posix: placeholders for GFID to path conversion

what?
=====
    The following is an attempt to generate the paths of a file when
    only its gfid is known.

    To find the path of a directory, the symlink handle to the
    directory maintained in  the ".glusterfs" backend directory is
    read. The symlink handle is generated using the gfid of the
    directory. It (handle) contains the directory's name and parent
    gfid, which are used to recursively construct the absolute path as
    seen by the user from the mount point.

    A similar approach cannot be used for a regular file or a symbolic
    link since its hardlink handle, generated using its gfid, doesn't
    contain its parent gfid and basename. So xattrs are set to store
    the parent gfids and the number of hardlinks to a file or a
    symlink having the same parent gfid.  When an user/application
    requests for the paths of a regular file or a symlink with
    multiple hardlinks, using the parent gfids stored in the xattrs,
    the paths of the parent directories are generated as mentioned
    earlier. The base names of the hardlinks (with the same parent
    gfid) are determined by matching the actual backend inode numbers
    of each entry in the parent directory with that of the hardlink
    handle.

    Xattr is set on a regular file, link, and symbolic link as
    follows, Xattr name : trusted.pgfid.<pargfidstr> Xattr value :
    <number of hardlinks to a regular file/symlink with the same
    parentgfid>

    If a regular file, hard link, symbolic link is created then an
    xattr in the above format is set in the backend.

how to use?
===========
    This functionality can be used through getxattr interface. Two
    keys - glusterfs.ancestry.dentry and glusterfs.ancestry.path - enable
    usage of this functionality. A successful getxattr will have the
    result stored under same keys. Values will be,

    glusterfs.ancestry.dentry:
    --------------------------
    A linked list of gf-dirent structures for all possible paths from
    root to this gfid. If there are multiple paths, the linked-list
    will be a series of paths one after another. Each path will be a
    series of dentries representing all components of the path. This
    key is primarily for internal usage within glusterfs.

    glusterfs.ancestry.path:
    ------------------------
    A string containing all possible paths from root to this gfid.
    Multiple hardlinks of a file or a symlink are displayed as a colon
    seperated list (this could interfere with path components
    containing ':').

    e.g. If there is a file "file1" in root directory with two hardlinks,
         "/dir2/link2tofile1" and "/dir1/link1tofile1", then

         [root@alpha gfsmntpt]# getfattr -n glusterfs.ancestry.path -e text
          file1
          glusterfs.ancestry.path="/file1:/dir2/link2tofile1:/dir1/link1tofile1"

    Thanks Amar, Avati and Venky for the inputs.

Original Author: Ramana Raja <rraja@redhat.com>
BUG: 990028
Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
Change-Id: I0eaa9101e333e0c1f66ccefd9e95944dd4a27497
Reviewed-on: http://review.gluster.org/5951
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 158 insertions, 4 deletions

diff --git a/xlators/storage/posix/src/posix-handle.c b/xlators/storage/posix/src/posix-handle.c
index 219a582c9..1d8e98631 100644
--- a/xlators/storage/posix/src/posix-handle.c
+++ b/xlators/storage/posix/src/posix-handle.c
@@ -26,13 +26,167 @@
 #include "xlator.h"
 #include "syscall.h"
 
