virtio-9p: Implement server side of setattr for 9P2000.L protocol.

SYNOPSIS

      size[4] Tsetattr tag[2] attr[n]

      size[4] Rsetattr tag[2]

   DESCRIPTION

      The setattr command changes some of the file status information.
      attr resembles the iattr structure used in Linux kernel. It
      specifies which status parameter is to be changed and to what
      value. It is laid out as follows:

         valid[4]
            specifies which status information is to be changed. Possible
            values are:
            ATTR_MODE       (1 << 0)
            ATTR_UID        (1 << 1)
            ATTR_GID        (1 << 2)
            ATTR_SIZE       (1 << 3)
            ATTR_ATIME      (1 << 4)
            ATTR_MTIME      (1 << 5)
            ATTR_CTIME      (1 << 5)
            ATTR_ATIME_SET  (1 << 7)
            ATTR_MTIME_SET  (1 << 8)

            The last two bits represent whether the time information
            is being sent by the client's user space. In the absense
            of these bits the server always uses server's time.

         mode[4]
            File permission bits

         uid[4]
            Owner id of file

         gid[4]
            Group id of the file

         size[8]
            File size

         atime_sec[8]
            Time of last file access, seconds

         atime_nsec[8]
            Time of last file access, nanoseconds

         mtime_sec[8]
            Time of last file modification, seconds

         mtime_nsec[8]
            Time of last file modification, nanoseconds

Explanation of the patches:
--------------------------

*) The kernel just copies relevent contents of iattr structure to p9_iattr_dotl
   structure and passes it down to the client. The only check it has is calling
   inode_change_ok()
*) The p9_iattr_dotl structure does not have ctime and ia_file parameters because
   I don't think these are needed in our case. The client user space can request
   updating just ctime by calling chown(fd, -1, -1). This is handled on server
   side without a need for putting ctime on the wire.
*) The server currently supports changing mode, time, ownership and size of the
   file.
*) 9P RFC says "Either all the changes in wstat request happen, or none of them
   does: if the request succeeds, all changes were made; if it fails, none were."
   I have not done anything to implement this specifically because I don't see
   a reason.

[jvrao@linux.vnet.ibm.com: Parts of code for handling chown(-1,-1)
Signed-off-by: NSripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: NVenkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

hw/virtio-9p-local.c

@@ -442,7 +442,10 @@ static int local_rename(FsContext *ctx, const char *oldpath,
 
 static int local_chown(FsContext *fs_ctx, const char *path, FsCred *credp)
 {
-    if (fs_ctx->fs_sm == SM_MAPPED) {
+    if ((credp->fc_uid == -1 && credp->fc_gid == -1) ||
+            (fs_ctx->fs_sm == SM_PASSTHROUGH)) {
+        return lchown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);
+    } else if (fs_ctx->fs_sm == SM_MAPPED) {
         return local_set_xattr(rpath(fs_ctx, path), credp);
     } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
         return lchown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);

hw/virtio-9p.c

@@ -665,6 +665,15 @@ static size_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
                         &statp->n_muid);
             break;
         }
+        case 'I': {
+            V9fsIattr *iattr = va_arg(ap, V9fsIattr *);
+            offset += pdu_unmarshal(pdu, offset, "ddddqqqqq",
+                        &iattr->valid, &iattr->mode,
+                        &iattr->uid, &iattr->gid, &iattr->size,
+                        &iattr->atime_sec, &iattr->atime_nsec,
+                        &iattr->mtime_sec, &iattr->mtime_nsec);
+            break;
+        }
         default:
             break;
         }
@@ -1240,6 +1249,151 @@ out:
     qemu_free(vs);
 }
 
