Commit 9dc8d9bf authored by David Howells's avatar David Howells
Browse files

CacheFiles: Implement invalidation 



Implement invalidation for CacheFiles.  This is in two parts:

 (1) Provide an invalidation method (which just truncates the backing file).

 (2) Abort attempts to copy anything read from the backing file whilst
     invalidation is in progress.

Question: CacheFiles uses truncation in a couple of places.  It has been using
notify_change() rather than sys_truncate() or something similar.  This means
it bypasses a bunch of checks and suchlike that it possibly should be making
(security, file locking, lease breaking, vfsmount write).  Should it be using
vfs_truncate() as added by a preceding patch or should it use notify_write()
and assume that anyone poking around in the cache files on disk gets
everything they deserve?

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent a02de960

fs/cachefiles/interface.c

+49 −0
Original line number Diff line number Diff line
@@ -440,6 +440,54 @@ truncate_failed: 
	return ret;

}



/*

 * Invalidate an object

 */

static void cachefiles_invalidate_object(struct fscache_operation *op)

{

	struct cachefiles_object *object;

	struct cachefiles_cache *cache;

	const struct cred *saved_cred;

	struct path path;

	uint64_t ni_size;

	int ret;



	object = container_of(op->object, struct cachefiles_object, fscache);

	cache = container_of(object->fscache.cache,

			     struct cachefiles_cache, cache);



	op->object->cookie->def->get_attr(op->object->cookie->netfs_data,

					  &ni_size);



	_enter("{OBJ%x},[%llu]",

	       op->object->debug_id, (unsigned long long)ni_size);



	if (object->backer) {

		ASSERT(S_ISREG(object->backer->d_inode->i_mode));



		fscache_set_store_limit(&object->fscache, ni_size);



		path.dentry = object->backer;

		path.mnt = cache->mnt;



		cachefiles_begin_secure(cache, &saved_cred);

		ret = vfs_truncate(&path, 0);

		if (ret == 0)

			ret = vfs_truncate(&path, ni_size);

		cachefiles_end_secure(cache, saved_cred);



		if (ret != 0) {

			fscache_set_store_limit(&object->fscache, 0);

			if (ret == -EIO)

				cachefiles_io_error_obj(object,

							"Invalidate failed");

		}

	}



	fscache_op_complete(op);

	_leave("");

}



/*

 * dissociate a cache from all the pages it was backing

 */
@@ -455,6 +503,7 @@ const struct fscache_cache_ops cachefiles_cache_ops = { 
	.lookup_complete	= cachefiles_lookup_complete,

	.grab_object		= cachefiles_grab_object,

	.update_object		= cachefiles_update_object,

	.invalidate_object	= cachefiles_invalidate_object,

	.drop_object		= cachefiles_drop_object,

	.put_object		= cachefiles_put_object,

	.sync_cache		= cachefiles_sync_cache,

fs/cachefiles/rdwr.c

+4 −1
Original line number Diff line number Diff line
@@ -174,7 +174,10 @@ static void cachefiles_read_copier(struct fscache_operation *_op) 
		_debug("- copy {%lu}", monitor->back_page->index);



	recheck:

		if (PageUptodate(monitor->back_page)) {

		if (test_bit(FSCACHE_COOKIE_INVALIDATING,

			     &object->fscache.cookie->flags)) {

			error = -ESTALE;

		} else if (PageUptodate(monitor->back_page)) {

			copy_highpage(monitor->netfs_page, monitor->back_page);

			fscache_mark_page_cached(monitor->op,

						 monitor->netfs_page);

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