fuse: disable the combination of passthrough and writeback cache
Current design and handling of passthrough is without fuse
caching and with that FUSE_WRITEBACK_CACHE is conflicting.
Fixes: 7dc4e97a4f9a ("fuse: introduce FUSE_PASSTHROUGH capability")
Cc: stable@kernel.org # v6.9
Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Acked-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index d8ab4e9..bebd890 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1332,11 +1332,16 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
* on a stacked fs (e.g. overlayfs) themselves and with
* max_stack_depth == 1, FUSE fs can be stacked as the
* underlying fs of a stacked fs (e.g. overlayfs).
+ *
+ * Also don't allow the combination of FUSE_PASSTHROUGH
+ * and FUSE_WRITEBACK_CACHE, current design doesn't handle
+ * them together.
*/
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH) &&
(flags & FUSE_PASSTHROUGH) &&
arg->max_stack_depth > 0 &&
- arg->max_stack_depth <= FILESYSTEM_MAX_STACK_DEPTH) {
+ arg->max_stack_depth <= FILESYSTEM_MAX_STACK_DEPTH &&
+ !(flags & FUSE_WRITEBACK_CACHE)) {
fc->passthrough = 1;
fc->max_stack_depth = arg->max_stack_depth;
fm->sb->s_stack_depth = arg->max_stack_depth;
