CacheFiles: Implement interface to check cache consistency

Implement the FS-Cache interface to check the consistency of a cache object in
CacheFiles.

Original-author: Hongyi Jia <jiayisuse@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Hongyi Jia <jiayisuse@gmail.com>
cc: Milosz Tanski <milosz@adfin.com>

3 files changed, 63 insertions, 0 deletions

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index d4c1206af9fc..43eb5592cdea 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -378,6 +378,31 @@ static void cachefiles_sync_cache(struct fscache_cache *_cache)
 }
 
 /*
+ * check if the backing cache is updated to FS-Cache
+ * - called by FS-Cache when evaluates if need to invalidate the cache
+ */
+static bool cachefiles_check_consistency(struct fscache_operation *op)
+{
+        struct cachefiles_object *object;
+        struct cachefiles_cache *cache;
+        const struct cred *saved_cred;
+        int ret;
+
+        _enter("{OBJ%x}", op->object->debug_id);
+
+        object = container_of(op->object, struct cachefiles_object, fscache);
+        cache = container_of(object->fscache.cache,
+                             struct cachefiles_cache, cache);
+
+        cachefiles_begin_secure(cache, &saved_cred);
+        ret = cachefiles_check_auxdata(object);
+        cachefiles_end_secure(cache, saved_cred);
+
+        _leave(" = %d", ret);
+        return ret;
+}
+
+/*
  * notification the attributes on an object have changed
  * - called with reads/writes excluded by FS-Cache
  */
@@ -522,4 +547,5 @@ const struct fscache_cache_ops cachefiles_cache_ops = {
         .write_page             = cachefiles_write_page,
         .uncache_page           = cachefiles_uncache_page,
         .dissociate_pages       = cachefiles_dissociate_pages,
+        .check_consistency      = cachefiles_check_consistency,
 };
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 49382519907a..5349473df1b1 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -235,6 +235,7 @@ extern int cachefiles_set_object_xattr(struct cachefiles_object *object,
                                        struct cachefiles_xattr *auxdata);
 extern int cachefiles_update_object_xattr(struct cachefiles_object *object,
                                           struct cachefiles_xattr *auxdata);
+extern int cachefiles_check_auxdata(struct cachefiles_object *object);
 extern int cachefiles_check_object_xattr(struct cachefiles_object *object,
                                          struct cachefiles_xattr *auxdata);
 extern int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index 2476e5162609..34c88b83e39f 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -157,6 +157,42 @@ int cachefiles_update_object_xattr(struct cachefiles_object *object,
 }
 
 /*
+ * check the consistency between the backing cache and the FS-Cache cookie
+ */
+int cachefiles_check_auxdata(struct cachefiles_object *object)
+{
+        struct cachefiles_xattr *auxbuf;
+        struct dentry *dentry = object->dentry;
+        unsigned int dlen;
+        int ret;
+
+        ASSERT(dentry);
+        ASSERT(dentry->d_inode);
+        ASSERT(object->fscache.cookie->def->check_aux);
+
+        auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
+        if (!auxbuf)
+                return -ENOMEM;
+
+        auxbuf->len = vfs_getxattr(dentry, cachefiles_xattr_cache,
+                                   &auxbuf->type, 512 + 1);
+        if (auxbuf->len < 1)
+                return -ESTALE;
+
+        if (auxbuf->type != object->fscache.cookie->def->type)
+                return -ESTALE;
+
+        dlen = auxbuf->len - 1;
+        ret = fscache_check_aux(&object->fscache, &auxbuf->data, dlen);
+
+        kfree(auxbuf);
+        if (ret != FSCACHE_CHECKAUX_OKAY)
+                return -ESTALE;
+
+        return 0;
+}
+
+/*
  * check the state xattr on a cache file
  * - return -ESTALE if the object should be deleted
  */