Print a warning when opening a file O_DIRECT on tmpfs fails with EINVAL.
This saves users a lot of time trying to figure out the EINVAL error.
Reported-by: Deepak C Shetty <deepa...@linux.vnet.ibm.com>
Suggested-by: Eric Blake <ebl...@redhat.com>
Suggested-by: Daniel P. Berrange <berra...@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
util/osdep.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 55 insertions(+), 7 deletions(-)
diff --git a/util/osdep.c b/util/osdep.c
index 685c8ae..cbee2b7 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -148,6 +148,23 @@ static int qemu_parse_fdset(const char *param)
#endif
/*
+ * Open a file with O_CLOEXEC semantics
+ */
+static int open_cloexec(const char *name, int flags, int mode)
+{
+ int ret;
+#ifdef O_CLOEXEC
+ ret = open(name, flags | O_CLOEXEC, mode);
+#else
+ ret = open(name, flags, mode);
+ if (ret >= 0) {
+ qemu_set_cloexec(ret);
+ }
+#endif
+ return ret;
+}
+
+/*
* Opens a file with FD_CLOEXEC set
*/
int qemu_open(const char *name, int flags, ...)
@@ -198,14 +215,45 @@ int qemu_open(const char *name, int flags, ...)
va_end(ap);
}
-#ifdef O_CLOEXEC
- ret = open(name, flags | O_CLOEXEC, mode);
-#else
- ret = open(name, flags, mode);
- if (ret >= 0) {
- qemu_set_cloexec(ret);
+ /* Some file systems do not support O_DIRECT and fail with EINVAL. Confirm
+ * the problem by trying again without O_DIRECT and printing a warning.
+ *
+ * Sounds easy enough but we need to be careful with O_CREAT since this
+ * function should not create a file when an error is returned.
+ */
+ if (flags & (O_CREAT | O_DIRECT) == O_CREAT | O_DIRECT) {
+ ret = open_cloexec(name, flags | O_EXCL, mode);
+
+ if (ret >= 0) {
+ return ret;
+ }
+
+ if (errno == EINVAL) {
+ error_report("file system may not support O_DIRECT");
+ errno = EINVAL; /* in case it was clobbered */
+ return ret;
+ } else if (errno == EEXIST && (flags & O_EXCL) == 0) {
+ /* We know the file existed, drop O_CREAT so the following open
+ * attempts do not create a file if O_DIRECT produces EINVAL. Note
+ * there is a race condition here if the file is deleted while we
+ * perform our open calls.
+ */
+ flags &= O_CREAT;
+ } else {
+ return ret;
+ }
+ }
+
+ ret = open_cloexec(name, flags, mode);
+
+ if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
+ int fd = open_cloexec(name, flags & ~O_DIRECT, mode);
+ if (fd >= 0) {
+ close(fd);
+ error_report("file system does not support O_DIRECT");
+ }
+ errno = EINVAL; /* in case it was clobbered */
}
-#endif
return ret;
}
--
1.8.3.1
