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authorDavid Howells2012-12-20 15:52:36 -0600
committerDavid Howells2012-12-20 16:04:07 -0600
commitef778e7ae67cd426c30cad43378b908f5eb0bad5 (patch)
tree4893f19487cb99e8ec0eb835ec4391d952641a9c /Documentation
parent9f10523f891928330b7529da54c1a3cc65180b1a (diff)
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FS-Cache: Provide proper invalidation
Provide a proper invalidation method rather than relying on the netfs retiring the cookie it has and getting a new one. The problem with this is that isn't easy for the netfs to make sure that it has completed/cancelled all its outstanding storage and retrieval operations on the cookie it is retiring. Instead, have the cache provide an invalidation method that will cancel or wait for all currently outstanding operations before invalidating the cache, and will cause new operations to queue up behind that. Whilst invalidation is in progress, some requests will be rejected until the cache can stack a barrier on the operation queue to cause new operations to be deferred behind it. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/caching/backend-api.txt12
-rw-r--r--Documentation/filesystems/caching/netfs-api.txt46
-rw-r--r--Documentation/filesystems/caching/object.txt23
3 files changed, 65 insertions, 16 deletions
diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
index f4769b9399df..d78bab9622c6 100644
--- a/Documentation/filesystems/caching/backend-api.txt
+++ b/Documentation/filesystems/caching/backend-api.txt
@@ -308,6 +308,18 @@ performed on the denizens of the cache. These are held in a structure of type:
308 obtained by calling object->cookie->def->get_aux()/get_attr(). 308 obtained by calling object->cookie->def->get_aux()/get_attr().
309 309
310 310
311 (*) Invalidate data object [mandatory]:
312
313 int (*invalidate_object)(struct fscache_operation *op)
314
315 This is called to invalidate a data object (as pointed to by op->object).
316 All the data stored for this object should be discarded and an
317 attr_changed operation should be performed. The caller will follow up
318 with an object update operation.
319
320 fscache_op_complete() must be called on op before returning.
321
322
311 (*) Discard object [mandatory]: 323 (*) Discard object [mandatory]:
312 324
313 void (*drop_object)(struct fscache_object *object) 325 void (*drop_object)(struct fscache_object *object)
diff --git a/Documentation/filesystems/caching/netfs-api.txt b/Documentation/filesystems/caching/netfs-api.txt
index 7cc6bf2871eb..97e6c0ecc5ef 100644
--- a/Documentation/filesystems/caching/netfs-api.txt
+++ b/Documentation/filesystems/caching/netfs-api.txt
@@ -35,8 +35,9 @@ This document contains the following sections:
35 (12) Index and data file update 35 (12) Index and data file update
36 (13) Miscellaneous cookie operations 36 (13) Miscellaneous cookie operations
37 (14) Cookie unregistration 37 (14) Cookie unregistration
38 (15) Index and data file invalidation 38 (15) Index invalidation
39 (16) FS-Cache specific page flags. 39 (16) Data file invalidation
40 (17) FS-Cache specific page flags.
40 41
41 42
42============================= 43=============================
@@ -767,13 +768,42 @@ the cookies for "child" indices, objects and pages have been relinquished
767first. 768first.
768 769
769 770
770================================ 771==================
771INDEX AND DATA FILE INVALIDATION 772INDEX INVALIDATION
772================================ 773==================
774
775There is no direct way to invalidate an index subtree. To do this, the caller
776should relinquish and retire the cookie they have, and then acquire a new one.
777
778
779======================
780DATA FILE INVALIDATION
781======================
782
783Sometimes it will be necessary to invalidate an object that contains data.
784Typically this will be necessary when the server tells the netfs of a foreign
785change - at which point the netfs has to throw away all the state it had for an
786inode and reload from the server.
787
788To indicate that a cache object should be invalidated, the following function
789can be called:
790
791 void fscache_invalidate(struct fscache_cookie *cookie);
792
793This can be called with spinlocks held as it defers the work to a thread pool.
794All extant storage, retrieval and attribute change ops at this point are
795cancelled and discarded. Some future operations will be rejected until the
796cache has had a chance to insert a barrier in the operations queue. After
797that, operations will be queued again behind the invalidation operation.
798
799The invalidation operation will perform an attribute change operation and an
800auxiliary data update operation as it is very likely these will have changed.
801
802Using the following function, the netfs can wait for the invalidation operation
803to have reached a point at which it can start submitting ordinary operations
804once again:
773 805
774There is no direct way to invalidate an index subtree or a data file. To do 806 void fscache_wait_on_invalidate(struct fscache_cookie *cookie);
775this, the caller should relinquish and retire the cookie they have, and then
776acquire a new one.
