9pfs: local: simplify file opening

The logic to open a path currently sits between local_open_nofollow() and
the relative_openat_nofollow() helper, which has no other user.

For the sake of clarity, this patch moves all the code of the helper into
its unique caller. While here we also:
- drop the code to skip leading "/" because the backend isn't supposed to
  pass anything but relative paths without consecutive slashes. The assert()
  is kept because we really don't want a buggy backend to pass an absolute
  path to openat().
- use strchrnul() to get a simpler code. This is ok since virtfs is for
  linux+glibc hosts only.
- don't dup() the initial directory and add an assert() to ensure we don't
  return the global mountfd to the caller. BTW, this would mean that the
  caller passed an empty path, which isn't supposed to happen either.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
[groug: fixed typos in changelog]

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 68e92652ed7339ab613a6f4cdbb36e7a069f5034..ddc5038cff398d0277f13924ba18d802ea572ff5 100644 (file)
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -53,13 +53,37 @@ int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags,
                         mode_t mode)
 {
     LocalData *data = fs_ctx->private;
-
-    /* All paths are relative to the path data->mountfd points to */
-    while (*path == '/') {
-        path++;
+    int fd = data->mountfd;
+
+    while (*path && fd != -1) {
+        const char *c;
+        int next_fd;
+        char *head;
+
+        /* Only relative paths without consecutive slashes */
+        assert(*path != '/');
+
+        head = g_strdup(path);
+        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 (fd != data->mountfd) {
+            close_preserve_errno(fd);
+        }
+        fd = next_fd;
     }
 
-    return relative_openat_nofollow(data->mountfd, path, flags, mode);
+    assert(fd != data->mountfd);
+    return fd;
 }
 
 int local_opendir_nofollow(FsContext *fs_ctx, const char *path)

diff --git a/hw/9pfs/9p-util.c b/hw/9pfs/9p-util.c
index fdb4d5737635ee1cb43f8ed4c233a3527077312c..f709c27a1fbdfa19dd5d8b1202e34d203c33c04b 100644 (file)
--- a/hw/9pfs/9p-util.c
+++ b/hw/9pfs/9p-util.c
@@ -14,49 +14,6 @@
 #include "qemu/xattr.h"
 #include "9p-util.h"
 
-int relative_openat_nofollow(int dirfd, const char *path, int flags,
-                             mode_t mode)
-{
-    int fd;
-
-    fd = dup(dirfd);
-    if (fd == -1) {
-        return -1;
-    }
-
-    while (*path) {
-        const char *c;
-        int next_fd;
-        char *head;
-
-        /* Only relative paths without consecutive slashes */
-        assert(path[0] != '/');
-
-        head = g_strdup(path);
-        c = strchr(path, '/');
-        if (c) {
-            head[c - path] = 0;
-            next_fd = openat_dir(fd, head);
-        } else {
-            next_fd = openat_file(fd, head, flags, mode);
-        }
-        g_free(head);
-        if (next_fd == -1) {
-            close_preserve_errno(fd);
-            return -1;
-        }
-        close(fd);
-        fd = next_fd;
-
-        if (!c) {
-            break;
-        }
-        path = c + 1;
-    }
-
-    return fd;
-}
-
 ssize_t fgetxattrat_nofollow(int dirfd, const char *filename, const char *name,
                              void *value, size_t size)
 {

diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
index 517027c5203250950dd9a7fdeb3f1e0720d97a0d..91299a24b8af755864f989b9213bf3087b5a652c 100644 (file)
--- a/hw/9pfs/9p-util.h
+++ b/hw/9pfs/9p-util.h
@@ -50,8 +50,6 @@ static inline int openat_file(int dirfd, const char *name, int flags,
     return fd;
 }
 
-int relative_openat_nofollow(int dirfd, const char *path, int flags,
-                             mode_t mode);
 ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
                              void *value, size_t size);
 int fsetxattrat_nofollow(int dirfd, const char *path, const char *name,