qcow2: Add lock for lookup cache and decompression

Race conditions can occur if reads are submitted from different
cgroups, as each cgroup has its own workqueue. Linearize the
according parts of the code using a mutex, as this will in the
worst case lead to performance on par with pre-5.15 versions
of xloop, which used one workqueue for all cgroups.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/kernel/xloop_file_fmt_qcow_main.h b/src/kernel/xloop_file_fmt_qcow_main.h
index aff5e13..32e14f9 100644
--- a/src/kernel/xloop_file_fmt_qcow_main.h
+++ b/src/kernel/xloop_file_fmt_qcow_main.h
@@ -291,6 +291,8 @@ struct xloop_file_fmt_qcow_data {
 	u64           compatible_features;
 	u64           autoclear_features;
 
+	struct mutex  global_mutex;
+
 	/* ZLIB specific data */
 	z_streamp     zlib_dstrm;