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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: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2012-12-20 21:52:36 +00:00
parent a02de96085
commit 9dc8d9bfe4
2 changed files with 53 additions and 1 deletions
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49
fs/cachefiles/interface.c
View File

@ -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,

5
fs/cachefiles/rdwr.c
View File

@ -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);