core: GFID filehandle based backend and anonymous FDs

1. What
--------
This change introduces an infrastructure change in the filesystem
which lets filesystem operation address objects (inodes) just by its
GFID. Thus far GFID has been a unique identifier of a user-visible
inode. But in terms of addressability the only mechanism thus far has
been the backend filesystem path, which could be derived from the
GFID only if it was cached in the inode table along with the entire set
of dentry ancestry leading up to the root.

This change essentially decouples addressability from the namespace. It
is no more necessary to be aware of the parent directory to address a
file or directory.

2. Why
-------
The biggest use case for such a feature is NFS for generating
persistent filehandles. So far the technique for generating filehandles
in NFS has been to encode path components so that the appropriate
inode_t can be repopulated into the inode table by means of a recursive
lookup of each component top-down.

Another use case is the ability to perform more intelligent self-healing
and rebalancing of inodes with hardlinks and also to detect renames.

A derived feature from GFID filehandles is anonymous FDs. An anonymous FD
is an internal USABLE "fd_t" which does not map to a user opened file
descriptor or to an internal ->open()'d fd. The ability to address a file
by the GFID eliminates the need to have a persistent ->open()'d fd for the
purpose of avoiding the namespace. This improves NFS read/write performance
significantly eliminating open/close calls and also fixes some of today's
limitations (like keeping an FD open longer than necessary resulting
in disk space leakage)

3. How
-------

At each storage/posix translator level, every file is hardlinked inside
a hidden .glusterfs directory (under the top level export) with the name
as the ascii-encoded standard UUID format string. For reasons of performance
and scalability there is a two-tier classification of those hardlinks
under directories with the initial parts of the UUID string as the directory
names.

For directories (which cannot be hardlinked), the approach is to use a symlink
which dereferences the parent GFID path along with basename of the directory.
The parent GFID dereference will in turn be a dereference of the grandparent
with the parent's basename, and so on recursively up to the root export.

4. Development
---------------

4a. To leverage the ability to address an inode by its GFID, the technique is
to perform a "nameless lookup". This means, to populate a loc_t structure as:

loc_t {
   pargfid: NULL
   parent: NULL
   name: NULL
   path: NULL
   gfid: GFID to be looked up [out parameter]
   inode: inode_new () result [in parameter]
}

and performing such lookup will return in its callback an inode_t
populated with the right contexts and a struct iatt which can be
used to perform an inode_link () on the inode (without a parent and
basename). The inode will now be hashed and linked in the inode table
and findable via inode_find().

A fundamental change moving forward is that the primary fields in a
loc_t structure are now going to be (pargfid, name) and (gfid) depending
on the kind of FOP. So far path had been the primary field for operations.
The remaining fields only serve as hints/helpers.

4b. If read/write is to be performed on an inode_t, the approach so far
has been to: fd_create(), STACK_WIND(open, fd), fd_bind (in callback) and
then perform STACK_WIND(read, fd) etc. With anonymous fds now you can do
fd_anonymous (inode), STACK_WIND (read, fd). This results in great boost
in performance in the inbuilt NFS server.

5. Misc
-------
The inode_ctx_put[2] has been renamed to inode_ctx_set[2] to be consistent
with the rest of the codebase.

Change-Id: Ie4629edf6bd32a595f4d7f01e90c0a01f16fb12f
BUG: 781318
Reviewed-on: http://review.gluster.com/669
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@gluster.com>

