[Qemu-devel] [PATCH 2/4] qcow2: Allow 'cache-clean-interval' in Linux only

[Alberto Garcia]

The cache-clean-interval option of qcow2 only works on Linux. However
we allow setting it in other systems regardless of whether it works or
not.

In those systems this option is not simply a no-op: it actually
invalidates perfectly valid cache tables for no good reason without
freeing their memory.

This patch forbids using that option in non-Linux systems.

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/qcow2.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 7cfcd84..ed9e0f3 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -668,6 +668,14 @@ static int qcow2_update_options_prepare(BlockDriverState 
*bs,
     r->cache_clean_interval =
         qemu_opt_get_number(opts, QCOW2_OPT_CACHE_CLEAN_INTERVAL,
                             s->cache_clean_interval);
+#ifndef CONFIG_LINUX
+    if (r->cache_clean_interval != 0) {
+        error_setg(errp, QCOW2_OPT_CACHE_CLEAN_INTERVAL
+                   " not supported on this host");
+        ret = -EINVAL;
+        goto fail;
+    }
+#endif
     if (r->cache_clean_interval > UINT_MAX) {
         error_setg(errp, "Cache clean interval too big");
         ret = -EINVAL;
-- 
2.10.2