+ if (tvp == dvp) {
+ *is_subdir = TRUE;
+ break;
+ } else if (tvp == rootvnode) {
+ /* *is_subdir = FALSE */
+ break;
+ }
+
+ tmp = tvp->v_mount;
+ while ((tvp->v_flag & VROOT) && tmp && tmp->mnt_vnodecovered &&
+ tvp != dvp && tvp != rootvnode) {
+ tvp = tmp->mnt_vnodecovered;
+ tmp = tvp->v_mount;
+ }
+
+ /*
+ * If dvp is not at the top of a mount "stack" then
+ * vp is not a subdirectory of dvp either.
+ */
+ if (tvp == dvp || tvp == rootvnode) {
+ /* *is_subdir = FALSE */
+ break;
+ }
+
+ if (!tmp) {
+ defer = TRUE;
+ *next_vp = NULLVP;
+ break;
+ }
+
+ if ((tvp->v_flag & VISHARDLINK) || !(tvp->v_parent)) {
+ defer = TRUE;
+ *next_vp = tvp;
+ break;
+ }
+
+ tvp = tvp->v_parent;
+ }
+
+ return (defer);
+}
+
+/* maximum times retry from potentially transient errors in vnode_issubdir */
+#define MAX_ERROR_RETRY 3
+
+/*
+ * This function checks if a given directory (vp) is a subdirectory of dvp.
+ * It walks backwards from vp and if it hits dvp in its parent chain,
+ * it is a subdirectory. If it encounters the root directory, it is not
+ * a subdirectory.
+ *
+ * This function returns an error if it is unsuccessful and 0 on success.
+ *
+ * On entry (and exit) vp has an iocount and if this function has to take
+ * any iocounts on other vnodes in the parent chain traversal, it releases them.
+ */
+int
+vnode_issubdir(vnode_t vp, vnode_t dvp, int *is_subdir, vfs_context_t ctx)
+{
+ vnode_t start_vp, tvp;
+ vnode_t vp_with_iocount;
+ int error = 0;
+ char dotdotbuf[] = "..";
+ int error_retry_count = 0; /* retry count for potentially transient
+ errors */
+
+ *is_subdir = FALSE;
+ tvp = start_vp = vp;
+ /*
+ * Anytime we acquire an iocount in this function, we save the vnode
+ * in this variable and release it before exiting.
+ */
+ vp_with_iocount = NULLVP;
+
+ while (1) {
+ boolean_t defer;
+ vnode_t pvp;
+ uint32_t vid;
+ struct componentname cn;
+ boolean_t is_subdir_locked = FALSE;
+
+ if (tvp == dvp) {
+ *is_subdir = TRUE;
+ break;
+ } else if (tvp == rootvnode) {
+ /* *is_subdir = FALSE */
+ break;
+ }
+
+ NAME_CACHE_LOCK_SHARED();
+
+ defer = cache_check_vnode_issubdir(tvp, dvp, &is_subdir_locked,
+ &tvp);
+
+ if (defer && tvp)
+ vid = vnode_vid(tvp);
+
+ NAME_CACHE_UNLOCK();
+
+ if (!defer) {
+ *is_subdir = is_subdir_locked;
+ break;
+ }
+
+ if (!tvp) {
+ if (error_retry_count++ < MAX_ERROR_RETRY) {
+ tvp = vp;
+ continue;
+ }
+ error = ENOENT;
+ break;
+ }
+
+ if (tvp != start_vp) {
+ if (vp_with_iocount) {
+ vnode_put(vp_with_iocount);
+ vp_with_iocount = NULLVP;
+ }
+
+ error = vnode_getwithvid(tvp, vid);
+ if (error) {
+ if (error_retry_count++ < MAX_ERROR_RETRY) {
+ tvp = vp;
+ error = 0;
+ continue;
+ }
+ break;
+ }
+
+ vp_with_iocount = tvp;
+ }
+
+ bzero(&cn, sizeof(cn));
+ cn.cn_nameiop = LOOKUP;
+ cn.cn_flags = ISLASTCN | ISDOTDOT;
+ cn.cn_context = ctx;
+ cn.cn_pnbuf = &dotdotbuf[0];
+ cn.cn_pnlen = sizeof(dotdotbuf);
+ cn.cn_nameptr = cn.cn_pnbuf;
+ cn.cn_namelen = 2;
+
+ pvp = NULLVP;
+ if ((error = VNOP_LOOKUP(tvp, &pvp, &cn, ctx)))
+ break;
+
+ if (!(tvp->v_flag & VISHARDLINK) && tvp->v_parent != pvp) {
+ (void)vnode_update_identity(tvp, pvp, NULL, 0, 0,
+ VNODE_UPDATE_PARENT);
+ }
+
+ if (vp_with_iocount)
+ vnode_put(vp_with_iocount);
+
+ vp_with_iocount = tvp = pvp;
+ }
+
+ if (vp_with_iocount)
+ vnode_put(vp_with_iocount);
+
+ return (error);
+}
+
+/*
+ * This function builds the path in "buff" from the supplied vnode.
+ * The length of the buffer *INCLUDING* the trailing zero byte is
+ * returned in outlen. NOTE: the length includes the trailing zero
+ * byte and thus the length is one greater than what strlen would
+ * return. This is important and lots of code elsewhere in the kernel
+ * assumes this behavior.
+ *
+ * This function can call vnop in file system if the parent vnode
+ * does not exist or when called for hardlinks via volfs path.
+ * If BUILDPATH_NO_FS_ENTER is set in flags, it only uses values present
+ * in the name cache and does not enter the file system.
+ *
+ * If BUILDPATH_CHECK_MOVED is set in flags, we return EAGAIN when
+ * we encounter ENOENT during path reconstruction. ENOENT means that
+ * one of the parents moved while we were building the path. The
+ * caller can special handle this case by calling build_path again.
+ *
+ * If BUILDPATH_VOLUME_RELATIVE is set in flags, we return path
+ * that is relative to the nearest mount point, i.e. do not
+ * cross over mount points during building the path.
+ *
+ * passed in vp must have a valid io_count reference
+ *
+ * If parent vnode is non-NULL it also must have an io count. This
+ * allows build_path_with_parent to be safely called for operations
+ * unlink, rmdir and rename that already have io counts on the target
+ * and the directory. In this way build_path_with_parent does not have
+ * to try and obtain an additional io count on the parent. Taking an
+ * io count ont the parent can lead to dead lock if a forced unmount
+ * occures at the right moment. For a fuller explaination on how this
+ * can occur see the comment for vn_getpath_with_parent.
+ *
+ */
projects / apple / xnu.git / blobdiff