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Subject[PATCH 09/17] CacheFiles: Implement invalidation
Date
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: David Howells <dhowells@redhat.com>
---
fs/cachefiles/interface.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
fs/cachefiles/rdwr.c | 5 ++++-
2 files changed, 53 insertions(+), 1 deletions(-)
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 9bff0f8..7a9d574 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -441,6 +441,54 @@ truncate_failed:
}

/*
+ * 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
*/
static void cachefiles_dissociate_pages(struct fscache_cache *cache)
@@ -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,
diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index 31cda81..f437e97 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -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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