[V4] virtio-9p: readdir implementation for 9p2000.L

This patch implements the server part of readdir() implementation for
9p2000.L

    SYNOPSIS

    size[4] Treaddir tag[2] fid[4] offset[8] count[4]
    size[4] Rreaddir tag[2] count[4] data[count]

    DESCRIPTION

    The readdir request asks the server to read the directory specified by 'fid'
    at an offset specified by 'offset' and return as many dirent structures as
    possible that fit into count bytes. Each dirent structure is laid out as
    follows.

            qid.type[1]
              the type of the file (directory, etc.), represented as a bit
              vector corresponding to the high 8 bits of the file's mode
              word.

            qid.vers[4]
              version number for given path

            qid.path[8]
              the file server's unique identification for the file

            offset[8]
              offset into the next dirent.

            type[1]
              type of this directory entry.

            name[256]
              name of this directory entry.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Reviewed-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

hw/virtio-9p-debug.c

@@ -330,6 +330,19 @@ void pprint_pdu(V9fsPDU *pdu)
     BUG_ON(!llogfile);
 
     switch (pdu->id) {
+    case P9_TREADDIR:
+        fprintf(llogfile, "TREADDIR: (");
+        pprint_int32(pdu, 0, &offset, "fid");
+        pprint_int64(pdu, 0, &offset, ", initial offset");
+        pprint_int32(pdu, 0, &offset, ", max count");
+        break;
+    case P9_RREADDIR:
+        fprintf(llogfile, "RREADDIR: (");
+        pprint_int32(pdu, 1, &offset, "count");
+#ifdef DEBUG_DATA
+        pprint_data(pdu, 1, &offset, ", data");
+#endif
+        break;
     case P9_TVERSION:
         fprintf(llogfile, "TVERSION: (");
         pprint_int32(pdu, 0, &offset, "msize");

hw/virtio-9p.c

@@ -1577,6 +1577,127 @@ out:
     qemu_free(vs);
 }
 
+typedef struct V9fsReadDirState {
+    V9fsPDU *pdu;
+    V9fsFidState *fidp;
+    V9fsQID qid;
+    off_t saved_dir_pos;
+    struct dirent *dent;
+    int32_t count;
+    int32_t max_count;
+    size_t offset;
+    int64_t initial_offset;
+    V9fsString name;
+} V9fsReadDirState;
+
+static void v9fs_readdir_post_seekdir(V9fsState *s, V9fsReadDirState *vs)
+{
+    vs->offset += pdu_marshal(vs->pdu, vs->offset, "d", vs->count);
+    vs->offset += vs->count;
+    complete_pdu(s, vs->pdu, vs->offset);
+    qemu_free(vs);
+    return;
+}
+
+/* Size of each dirent on the wire: size of qid (13) + size of offset (8)
+ * size of type (1) + size of name.size (2) + strlen(name.data)
+ */
+#define V9_READDIR_DATA_SZ (24 + strlen(vs->name.data))
+
+static void v9fs_readdir_post_readdir(V9fsState *s, V9fsReadDirState *vs)
+{
+    int len;
+    size_t size;
+
+    if (vs->dent) {
+        v9fs_string_init(&vs->name);
+        v9fs_string_sprintf(&vs->name, "%s", vs->dent->d_name);
+
+        if ((vs->count + V9_READDIR_DATA_SZ) > vs->max_count) {
+            /* Ran out of buffer. Set dir back to old position and return */
+            v9fs_do_seekdir(s, vs->fidp->dir, vs->saved_dir_pos);
+            v9fs_readdir_post_seekdir(s, vs);
+            return;
+        }
+
+        /* Fill up just the path field of qid because the client uses
+         * only that. To fill the entire qid structure we will have
+         * to stat each dirent found, which is expensive
+         */
+        size = MIN(sizeof(vs->dent->d_ino), sizeof(vs->qid.path));
+        memcpy(&vs->qid.path, &vs->dent->d_ino, size);
+        /* Fill the other fields with dummy values */
+        vs->qid.type = 0;
+        vs->qid.version = 0;
+
+        len = pdu_marshal(vs->pdu, vs->offset+4+vs->count, "Qqbs",
+                              &vs->qid, vs->dent->d_off,
+                              vs->dent->d_type, &vs->name);
+        vs->count += len;
+        v9fs_string_free(&vs->name);
+        vs->saved_dir_pos = vs->dent->d_off;
+        vs->dent = v9fs_do_readdir(s, vs->fidp->dir);
+        v9fs_readdir_post_readdir(s, vs);
+        return;
+    }
+
+    vs->offset += pdu_marshal(vs->pdu, vs->offset, "d", vs->count);
+    vs->offset += vs->count;
+    complete_pdu(s, vs->pdu, vs->offset);
+    qemu_free(vs);
+    return;
+}
+
+static void v9fs_readdir_post_telldir(V9fsState *s, V9fsReadDirState *vs)
+{
+    vs->dent = v9fs_do_readdir(s, vs->fidp->dir);
+    v9fs_readdir_post_readdir(s, vs);
+    return;
+}
+
+static void v9fs_readdir_post_setdir(V9fsState *s, V9fsReadDirState *vs)
+{
+    vs->saved_dir_pos = v9fs_do_telldir(s, vs->fidp->dir);
+    v9fs_readdir_post_telldir(s, vs);
+    return;
+}
+
+static void v9fs_readdir(V9fsState *s, V9fsPDU *pdu)
+{
+    int32_t fid;
+    V9fsReadDirState *vs;
+    ssize_t err = 0;
+    size_t offset = 7;
+
+    vs = qemu_malloc(sizeof(*vs));
+    vs->pdu = pdu;
+    vs->offset = 7;
+    vs->count = 0;
+
+    pdu_unmarshal(vs->pdu, offset, "dqd", &fid, &vs->initial_offset,
+                                                        &vs->max_count);
+
+    vs->fidp = lookup_fid(s, fid);
+    if (vs->fidp == NULL || !(vs->fidp->dir)) {
+        err = -EINVAL;
+        goto out;
+    }
+
+    if (vs->initial_offset == 0) {
+        v9fs_do_rewinddir(s, vs->fidp->dir);
+    } else {
+        v9fs_do_seekdir(s, vs->fidp->dir, vs->initial_offset);
+    }
+
+    v9fs_readdir_post_setdir(s, vs);
+    return;
+
+out:
+    complete_pdu(s, pdu, err);
+    qemu_free(vs);
+    return;
+}
+
 static void v9fs_write_post_writev(V9fsState *s, V9fsWriteState *vs,
                                    ssize_t err)
 {
@@ -2210,6 +2331,7 @@ out:
 typedef void (pdu_handler_t)(V9fsState *s, V9fsPDU *pdu);
 
 static pdu_handler_t *pdu_handlers[] = {
+    [P9_TREADDIR] = v9fs_readdir,
     [P9_TSTATFS] = v9fs_statfs,
     [P9_TVERSION] = v9fs_version,
     [P9_TATTACH] = v9fs_attach,

hw/virtio-9p.h

@@ -15,6 +15,8 @@
 enum {
     P9_TSTATFS = 8,
     P9_RSTATFS,
+    P9_TREADDIR = 40,
+    P9_RREADDIR,
     P9_TVERSION = 100,
     P9_RVERSION,
     P9_TAUTH = 102,