aren't directly suitable. The two versions of object filenames indicate the encoding: + =============== =============== =============== OBJECT TYPE PRINTABLE ENCODED =============== =============== =============== Index "I..." "J..." Data "D..." "E..." Special "S..." "T..." + =============== =============== =============== Intermediate directories are always "@" or "+" as appropriate. @@ -307,8 +288,7 @@ Note that CacheFiles will erase from the cache any file it doesn't recognise or any file of an incorrect type (such as a FIFO file or a device file). -========================== -SECURITY MODEL AND SELINUX +Security Model and SELinux ========================== CacheFiles is implemented to deal properly with the LSM security features of @@ -331,26 +311,26 @@ When the CacheFiles module is asked to bind to its cache, it: (1) Finds the security label attached to the root cache directory and uses that as the security label with which it will create files. By default, - this is: + this is:: cachefiles_var_t (2) Finds the security label of the process which issued the bind request - (presumed to be the cachefilesd daemon), which by default will be: + (presumed to be the cachefilesd daemon), which by default will be:: cachefilesd_t and asks LSM to supply a security ID as which it should act given the - daemon's label. By default, this will be: + daemon's label. By default, this will be:: cachefiles_kernel_t SELinux transitions the daemon's security ID to the module's security ID - based on a rule of this form in the policy. + based on a rule of this form in the policy:: type_transition <daemon's-ID> kernel_t : process <module's-ID>; - For instance: + For instance:: type_transition cachefilesd_t kernel_t : process cachefiles_kernel_t; @@ -370,7 +350,7 @@ There are policy source files available in: http://people.redhat.com/~dhowells/fscache/cachefilesd-0.8.tar.bz2 -and later versions. In that tarball, see the files: +and later versions. In that tarball, see the files:: cachefilesd.te cachefilesd.fc @@ -379,7 +359,7 @@ and later versions. In that tarball, see the files: They are built and installed directly by the RPM. If a non-RPM based system is being used, then copy the above files to their own -directory and run: +directory and run:: make -f /usr/share/selinux/devel/Makefile semodule -i cachefilesd.pp @@ -394,7 +374,7 @@ an auxiliary policy must be installed to label the alternate location of the cache. For instructions on how to add an auxiliary policy to enable the cache to be -located elsewhere when SELinux is in enforcing mode, please see: +located elsewhere when SELinux is in enforcing mode, please see:: /usr/share/doc/cachefilesd-*/move-cache.txt @@ -402,8 +382,7 @@ When the cachefilesd rpm is installed; alternatively, the document can be found in the sources. -================== -A NOTE ON SECURITY +A Note on Security ================== CacheFiles makes use of the split security in the task_struct. It allocates @@ -445,17 +424,18 @@ for CacheFiles to run in a context of a specific security label, or to create files and directories with another security label. -======================= -STATISTICAL INFORMATION +Statistical Information ======================= -If FS-Cache is compiled with the following option enabled: +If FS-Cache is compiled with the following option enabled:: CONFIG_CACHEFILES_HISTOGRAM=y then it will gather certain statistics and display them through a proc file. - (*) /proc/fs/cachefiles/histogram + /proc/fs/cachefiles/histogram + + :: cat /proc/fs/cachefiles/histogram JIFS SECS LOOKUPS MKDIRS CREATES @@ -465,36 +445,39 @@ then it will gather certain statistics and display them through a proc file. between 0 jiffies and HZ-1 jiffies a variety of tasks took to run. The columns are as follows: + ======= ======================================================= COLUMN TIME MEASUREMENT ======= ======================================================= LOOKUPS Length of time to perform a lookup on the backing fs MKDIRS Length of time to perform a mkdir on the backing fs CREATES Length of time to perform a create on the backing fs + ======= ======================================================= Each row shows the number of events that took a particular range of times. Each step is 1 jiffy in size. The JIFS column indicates the particular jiffy range covered, and the SECS field the equivalent number of seconds. -========= -DEBUGGING +Debugging ========= If CONFIG_CACHEFILES_DEBUG is enabled, the CacheFiles facility can have runtime -debugging enabled by adjusting the value in: +debugging enabled by adjusting the value in:: /sys/module/cachefiles/parameters/debug This is a bitmask of debugging streams to enable: + ======= ======= =============================== ======================= BIT VALUE STREAM POINT ======= ======= =============================== ======================= 0 1 General Function entry trace 1 2 Function exit trace 2 4 General + ======= ======= =============================== ======================= The appropriate set of values should be OR'd together and the result written to -the control file. For example: +the control file. For example:: echo $((1|4|8)) >/sys/module/cachefiles/parameters/debug diff --git a/Documentation/filesystems/caching/index.rst b/Documentation/filesystems/caching/index.rst index 75492b7c8ea0..a2cf35f89e28 100644 --- a/Documentation/filesystems/caching/index.rst +++ b/Documentation/filesystems/caching/index.rst @@ -8,5 +8,6 @@ Filesystem Caching fscache object + cachefiles netfs-api operations diff --git a/MAINTAINERS b/MAINTAINERS index 82e4b0a0c921..a103117dec85 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3731,7 +3731,7 @@ CACHEFILES: FS-CACHE BACKEND FOR CACHING ON MOUNTED FILESYSTEMS M: David Howells <dhowells@redhat.com> L: linux-cachefs@redhat.com (moderated for non-subscribers) S: Supported -F: Documentation/filesystems/caching/cachefiles.txt +F: Documentation/filesystems/caching/cachefiles.rst F: fs/cachefiles/ CADENCE MIPI-CSI2 BRIDGES diff --git a/fs/cachefiles/Kconfig b/fs/cachefiles/Kconfig index ae559ed5b3b3..ff9ca55a9ae9 100644 --- a/fs/cachefiles/Kconfig +++ b/fs/cachefiles/Kconfig @@ -8,7 +8,7 @@ config CACHEFILES filesystems - primarily networking filesystems - thus allowing fast local disk to enhance the speed of slower devices. - See Documentation/filesystems/caching/cachefiles.txt for more + See Documentation/filesystems/caching/cachefiles.rst for more information. config CACHEFILES_DEBUG @@ -36,5 +36,5 @@ config CACHEFILES_HISTOGRAM bouncing between CPUs. On the other hand, the histogram may be useful for debugging purposes. Saying 'N' here is recommended. - See Documentation/filesystems/caching/cachefiles.txt for more + See Documentation/filesystems/caching/cachefiles.rst for more information. |