Lines Matching full:cache
4 Cache on Already Mounted Filesystem
15 (*) Starting the cache.
19 (*) Cache culling.
21 (*) Cache structure.
37 CacheFiles is a caching backend that's meant to use as a cache a directory on
40 CacheFiles uses a userspace daemon to do some of the cache management - such as
44 The filesystem and data integrity of the cache are only as good as those of the
51 and while it is open, a cache is at least partially in existence. The daemon
52 opens this and sends commands down it to control the cache.
54 CacheFiles is currently limited to a single cache.
57 the filesystem, shrinking the cache by culling the objects it contains to make
58 space if necessary - see the "Cache Culling" section. This means it can be
69 available in the system and in the cache filesystem:
82 filesystems being used as a cache.
88 The cache is configured by a script in /etc/cachefilesd.conf. These commands
89 set up cache ready for use. The following script commands are available:
99 Specify the directory containing the root of the cache. Mandatory.
102 Specify a tag to FS-Cache to use in distinguishing multiple caches.
121 Starting the Cache
124 The cache is started by running the daemon. The daemon opens the cache device,
125 configures the cache and tells it to begin caching. At that point the cache
126 binds to fscache and the cache becomes live.
151 Do not mount other things within the cache as this will cause problems. The
155 Do not create, rename or unlink files and directories in the cache while the
156 cache is active, as this may cause the state to become uncertain.
158 Renaming files in the cache might make objects appear to be other objects (the
161 Do not change or remove the extended attributes attached to cache files by the
162 cache as this will cause the cache state management to get confused.
164 Do not create files or directories in the cache, lest the cache get confused or
167 Do not chmod files in the cache. The module creates things with minimal
171 Cache Culling
174 The cache may need culling occasionally to make space. This involves
175 discarding objects from the cache that have been used less recently than
179 Cache culling is done on the basis of the percentage of blocks and the
184 If the amount of free space and the number of available files in the cache
189 cache falls below either of these limits, then culling is started.
193 cache falls below either of these limits, then no further allocation of
205 The userspace daemon scans the cache to build up a table of cullable objects.
206 These are then culled in least recently used order. A new scan of the cache is
211 Cache Structure
217 * cache/
220 The active cache objects all reside in the first directory. The CacheFiles
229 "J...". Note that the "cache/" directory is itself a special index.
248 cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400
249 cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...DB1ry
250 cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...N22ry
251 cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...FP1ry
282 Each object in the cache has an extended attribute label that holds the object
284 the netfs. The latter is used to detect stale objects in the cache and update
288 Note that CacheFiles will erase from the cache any file it doesn't recognise or
300 security context that is not appropriate for accessing the cache - either
301 because the files in the cache are inaccessible to that process, or because if
302 the process creates a file in the cache, that file may be inaccessible to other
311 When the CacheFiles module is asked to bind to its cache, it:
313 (1) Finds the security label attached to the root cache directory and uses
340 and directories in the cache, to find and access directories and files in the
341 cache, to set and access extended attributes on cache objects, and to read and
342 write files in the cache.
346 not read or write files in the cache, and so it is precluded from accessing the
347 data cached therein; nor is it permitted to create new files in the cache.
372 By default, the cache is located in /var/fscache, but if it is desirable that
375 cache.
377 For instructions on how to add an auxiliary policy to enable the cache to be
380 /usr/share/doc/cachefilesd-*/move-cache.txt
395 may deny the CacheFiles access to the cache data because under some
402 preventing other processes from accessing the cache - including CacheFiles's
403 cache management daemon (cachefilesd).
431 If FS-Cache is compiled with the following option enabled::
491 When working in its original mode, CacheFiles serves as a local cache for a
496 The essential difference between these two modes is seen when a cache miss
498 server and then write it to the cache file; in on-demand read mode, fetching
499 the data and writing it into the cache is delegated to a user daemon.
538 * ``object_id`` is a unique ID identifying the cache file operated on.
561 When the netfs opens a cache file for the first time, a request with the
583 * ``fd`` indicates an anonymous fd referring to the cache file, through
585 cache file.
589 the requested cache file. With the given anonymous fd, the user daemon can
590 fetch the data and write it to the cache file in the background, even when
591 kernel has not triggered a cache miss yet.
593 Be noted that each cache file has a unique object_id, while it may have multiple
613 * When >= 0, ``cache_size`` indicates the size of the cache file;
630 When a cache miss is encountered in on-demand read mode, CacheFiles will send a
648 and write it to the cache file identified by object_id.