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>
diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index 93a0815..2c99488 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -174,7 +174,10 @@
_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);