diff options
Diffstat (limited to 'Documentation/filesystems/caching')
| -rw-r--r-- | Documentation/filesystems/caching/backend-api.rst (renamed from Documentation/filesystems/caching/backend-api.txt) | 165 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/cachefiles.rst (renamed from Documentation/filesystems/caching/cachefiles.txt) | 139 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/fscache.rst | 565 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/fscache.txt | 448 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/index.rst | 14 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/netfs-api.rst (renamed from Documentation/filesystems/caching/netfs-api.txt) | 172 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/object.rst (renamed from Documentation/filesystems/caching/object.txt) | 43 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/operations.rst (renamed from Documentation/filesystems/caching/operations.txt) | 45 |
8 files changed, 841 insertions, 750 deletions
diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.rst index c418280c915f..19fbf6b9aa36 100644 --- a/Documentation/filesystems/caching/backend-api.txt +++ b/Documentation/filesystems/caching/backend-api.rst @@ -1,6 +1,8 @@ - ========================== - FS-CACHE CACHE BACKEND API - ========================== +.. SPDX-License-Identifier: GPL-2.0 + +========================== +FS-Cache Cache backend API +========================== The FS-Cache system provides an API by which actual caches can be supplied to FS-Cache for it to then serve out to network filesystems and other interested @@ -9,15 +11,14 @@ parties. This API is declared in <linux/fscache-cache.h>. -==================================== -INITIALISING AND REGISTERING A CACHE +Initialising and Registering a Cache ==================================== To start off, a cache definition must be initialised and registered for each cache the backend wants to make available. For instance, CacheFS does this in the fill_super() operation on mounting. -The cache definition (struct fscache_cache) should be initialised by calling: +The cache definition (struct fscache_cache) should be initialised by calling:: void fscache_init_cache(struct fscache_cache *cache, struct fscache_cache_ops *ops, @@ -26,17 +27,17 @@ The cache definition (struct fscache_cache) should be initialised by calling: Where: - (*) "cache" is a pointer to the cache definition; + * "cache" is a pointer to the cache definition; - (*) "ops" is a pointer to the table of operations that the backend supports on + * "ops" is a pointer to the table of operations that the backend supports on this cache; and - (*) "idfmt" is a format and printf-style arguments for constructing a label + * "idfmt" is a format and printf-style arguments for constructing a label for the cache. The cache should then be registered with FS-Cache by passing a pointer to the -previously initialised cache definition to: +previously initialised cache definition to:: int fscache_add_cache(struct fscache_cache *cache, struct fscache_object *fsdef, @@ -44,12 +45,12 @@ previously initialised cache definition to: Two extra arguments should also be supplied: - (*) "fsdef" which should point to the object representation for the FS-Cache + * "fsdef" which should point to the object representation for the FS-Cache master index in this cache. Netfs primary index entries will be created here. FS-Cache keeps the caller's reference to the index object if successful and will release it upon withdrawal of the cache. - (*) "tagname" which, if given, should be a text string naming this cache. If + * "tagname" which, if given, should be a text string naming this cache. If this is NULL, the identifier will be used instead. For CacheFS, the identifier is set to name the underlying block device and the tag can be supplied by mount. @@ -58,20 +59,18 @@ This function may return -ENOMEM if it ran out of memory or -EEXIST if the tag is already in use. 0 will be returned on success. -===================== -UNREGISTERING A CACHE +Unregistering a Cache ===================== A cache can be withdrawn from the system by calling this function with a -pointer to the cache definition: +pointer to the cache definition:: void fscache_withdraw_cache(struct fscache_cache *cache); In CacheFS's case, this is called by put_super(). -======== -SECURITY +Security ======== The cache methods are executed one of two contexts: @@ -89,8 +88,7 @@ be masqueraded for the duration of the cache driver's access to the cache. This is left to the cache to handle; FS-Cache makes no effort in this regard. -=================================== -CONTROL AND STATISTICS PRESENTATION +Control and Statistics Presentation =================================== The cache may present data to the outside world through FS-Cache's interfaces @@ -101,11 +99,10 @@ is enabled. This is accessible through the kobject struct fscache_cache::kobj and is for use by the cache as it sees fit. -======================== -RELEVANT DATA STRUCTURES +Relevant Data Structures ======================== - (*) Index/Data