hw/9pfs: Add new virtfs option writeout=immediate skip host page cache

writeout=immediate implies the after pwritev we do a sync_file_range.

Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index dbf7778..b3c27f6 100644
--- a/vl.c
+++ b/vl.c
@@ -2785,6 +2785,7 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_virtfs: {
                 QemuOpts *fsdev;
                 QemuOpts *device;
+                const char *writeout;
 
                 olist = qemu_find_opts("virtfs");
                 if (!olist) {
@@ -2814,6 +2815,17 @@ int main(int argc, char **argv, char **envp)
                             qemu_opt_get(opts, "mount_tag"));
                     exit(1);
                 }
+
+                writeout = qemu_opt_get(opts, "writeout");
+                if (writeout) {
+#ifdef CONFIG_SYNC_FILE_RANGE
+                    qemu_opt_set(fsdev, "writeout", writeout);
+#else
+                    fprintf(stderr, "writeout=immediate not supported on "
+                            "this platform\n");
+                    exit(1);
+#endif
+                }
                 qemu_opt_set(fsdev, "fstype", qemu_opt_get(opts, "fstype"));
                 qemu_opt_set(fsdev, "path", qemu_opt_get(opts, "path"));
                 qemu_opt_set(fsdev, "security_model",