Print a warning when opening a file O_DIRECT on tmpfs fails. This saves
users a lot of time trying to figure out the EINVAL error.
Daniel P. Berrange <berra...@redhat.com> suggested opening the file
without O_DIRECT as a portable way to check whether the file system
supports O_DIRECT. That gets messy when flags contains O_CREAT since
we'd create a file but return an error - or a race condition if we try
to unlink the file. It's simpler to check the file system type.
Reported-by: Deepak C Shetty <deepa...@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
util/osdep.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/util/osdep.c b/util/osdep.c
index 685c8ae..446a1dc 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -30,6 +30,11 @@
#include <unistd.h>
#include <fcntl.h>
+#ifdef __linux__
+#include <sys/vfs.h>
+#include <linux/magic.h>
+#endif
+
/* Needed early for CONFIG_BSD etc. */
#include "config-host.h"
@@ -207,6 +212,20 @@ int qemu_open(const char *name, int flags, ...)
}
#endif
+#ifdef __linux__
+ /* It is not possible to open files O_DIRECT on tmpfs. Provide a hint that
+ * this may be the case (of course it could change in future kernel
+ * versions).
+ */
+ if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
+ struct statfs st;
+ if (statfs(name, &st) == 0 && st.f_type == TMPFS_MAGIC) {
+ error_report("tmpfs file systems may not support O_DIRECT");
+ }
+ errno = EINVAL; /* in case it was clobbered */
+ }
+#endif /* __linux__ */
+
return ret;
}
--
1.8.3.1