file FS-Cache representation cookie: + * Index/Data file FS-Cache representation cookie:: struct fscache_cookie { struct fscache_object_def *def; @@ -121,7 +118,7 @@ RELEVANT DATA STRUCTURES cache operations. - (*) In-cache object representation: + * In-cache object representation:: struct fscache_object { int debug_id; @@ -150,7 +147,7 @@ RELEVANT DATA STRUCTURES initialised by calling fscache_object_init(object). - (*) FS-Cache operation record: + * FS-Cache operation record:: struct fscache_operation { atomic_t usage; @@ -173,7 +170,7 @@ RELEVANT DATA STRUCTURES an operation needs more processing time, it should be enqueued again. - (*) FS-Cache retrieval operation record: + * FS-Cache retrieval operation record:: struct fscache_retrieval { struct fscache_operation op; @@ -198,7 +195,7 @@ RELEVANT DATA STRUCTURES it sees fit. - (*) FS-Cache storage operation record: + * FS-Cache storage operation record:: struct fscache_storage { struct fscache_operation op; @@ -212,16 +209,17 @@ RELEVANT DATA STRUCTURES storage. -================ -CACHE OPERATIONS +Cache Operations ================ The cache backend provides FS-Cache with a table of operations that can be performed on the denizens of the cache. These are held in a structure of type: - struct fscache_cache_ops + :: + + struct fscache_cache_ops - (*) Name of cache provider [mandatory]: + * Name of cache provider [mandatory]:: const char *name @@ -229,7 +227,7 @@ performed on the denizens of the cache. These are held in a structure of type: the backend. - (*) Allocate a new object [mandatory]: + * Allocate a new object [mandatory]:: struct fscache_object *(*alloc_object)(struct fscache_cache *cache, struct fscache_cookie *cookie) @@ -244,7 +242,7 @@ performed on the denizens of the cache. These are held in a structure of type: form once lookup is complete or aborted. - (*) Look up and create object [mandatory]: + * Look up and create object [mandatory]:: void (*lookup_object)(struct fscache_object *object) @@ -263,7 +261,7 @@ performed on the denizens of the cache. These are held in a structure of type: to abort the lookup of that object. - (*) Release lookup data [mandatory]: + * Release lookup data [mandatory]:: void (*lookup_complete)(struct fscache_object *object) @@ -271,7 +269,7 @@ performed on the denizens of the cache. These are held in a structure of type: using to perform a lookup. - (*) Increment object refcount [mandatory]: + * Increment object refcount [mandatory]:: struct fscache_object *(*grab_object)(struct fscache_object *object) @@ -280,7 +278,7 @@ performed on the denizens of the cache. These are held in a structure of type: It should return the object pointer if successful. - (*) Lock/Unlock object [mandatory]: + * Lock/Unlock object [mandatory]:: void (*lock_object)(struct fscache_object *object) void (*unlock_object)(struct fscache_object *object) @@ -289,7 +287,7 @@ performed on the denizens of the cache. These are held in a structure of type: to schedule with the lock held, so a spinlock isn't sufficient. - (*) Pin/Unpin object [optional]: + * Pin/Unpin object [optional]:: int (*pin_object)(struct fscache_object *object) void (*unpin_object)(struct fscache_object *object) @@ -299,7 +297,7 @@ performed on the denizens of the cache. These are held in a structure of type: enough space in the cache to permit this. - (*) Check coherency state of an object [mandatory]: + * Check coherency state of an object [mandatory]:: int (*check_consistency)(struct fscache_object *object) @@ -308,7 +306,7 @@ performed on the denizens of the cache. These are held in a structure of type: if they're consistent and -ESTALE otherwise. -ENOMEM and -ERESTARTSYS may also be returned. - (*) Update object [mandatory]: + * Update object [mandatory]:: int (*update_object)(struct fscache_object *object) @@ -317,7 +315,7 @@ performed on the denizens of the cache. These are held in a structure of type: obtained by calling object->cookie->def->get_aux()/get_attr(). - (*) Invalidate data object [mandatory]: + * Invalidate data object [mandatory]:: int (*invalidate_object)(struct fscache_operation *op) @@ -329,7 +327,7 @@ performed on the denizens of the cache. These are held in a structure of type: fscache_op_complete() must be called on op before returning. - (*) Discard object [mandatory]: + * Discard object [mandatory]:: void (*drop_object)(struct fscache_object *object) @@ -341,7 +339,7 @@ performed on the denizens of the cache. These are held in a structure of type: caller. The caller will invoke the put_object() method as appropriate. - (*) Release object reference [mandatory]: + * Release object reference [mandatory]:: void (*put_object)(struct fscache_object *object) @@ -349,7 +347,7 @@ performed on the denizens of the cache. These are held in a structure of type: be freed when all the references to it are released. - (*) Synchronise a cache [mandatory]: + * Synchronise a cache [mandatory]:: void (*sync)(struct fscache_cache *cache) @@ -357,7 +355,7 @@ performed on the denizens of the cache. These are held in a structure of type: