9pfs: fix readdir() for 9p2000.u

If the client is using 9p2000.u, the following occurs:

$ cd ${virtfs_shared_dir}
$ mkdir -p a/b/c
$ ls a/b
ls: cannot access 'a/b/a': No such file or directory
ls: cannot access 'a/b/b': No such file or directory
a  b  c

instead of the expected:

$ ls a/b
c

This is a regression introduced by commit f57f587;
local_name_to_path() now resolves ".." and "." in paths,
and v9fs_do_readdir_with_stat()->stat_to_v9stat() then
copies the basename of the resulting path to the response.
With the example above, this means that "." and ".." are
turned into "b" and "a" respectively...

stat_to_v9stat() currently assumes it is passed a full
canonicalized path and uses it to do two different things:
1) to pass it to v9fs_co_readlink() in case the file is a symbolic
   link
2) to set the name field of the V9fsStat structure to the basename
   part of the given path

It only has two users: v9fs_stat() and v9fs_do_readdir_with_stat().

v9fs_stat() really needs 1) and 2) to be performed since it starts
with the full canonicalized path stored in the fid. It is different
for v9fs_do_readdir_with_stat() though because the name we want to
put into the V9fsStat structure is the d_name field of the dirent
actually (ie, we want to keep the "." and ".." special names). So,
we only need 1) in this case.

This patch hence adds a basename argument to stat_to_v9stat(), to
be used to set the name field of the V9fsStat structure, and moves
the basename logic to v9fs_stat().

Signed-off-by: Jan Dakinevich <jan.dakinevich@gmail.com>
(groug, renamed old name argument to path and updated changelog)
Signed-off-by: Greg Kurz <groug@kaod.org>

(cherry picked from commit 6069537)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/9pfs/9p.c

@@ -803,12 +803,12 @@ static uint32_t stat_to_v9mode(const struct stat *stbuf)
     return mode;
 }
 
-static int coroutine_fn stat_to_v9stat(V9fsPDU *pdu, V9fsPath *name,
+static int coroutine_fn stat_to_v9stat(V9fsPDU *pdu, V9fsPath *path,
+                                       const char *basename,
                                        const struct stat *stbuf,
                                        V9fsStat *v9stat)
 {
     int err;
-    const char *str;
 
     memset(v9stat, 0, sizeof(*v9stat));
 
@@ -829,7 +829,7 @@ static int coroutine_fn stat_to_v9stat(V9fsPDU *pdu, V9fsPath *name,
     v9fs_string_free(&v9stat->extension);
 
     if (v9stat->mode & P9_STAT_MODE_SYMLINK) {
-        err = v9fs_co_readlink(pdu, name, &v9stat->extension);
+        err = v9fs_co_readlink(pdu, path, &v9stat->extension);
         if (err < 0) {
             return err;
         }
@@ -842,14 +842,7 @@ static int coroutine_fn stat_to_v9stat(V9fsPDU *pdu, V9fsPath *name,
                 "HARDLINKCOUNT", (unsigned long)stbuf->st_nlink);
     }
 
-    str = strrchr(name->data, '/');
-    if (str) {
-        str += 1;
-    } else {
-        str = name->data;
-    }
-
-    v9fs_string_sprintf(&v9stat->name, "%s", str);
+    v9fs_string_sprintf(&v9stat->name, "%s", basename);
 
     v9stat->size = 61 +
         v9fs_string_size(&v9stat->name) +
@@ -1058,6 +1051,7 @@ static void coroutine_fn v9fs_stat(void *opaque)
     struct stat stbuf;
     V9fsFidState *fidp;
     V9fsPDU *pdu = opaque;
+    char *basename;
 
     err = pdu_unmarshal(pdu, offset, "d", &fid);
     if (err < 0) {
@@ -1074,7 +1068,9 @@ static void coroutine_fn v9fs_stat(void *opaque)
     if (err < 0) {
         goto out;
     }
-    err = stat_to_v9stat(pdu, &fidp->path, &stbuf, &v9stat);
+    basename = g_path_get_basename(fidp->path.data);
+    err = stat_to_v9stat(pdu, &fidp->path, basename, &stbuf, &v9stat);
+    g_free(basename);
     if (err < 0) {
         goto out;
     }
@@ -1750,7 +1746,7 @@ static int coroutine_fn v9fs_do_readdir_with_stat(V9fsPDU *pdu,
         if (err < 0) {
             break;
         }
-        err = stat_to_v9stat(pdu, &path, &stbuf, &v9stat);
+        err = stat_to_v9stat(pdu, &path, dent->d_name, &stbuf, &v9stat);
         if (err < 0) {
             break;
         }