From 85a876e0d28eac4c71350baede38ca755fdf6df0 Mon Sep 17 00:00:00 2001
From: Jinhua Cao <caojinhua1@huawei.com>
Date: Thu, 24 Mar 2022 17:12:49 +0800
Subject: [PATCH] qemu-img create: 'cache' paramter only use for reg file image

The paramter 'cache' is invalid for host device(/dev/xxx). If
'qemu-img create' operator performed on host device, the host
device not support 'cache' would result 'qemu-img create' execute
failed.

Signed-off-by: Jinhua Cao <caojinhua1@huawei.com>
---
 qemu-img.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/qemu-img.c b/qemu-img.c
index 9409558772..059bf42fc1 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -496,6 +496,22 @@ static int64_t cvtnum(const char *name, const char *value)
     return cvtnum_full(name, value, 0, INT64_MAX);
 }
 
+static bool is_reg_file(const char *filename)
+{
+    struct stat st;
+
+    /* file not exist, file will be create later, so it's a reg file */
+    if (access(filename, F_OK) == -1) {
+        return true;
+    }
+
+    /* file exist, check file type */
+    if (stat(filename, &st) >= 0 && S_ISREG(st.st_mode)) {
+        return true;
+    }
+    return false;
+}
+
 static int img_create(int argc, char **argv)
 {
     int c;
@@ -586,12 +602,14 @@ static int img_create(int argc, char **argv)
         error_exit("Unexpected argument: %s", argv[optind]);
     }
 
-    if (!options) {
-        options = g_strdup_printf(BLOCK_OPT_CACHE"=%s", cache);
-    } else {
-        char *old_options = options;
-        options = g_strdup_printf("%s,"BLOCK_OPT_CACHE"=%s", options, cache);
-        g_free(old_options);
+    if (is_reg_file(filename)) {
+        if (!options) {
+            options = g_strdup_printf(BLOCK_OPT_CACHE"=%s", cache);
+        } else {
+            char *old_options = options;
+            options = g_strdup_printf("%s,"BLOCK_OPT_CACHE"=%s", options, cache);
+            g_free(old_options);
+        }
     }
 
     bdrv_img_create(filename, fmt, base_filename, base_fmt,
-- 
2.27.0