device. - (*) Dissociate a cache [mandatory]: + * Dissociate a cache [mandatory]:: void (*dissociate_pages)(struct fscache_cache *cache) @@ -365,7 +363,7 @@ performed on the denizens of the cache. These are held in a structure of type: cache withdrawal. - (*) Notification that the attributes on a netfs file changed [mandatory]: + * Notification that the attributes on a netfs file changed [mandatory]:: int (*attr_changed)(struct fscache_object *object); @@ -386,7 +384,7 @@ performed on the denizens of the cache. These are held in a structure of type: execution of this operation. - (*) Reserve cache space for an object's data [optional]: + * Reserve cache space for an object's data [optional]:: int (*reserve_space)(struct fscache_object *object, loff_t size); @@ -404,7 +402,7 @@ performed on the denizens of the cache. These are held in a structure of type: size if larger than that already. - (*) Request page be read from cache [mandatory]: + * Request page be read from cache [mandatory]:: int (*read_or_alloc_page)(struct fscache_retrieval *op, struct page *page, @@ -446,7 +444,7 @@ performed on the denizens of the cache. These are held in a structure of type: with. This will complete the operation when all pages are dealt with. - (*) Request pages be read from cache [mandatory]: + * Request pages be read from cache [mandatory]:: int (*read_or_alloc_pages)(struct fscache_retrieval *op, struct list_head *pages, @@ -457,7 +455,7 @@ performed on the denizens of the cache. These are held in a structure of type: of pages instead of one page. Any pages on which a read operation is started must be added to the page cache for the specified mapping and also to the LRU. Such pages must also be removed from the pages list and - *nr_pages decremented per page. + ``*nr_pages`` decremented per page. If there was an error such as -ENOMEM, then that should be returned; else if one or more pages couldn't be read or allocated, then -ENOBUFS should @@ -466,7 +464,7 @@ performed on the denizens of the cache. These are held in a structure of type: returned. - (*) Request page be allocated in the cache [mandatory]: + * Request page be allocated in the cache [mandatory]:: int (*allocate_page)(struct fscache_retrieval *op, struct page *page, @@ -482,7 +480,7 @@ performed on the denizens of the cache. These are held in a structure of type: allocated, then the netfs page should be marked and 0 returned. - (*) Request pages be allocated in the cache [mandatory]: + * Request pages be allocated in the cache [mandatory]:: int (*allocate_pages)(struct fscache_retrieval *op, struct list_head *pages, @@ -493,7 +491,7 @@ performed on the denizens of the cache. These are held in a structure of type: nr_pages should be treated as for the read_or_alloc_pages() method. - (*) Request page be written to cache [mandatory]: + * Request page be written to cache [mandatory]:: int (*write_page)(struct fscache_storage *op, struct page *page); @@ -514,7 +512,7 @@ performed on the denizens of the cache. These are held in a structure of type: appropriately. - (*) Discard retained per-page metadata [mandatory]: + * Discard retained per-page metadata [mandatory]:: void (*uncache_page)(struct fscache_object *object, struct page *page) @@ -523,13 +521,12 @@ performed on the denizens of the cache. These are held in a structure of type: maintains for this page. -================== -FS-CACHE UTILITIES +FS-Cache Utilities ================== FS-Cache provides some utilities that a cache backend may make use of: - (*) Note occurrence of an I/O error in a cache: + * Note occurrence of an I/O error in a cache:: void fscache_io_error(struct fscache_cache *cache) @@ -541,7 +538,7 @@ FS-Cache provides some utilities that a cache backend may make use of: This does not actually withdraw the cache. That must be done separately. - (*) Invoke the retrieval I/O completion function: + * Invoke the retrieval I/O completion function:: void fscache_end_io(struct fscache_retrieval *op, struct page *page, int error); @@ -550,8 +547,8 @@ FS-Cache provides some utilities that a cache backend may make use of: error value should be 0 if successful and an error otherwise. - (*) Record that one or more pages being retrieved or allocated have been dealt - with: + * Record that one or more pages being retrieved or allocated have been dealt + with:: void fscache_retrieval_complete(struct fscache_retrieval *op, int n_pages); @@ -562,7 +559,7 @@ FS-Cache provides some utilities that a cache backend may make use of: completed. - (*) Record operation completion: + * Record operation completion:: void fscache_op_complete(struct fscache_operation *op); @@ -571,7 +568,7 @@ FS-Cache provides some utilities that a cache backend may make use of: one or more pending operations to start running. - (*) Set highest store limit: + * Set highest store limit:: void fscache_set_store_limit(struct fscache_object *object, loff_t i_size); @@ -581,7 +578,7 @@ FS-Cache provides some utilities that a cache backend may make use of: rejected by fscache_read_alloc_page() and co with -ENOBUFS. - (*) Mark pages as being