[Qemu-devel] [PATCH 3/5] 9pfs: local: simplify file opening

[Greg Kurz]

All paths in the virtfs directory now start with "./" (except the virtfs
root itself which is exactly ".").

We hence don't need to skip leading '/' characters anymore, nor to handle
the empty path case. Also, since virtfs will only ever be supported on
linux+glibc hosts, we can use strchrnul() and come up with a much simplier
code to walk through the path elements. And we don't need to dup() the
passed directory fd.

Signed-off-by: Greg Kurz <gr...@kaod.org>
---
 hw/9pfs/9p-local.c |    5 -----
 hw/9pfs/9p-util.c  |   26 ++++++++++----------------
 2 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 92262f3c3e37..bb6e296df317 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -54,11 +54,6 @@ int local_open_nofollow(FsContext *fs_ctx, const char *path, 
int flags,
 {
     LocalData *data = fs_ctx->private;
 
-    /* All paths are relative to the path data->mountfd points to */
-    while (*path == '/') {
-        path++;
-    }
-
     return relative_openat_nofollow(data->mountfd, path, flags, mode);
 }
 
diff --git a/hw/9pfs/9p-util.c b/hw/9pfs/9p-util.c
index fdb4d5737635..e46399a9119d 100644
--- a/hw/9pfs/9p-util.c
+++ b/hw/9pfs/9p-util.c
@@ -17,14 +17,11 @@
 int relative_openat_nofollow(int dirfd, const char *path, int flags,
                              mode_t mode)
 {
-    int fd;
+    int fd = dirfd;
 
-    fd = dup(dirfd);
-    if (fd == -1) {
-        return -1;
-    }
+    assert(*path);
 
-    while (*path) {
+    while (*path && fd != -1) {
         const char *c;
         int next_fd;
         char *head;
@@ -33,25 +30,22 @@ int relative_openat_nofollow(int dirfd, const char *path, 
int flags,
         assert(path[0] != '/');
 
         head = g_strdup(path);
-        c = strchr(path, '/');
-        if (c) {
+        c = strchrnul(path, '/');
+        if (*c) {
+            /* Intermediate path element */
             head[c - path] = 0;
+            path = c + 1;
             next_fd = openat_dir(fd, head);
         } else {
+            /* Rightmost path element */
             next_fd = openat_file(fd, head, flags, mode);
+            path = c;
         }
         g_free(head);
-        if (next_fd == -1) {
+        if (dirfd != fd) {
             close_preserve_errno(fd);
-            return -1;
         }
-        close(fd);
         fd = next_fd;
-
-        if (!c) {
-            break;
-        }
-        path = c + 1;
     }
 
     return fd;