777 807
778 808
779=========================== 809===========================
diff --git a/Documentation/filesystems/caching/object.txt b/Documentation/filesystems/caching/object.txt
index 58313348da87..100ff41127e4 100644
--- a/Documentation/filesystems/caching/object.txt
+++ b/Documentation/filesystems/caching/object.txt
@@ -216,7 +216,14 @@ servicing netfs requests:
216 The normal running state. In this state, requests the netfs makes will be 216 The normal running state. In this state, requests the netfs makes will be
217 passed on to the cache. 217 passed on to the cache.
218 218
219 (6) State FSCACHE_OBJECT_UPDATING. 219 (6) State FSCACHE_OBJECT_INVALIDATING.
220
221 The object is undergoing invalidation. When the state comes here, it
222 discards all pending read, write and attribute change operations as it is
223 going to clear out the cache entirely and reinitialise it. It will then
224 continue to the FSCACHE_OBJECT_UPDATING state.
225
226 (7) State FSCACHE_OBJECT_UPDATING.
220 227
221 The state machine comes here to update the object in the cache from the 228 The state machine comes here to update the object in the cache from the
222 netfs's records. This involves updating the auxiliary data that is used 229 netfs's records. This involves updating the auxiliary data that is used
@@ -225,13 +232,13 @@ servicing netfs requests:
225And there are terminal states in which an object cleans itself up, deallocates 232And there are terminal states in which an object cleans itself up, deallocates
226memory and potentially deletes stuff from disk: 233memory and potentially deletes stuff from disk:
227 234
228 (7) State FSCACHE_OBJECT_LC_DYING. 235 (8) State FSCACHE_OBJECT_LC_DYING.
229 236
230 The object comes here if it is dying because of a lookup or creation 237 The object comes here if it is dying because of a lookup or creation
231 error. This would be due to a disk error or system error of some sort. 238 error. This would be due to a disk error or system error of some sort.
232 Temporary data is cleaned up, and the parent is released. 239 Temporary data is cleaned up, and the parent is released.
233 240
234 (8) State FSCACHE_OBJECT_DYING. 241 (9) State FSCACHE_OBJECT_DYING.
235 242
236 The object comes here if it is dying due to an error, because its parent 243 The object comes here if it is dying due to an error, because its parent
237 cookie has been relinquished by the netfs or because the cache is being 244 cookie has been relinquished by the netfs or because the cache is being
@@ -241,27 +248,27 @@ memory and potentially deletes stuff from disk:
241 can destroy themselves. This object waits for all its children to go away 248 can destroy themselves. This object waits for all its children to go away
242 before advancing to the next state. 249 before advancing to the next state.
243 250
244 (9) State FSCACHE_OBJECT_ABORT_INIT. 251(10) State FSCACHE_OBJECT_ABORT_INIT.
245 252
246 The object comes to this state if it was waiting on its parent in 253 The object comes to this state if it was waiting on its parent in
247 FSCACHE_OBJECT_INIT, but its parent died. The object will destroy itself 254 FSCACHE_OBJECT_INIT, but its parent died. The object will destroy itself
248 so that the parent may proceed from the FSCACHE_OBJECT_DYING state. 255 so that the parent may proceed from the FSCACHE_OBJECT_DYING state.
249 256
250(10) State FSCACHE_OBJECT_RELEASING. 257(11) State FSCACHE_OBJECT_RELEASING.
251(11) State FSCACHE_OBJECT_RECYCLING. 258(12) State FSCACHE_OBJECT_RECYCLING.
252 259
253 The object comes to one of these two states when dying once it is rid of 260 The object comes to one of these two states when dying once it is rid of
254 all its children, if it is dying because the netfs relinquished its 261 all its children, if it is dying because the netfs relinquished its
255 cookie. In the first state, the cached data is expected to persist, and 262 cookie. In the first state, the cached data is expected to persist, and
256 in the second it will be deleted. 263 in the second it will be deleted.
257 264
258(12) State FSCACHE_OBJECT_WITHDRAWING. 265(13) State FSCACHE_OBJECT_WITHDRAWING.
259 266
260 The object transits to this state if the cache decides it wants to 267 The object transits to this state if the cache decides it wants to
261 withdraw the object from service, perhaps to make space, but also due to 268 withdraw the object from service, perhaps to make space, but also due to
262 error or just because the whole cache is being withdrawn. 269 error or just because the whole cache is being withdrawn.
263 270
264(13) State FSCACHE_OBJECT_DEAD. 271(14) State FSCACHE_OBJECT_DEAD.
265 272
266 The object transits to this state when the in-memory object record is 273 The object transits to this state when the in-memory object record is
267 ready to be deleted. The object processor shouldn't ever see an object in 274 ready to be deleted. The object processor shouldn't ever see an object in