+/* From Linux kernel code */
+#define ATTR_MODE    (1 << 0)
+#define ATTR_UID     (1 << 1)
+#define ATTR_GID     (1 << 2)
+#define ATTR_SIZE    (1 << 3)
+#define ATTR_ATIME   (1 << 4)
+#define ATTR_MTIME   (1 << 5)
+#define ATTR_CTIME   (1 << 6)
+#define ATTR_MASK    127
+#define ATTR_ATIME_SET  (1 << 7)
+#define ATTR_MTIME_SET  (1 << 8)
+
+static void v9fs_setattr_post_truncate(V9fsState *s, V9fsSetattrState *vs,
+                                                                  int err)
+{
+    if (err == -1) {
+        err = -errno;
+        goto out;
+    }
+    err = vs->offset;
+
+out:
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
+static void v9fs_setattr_post_chown(V9fsState *s, V9fsSetattrState *vs, int err)
+{
+    if (err == -1) {
+        err = -errno;
+        goto out;
+    }
+
+    if (vs->v9iattr.valid & (ATTR_SIZE)) {
+        err = v9fs_do_truncate(s, &vs->fidp->path, vs->v9iattr.size);
+    }
+    v9fs_setattr_post_truncate(s, vs, err);
+    return;
+
+out:
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
+static void v9fs_setattr_post_utimensat(V9fsState *s, V9fsSetattrState *vs,
+                                                                   int err)
+{
+    if (err == -1) {
+        err = -errno;
+        goto out;
+    }
+
+    /* If the only valid entry in iattr is ctime we can call
+     * chown(-1,-1) to update the ctime of the file
+     */
+    if ((vs->v9iattr.valid & (ATTR_UID | ATTR_GID)) ||
+            ((vs->v9iattr.valid & ATTR_CTIME)
+            && !((vs->v9iattr.valid & ATTR_MASK) & ~ATTR_CTIME))) {
+        if (!(vs->v9iattr.valid & ATTR_UID)) {
+            vs->v9iattr.uid = -1;
+        }
+        if (!(vs->v9iattr.valid & ATTR_GID)) {
+            vs->v9iattr.gid = -1;
+        }
+        err = v9fs_do_chown(s, &vs->fidp->path, vs->v9iattr.uid,
+                                                vs->v9iattr.gid);
+    }
+    v9fs_setattr_post_chown(s, vs, err);
+    return;
+
+out:
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
+static void v9fs_setattr_post_chmod(V9fsState *s, V9fsSetattrState *vs, int err)
+{
+    if (err == -1) {
+        err = -errno;
+        goto out;
+    }
+
+    if (vs->v9iattr.valid & (ATTR_ATIME | ATTR_MTIME)) {
+        struct timespec times[2];
+        if (vs->v9iattr.valid & ATTR_ATIME) {
+            if (vs->v9iattr.valid & ATTR_ATIME_SET) {
+                times[0].tv_sec = vs->v9iattr.atime_sec;
+                times[0].tv_nsec = vs->v9iattr.atime_nsec;
+            } else {
+                times[0].tv_nsec = UTIME_NOW;
+            }
+        } else {
+            times[0].tv_nsec = UTIME_OMIT;
+        }
+
+        if (vs->v9iattr.valid & ATTR_MTIME) {
+            if (vs->v9iattr.valid & ATTR_MTIME_SET) {
+                times[1].tv_sec = vs->v9iattr.mtime_sec;
+                times[1].tv_nsec = vs->v9iattr.mtime_nsec;
+            } else {
+                times[1].tv_nsec = UTIME_NOW;
+            }
+        } else {
+            times[1].tv_nsec = UTIME_OMIT;
+        }
+        err = v9fs_do_utimensat(s, &vs->fidp->path, times);
+    }
+    v9fs_setattr_post_utimensat(s, vs, err);
+    return;
+
+out:
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
+static void v9fs_setattr(V9fsState *s, V9fsPDU *pdu)
+{
+    int32_t fid;
+    V9fsSetattrState *vs;
+    int err = 0;
+
+    vs = qemu_malloc(sizeof(*vs));
+    vs->pdu = pdu;
+    vs->offset = 7;
+
+    pdu_unmarshal(pdu, vs->offset, "dI", &fid, &vs->v9iattr);
+
+    vs->fidp = lookup_fid(s, fid);
+    if (vs->fidp == NULL) {
+        err = -EINVAL;
+        goto out;
+    }
+
+    if (vs->v9iattr.valid & ATTR_MODE) {
+        err = v9fs_do_chmod(s, &vs->fidp->path, vs->v9iattr.mode);
+    }
+
+    v9fs_setattr_post_chmod(s, vs, err);
+    return;
+
+out:
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
 static void v9fs_walk_complete(V9fsState *s, V9fsWalkState *vs, int err)
 {
     complete_pdu(s, vs->pdu, err);
@@ -2514,6 +2668,7 @@ static pdu_handler_t *pdu_handlers[] = {
     [P9_TREADDIR] = v9fs_readdir,
     [P9_TSTATFS] = v9fs_statfs,
     [P9_TGETATTR] = v9fs_getattr,
+    [P9_TSETATTR] = v9fs_setattr,
     [P9_TVERSION] = v9fs_version,
     [P9_TATTACH] = v9fs_attach,
     [P9_TSTAT] = v9fs_stat,

hw/virtio-9p.h

@@ -17,6 +17,8 @@ enum {
     P9_RSTATFS,
     P9_TGETATTR = 24,
     P9_RGETATTR,
+    P9_TSETATTR = 26,
+    P9_RSETATTR,
     P9_TREADDIR = 40,
     P9_RREADDIR,
     P9_TVERSION = 100,
@@ -290,6 +292,27 @@ typedef struct V9fsWstatState
     V9fsString nname;
 } V9fsWstatState;
 
+typedef struct V9fsIattr
+{
+    int32_t valid;
+    int32_t mode;
+    int32_t uid;
+    int32_t gid;
+    int64_t size;
+    int64_t atime_sec;
+    int64_t atime_nsec;
+    int64_t mtime_sec;
+    int64_t mtime_nsec;
+} V9fsIattr;
+
+typedef struct V9fsSetattrState
+{
+    V9fsPDU *pdu;
+    size_t offset;
+    V9fsIattr v9iattr;
+    V9fsFidState *fidp;
+} V9fsSetattrState;
+
 struct virtio_9p_config
 {
     /* number of characters in tag */