cached: + * Mark pages as being cached:: void fscache_mark_pages_cached(struct fscache_retrieval *op, struct pagevec *pagevec); @@ -590,7 +587,7 @@ FS-Cache provides some utilities that a cache backend may make use of: the netfs must call fscache_uncache_page() to unmark the pages. - (*) Perform coherency check on an object: + * Perform coherency check on an object:: enum fscache_checkaux fscache_check_aux(struct fscache_object *object, const void *data, @@ -603,29 +600,26 @@ FS-Cache provides some utilities that a cache backend may make use of: One of three values will be returned: - (*) FSCACHE_CHECKAUX_OKAY - + FSCACHE_CHECKAUX_OKAY The coherency data indicates the object is valid as is. - (*) FSCACHE_CHECKAUX_NEEDS_UPDATE - + FSCACHE_CHECKAUX_NEEDS_UPDATE The coherency data needs updating, but otherwise the object is valid. - (*) FSCACHE_CHECKAUX_OBSOLETE - + FSCACHE_CHECKAUX_OBSOLETE The coherency data indicates that the object is obsolete and should be discarded. - (*) Initialise a freshly allocated object: + * Initialise a freshly allocated object:: void fscache_object_init(struct fscache_object *object); This initialises all the fields in an object representation. - (*) Indicate the destruction of an object: + * Indicate the destruction of an object:: void fscache_object_destroyed(struct fscache_cache *cache); @@ -635,7 +629,7 @@ FS-Cache provides some utilities that a cache backend may make use of: all the objects. - (*) Indicate negative lookup on an object: + * Indicate negative lookup on an object:: void fscache_object_lookup_negative(struct fscache_object *object); @@ -650,7 +644,7 @@ FS-Cache provides some utilities that a cache backend may make use of: significant - all subsequent calls are ignored. - (*) Indicate an object has been obtained: + * Indicate an object has been obtained:: void fscache_obtained_object(struct fscache_object *object); @@ -667,7 +661,7 @@ FS-Cache provides some utilities that a cache backend may make use of: (2) that writes may now proceed against this object. - (*) Indicate that object lookup failed: + * Indicate that object lookup failed:: void fscache_object_lookup_error(struct fscache_object *object); @@ -676,7 +670,7 @@ FS-Cache provides some utilities that a cache backend may make use of: as possible. - (*) Indicate that a stale object was found and discarded: + * Indicate that a stale object was found and discarded:: void fscache_object_retrying_stale(struct fscache_object *object); @@ -685,7 +679,7 @@ FS-Cache provides some utilities that a cache backend may make use of: discarded from the cache and the lookup will be performed again. - (*) Indicate that the caching backend killed an object: + * Indicate that the caching backend killed an object:: void fscache_object_mark_killed(struct fscache_object *object, enum fscache_why_object_killed why); @@ -693,13 +687,20 @@ FS-Cache provides some utilities that a cache backend may make use of: This is called to indicate that the cache backend preemptively killed an object. The why parameter should be set to indicate the reason: - FSCACHE_OBJECT_IS_STALE - the object was stale and needs discarding. - FSCACHE_OBJECT_NO_SPACE - there was insufficient cache space - FSCACHE_OBJECT_WAS_RETIRED - the object was retired when relinquished. - FSCACHE_OBJECT_WAS_CULLED - the object was culled to make space. + FSCACHE_OBJECT_IS_STALE + - the object was stale and needs discarding. + + FSCACHE_OBJECT_NO_SPACE + - there was insufficient cache space + + FSCACHE_OBJECT_WAS_RETIRED + - the object was retired when relinquished. + + FSCACHE_OBJECT_WAS_CULLED + - the object was culled to make space. - (*) Get and release references on a retrieval record: + * Get and release references on a retrieval record:: void fscache_get_retrieval(struct fscache_retrieval *op); void fscache_put_retrieval(struct fscache_retrieval *op); @@ -708,7 +709,7 @@ FS-Cache provides some utilities that a cache backend may make use of: asynchronous data retrieval and block allocation. - (*) Enqueue a retrieval record for processing. + * Enqueue a retrieval record for processing:: void fscache_enqueue_retrieval(struct fscache_retrieval *op); @@ -718,7 +719,7 @@ FS-Cache provides some utilities that a cache backend may make use of: within the callback function. - (*) List of object state names: + * List of object state names:: const char *fscache_object_states[]; 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/fscache.rst b/Documentation/filesystems/caching/fscache.rst new file mode 100644 index 000000000000..70de86922b6a --- /dev/null +++ b/Documentation/filesystems/caching/fscache.rst @@ -0,0 +1,565 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================== +General Filesystem Caching +========================== + +Overview +======== + +This facility is a general purpose cache for network filesystems, though it +could be used for caching other things such as ISO9660 filesystems too. + +FS-Cache mediates between cache backends (such as CacheFS) and network +filesystems:: + + +---------+ + | | +--------------+ + | NFS |--+ | | |