filesystems/caching/backend-api.txt

20 The cache definition (struct fscache_cache) should be initialised by calling:
38 The cache should then be registered with FS-Cache by passing a pointer to the
45 Two extra arguments should also be supplied:
47  (*) "fsdef" which should point to the object representation for the FS-Cache
52  (*) "tagname" which, if given, should be a text string naming this cache.  If
138      Structures of this type should be allocated by the cache backend and
144      that refer to a particular object.  In such a case it should be printed
148      is backing.  An object should retired when put_object() is called if it is
149      in state FSCACHE_OBJECT_RECYCLING.  The fscache_object struct should be
173      an operation needs more processing time, it should be enqueued again.
192      do this, the retrieval->op.processor method pointer should be set
228      This isn't strictly an operation, but should be pointed at a string naming
238      cookie in a particular cache.  fscache_object_init() should be called on
252      allocated and attached to the cookie.  This should instantiate that object
255      The method should call fscache_object_lookup_negative() as soon as
258      fscache_obtained_object() should be called once the object is in a
260      should also be called once a non-present object has been created.
262      If a lookup error occurs, fscache_object_lookup_error() should be called
280      It should return the object pointer if successful.
307      new information should be in object->cookie->netfs_data.  This can be
316      cookie, and that the cache should release the object's resources and
319      This method should not attempt to release any references held by the
357      It should also call fscache_set_store_limit() to indicate to FS-Cache the
373      for an object and the metadata used to track it.  Zero size should be
376      This should return 0 if successful, -ENOSPC if there isn't enough space
396      If there's no page in the cache, then -ENODATA should be returned if the
400      If there is suitable data in the cache, then a read operation should be
401      queued and 0 returned.  When the read finishes, fscache_end_io() should be
404      The fscache_mark_pages_cached() should be called for the page if any cache
409      The retrieval record pointed to by op should be retained for each page
414      pool.  If this is desired, the op->op.processor should be set to point to
415      the appropriate processing routine, and fscache_enqueue_retrieval() should
420      If an I/O error occurs, fscache_io_error() should be called and -ENOBUFS
438      If there was an error such as -ENOMEM, then that should be returned; else
439      if one or more pages couldn't be read or allocated, then -ENOBUFS should
441      should be returned.  If all the pages are dispatched then 0 should be
453      It should, however, set up any internal metadata required such that
456      If there's no backing block available, then -ENOBUFS should be returned
458      allocated, then the netfs page should be marked and 0 returned.
469      nr_pages should be treated as for the read_or_alloc_pages() method.
485      If an error occurred, then a negative error code should be returned,
486      otherwise zero should be returned.  FS-Cache will take appropriate action
498      cache backend should tear down any internal representation or tracking it
526      error value should be 0 if successful and an error otherwise.
556      netfs to use.  data and datalen should specify where the auxiliary data
572 	    The coherency data indicates that the object is obsolete and should
613      produced a positive result, or that an object was created.  This should