+inode_t *
+posix_resolve (xlator_t *this, inode_table_t *itable, inode_t *parent,
+               char *bname, struct iatt *iabuf)
+{
+        inode_t     *inode = NULL, *linked_inode = NULL;
+        int          ret   = -1;
+
+        ret = posix_istat (this, parent->gfid, bname, iabuf);
+        if (ret < 0)
+                goto out;
+
+        inode = inode_find (itable, iabuf->ia_gfid);
+        if (inode == NULL) {
+                inode = inode_new (itable);
+        }
+
+        linked_inode = inode_link (inode, parent, bname, iabuf);
+
+        inode_unref (inode);
+
+out:
+        return linked_inode;
+}
+
+int
+posix_make_ancestral_node (const char *priv_base_path, char *path, int pathsize,
+                           gf_dirent_t *head,
+                           char *dir_name, struct iatt *iabuf, inode_t *inode,
+                           int type, dict_t *xdata)
+{
+        gf_dirent_t *entry           = NULL;
+        char real_path[PATH_MAX + 1] = {0, }, len = 0;
+        loc_t        loc             = {0, };
+        int          ret             = -1;
+
+        len = strlen (path) + strlen (dir_name) + 1;
+        if (len > pathsize) {
+                goto out;
+        }
+
+        strcat (path, dir_name);
+
+        if (type & POSIX_ANCESTRY_DENTRY) {
+                entry = gf_dirent_for_name (dir_name);
+                if (!entry) {
+                        gf_log (THIS->name, GF_LOG_ERROR,
+                                "could not create gf_dirent for entry %s: (%s)",
+                                dir_name, strerror (errno));
+                        goto out;
+                }
+
+                entry->d_stat = *iabuf;
+                entry->inode = inode_ref (inode);
+
+                list_add_tail (&entry->list, &head->list);
+                strcpy (real_path, priv_base_path);
+                strcat (real_path, "/");
+                strcat (real_path, path);
+                loc.inode = inode_ref (inode);
+                uuid_copy (loc.gfid, inode->gfid);
+
+                entry->dict = posix_lookup_xattr_fill (THIS, real_path, &loc,
+                                                       xdata, iabuf);
+                loc_wipe (&loc);
+        }
+
+        ret = 0;
+
+out:
+        return ret;
+}
+
+int
+posix_make_ancestryfromgfid (xlator_t *this, char *path, int pathsize,
+                             gf_dirent_t *head, int type, uuid_t gfid,
+                             const size_t handle_size,
+                             const char *priv_base_path, inode_table_t *itable,
+                             inode_t **parent, dict_t *xdata)
+{
+        char        *linkname   = NULL; /* "../../<gfid[0]>/<gfid[1]/"
+                                         "<gfidstr>/<NAME_MAX>" */
+        char        *dir_handle = NULL;
+        char        *dir_name   = NULL;
+        char        *pgfidstr   = NULL;
+        char        *saveptr    = NULL;
+        ssize_t       len        = 0;
+        inode_t     *inode      = NULL;
+        struct iatt  iabuf      = {0, };
+        int          ret        = -1;
+        uuid_t       tmp_gfid   = {0, };
+
+        if (!path || !parent || !priv_base_path || uuid_is_null (gfid)) {
+                goto out;
+        }
+
+        if (__is_root_gfid (gfid)) {
+                if (parent) {
+                        if (*parent) {
+                                inode_unref (*parent);
+                        }
+
+                        *parent = inode_ref (itable->root);
+                }
+
+                inode = itable->root;
+
+                memset (&iabuf, 0, sizeof (iabuf));
+                uuid_copy (iabuf.ia_gfid, inode->gfid);
+                iabuf.ia_type = inode->ia_type;
+
+                ret = posix_make_ancestral_node (priv_base_path, path, pathsize,
+                                                 head, "/", &iabuf, inode, type,
+                                                 xdata);
+                return ret;
+        }
+
+        dir_handle = alloca (handle_size);
+        linkname   = alloca (PATH_MAX);
+        snprintf (dir_handle, handle_size, "%s/%s/%02x/%02x/%s",
+                  priv_base_path, HANDLE_PFX, gfid[0], gfid[1],
+                  uuid_utoa (gfid));
+
+        len = readlink (dir_handle, linkname, PATH_MAX);
+        if (len < 0) {
+                gf_log (this->name, GF_LOG_ERROR, "could not read the link "
+                        "from the gfid handle %s (%s)", dir_handle,
+                        strerror (errno));
+                goto out;
+        }
+
+        linkname[len] = '\0';
+
+        pgfidstr = strtok_r (linkname + SLEN("../../00/00/"), "/", &saveptr);
+        dir_name = strtok_r (NULL, "/", &saveptr);
+        strcat (dir_name, "/");
 
-#define HANDLE_PFX ".glusterfs"
-#define TRASH_DIR "landfill"
+        uuid_parse (pgfidstr, tmp_gfid);
+
+        ret = posix_make_ancestryfromgfid (this, path, pathsize, head, type,
+                                           tmp_gfid, handle_size,
+                                           priv_base_path, itable, parent,
+                                           xdata);
+        if (ret < 0) {
+                goto out;
+        }
 
-#define UUID0_STR "00000000-0000-0000-0000-000000000000"
-#define SLEN(str) (sizeof(str) - 1)
+        memset (&iabuf, 0, sizeof (iabuf));
 
+        inode = posix_resolve (this, itable, *parent, dir_name, &iabuf);
+
+        ret = posix_make_ancestral_node (priv_base_path, path, pathsize, head,
+                                         dir_name, &iabuf, inode, type, xdata);
+        if (*parent != NULL) {
+                inode_unref (*parent);
+        }
+
+        *parent = inode;
+
+out:
+        return ret;
+}
 
 int
 posix_handle_relpath (xlator_t *this, uuid_t gfid, const char *basename,