1 files changed, 166 insertions, 222 deletions

diff --git a/xlators/protocol/server/src/server-resolve.c b/xlators/protocol/server/src/server-resolve.c
index 50ae9231c33..38ab368c3f0 100644
--- a/xlators/protocol/server/src/server-resolve.c
+++ b/xlators/protocol/server/src/server-resolve.c
@@ -33,72 +33,9 @@ resolve_entry_simple (call_frame_t *frame);
 int
 resolve_inode_simple (call_frame_t *frame);
 int
-resolve_path_simple (call_frame_t *frame);
-
+resolve_continue (call_frame_t *frame);
 int
-component_count (const char *path)
-{
-        int         count = 0;
-        const char *trav = NULL;
-
-        for (trav = path; *trav; trav++) {
-                if (*trav == '/')
-                        count++;
-        }
-
-        return count + 2;
-}
-
-
-int
-prepare_components (call_frame_t *frame)
-{
-        server_state_t       *state = NULL;
-        server_resolve_t     *resolve = NULL;
-        char                 *resolved = NULL;
-        int                   count = 0;
-        struct resolve_comp  *components = NULL;
-        int                   i = 0;
-        char                 *trav = NULL;
-
-        state = CALL_STATE (frame);
-        resolve = state->resolve_now;
-
-        resolved = gf_strdup (resolve->path);
-        resolve->resolved = resolved;
-
-        count = component_count (resolve->path);
-        components = GF_CALLOC (sizeof (*components), count,
-                                gf_server_mt_resolv_comp_t);
-        if (!components)
-                goto out;
-
-        resolve->components = components;
-
-        components[0].basename = "";
-        components[0].inode    = state->itable->root;
-
-        i = 1;
-        for (trav = resolved; *trav; trav++) {
-                if (*trav == '/') {
-                        *trav = 0;
-
-                        if (!(*(trav + 1))) {
-                                /* Skip trailing "/" in a path.
-                                   This is the check which prevents
-                                   inode_link'age of itable->root
-                                */
-                                break;
-                        }
-
-                        components[i].basename = trav + 1;
-                        i++;
-                }
-        }
-out:
-        return 0;
-}
-
+resolve_anonfd_simple (call_frame_t *frame);
 
 int
 resolve_loc_touchup (call_frame_t *frame)
@@ -123,231 +60,177 @@ resolve_loc_touchup (call_frame_t *frame)
                 if (ret)
                         gf_log (frame->this->name, GF_LOG_TRACE,
                                 "return value inode_path %d", ret);
-
-                if (!path)
-                        path = gf_strdup (resolve->path);
-
                 loc->path = path;
         }
 
-        loc->name = strrchr (loc->path, '/');
-        if (loc->name)
-                loc->name++;
-
-        if (!loc->parent && loc->inode) {
-                loc->parent = inode_parent (loc->inode, 0, NULL);
-        }
-
         return 0;
 }
 
 
 int
-resolve_deep_continue (call_frame_t *frame)
+resolve_gfid_entry_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                        int op_ret, int op_errno, inode_t *inode,
+                        struct iatt *buf, dict_t *xattr, struct iatt *postparent)
 {
         server_state_t       *state = NULL;
-        xlator_t             *this = NULL;
         server_resolve_t     *resolve = NULL;
-        int                   ret = 0;
+        inode_t              *link_inode = NULL;
+        loc_t                *resolve_loc = NULL;
 
         state = CALL_STATE (frame);
-        this  = frame->this;
         resolve = state->resolve_now;
+        resolve_loc = &resolve->resolve_loc;
 
-        resolve->op_ret   = 0;
-        resolve->op_errno = 0;
+        if (op_ret == -1) {
+                gf_log (this->name, ((op_errno == ENOENT) ? GF_LOG_DEBUG :
+                                     GF_LOG_WARNING),
+                        "%s/%s: failed to resolve (%s)",
+                        uuid_utoa (resolve_loc->pargfid), resolve_loc->name,
+                        strerror (op_errno));
+                goto out;
+        }
 
-        if (!uuid_is_null (resolve->pargfid))
-                ret = resolve_entry_simple (frame);
-        else if (!uuid_is_null (resolve->gfid))
-                ret = resolve_inode_simple (frame);
-        else if (resolve->path)
-                ret = resolve_path_simple (frame);
-        if (ret)
-                gf_log (this->name, GF_LOG_DEBUG,
-                        "return value of resolve_*_simple %d", ret);
+        link_inode = inode_link (inode, resolve_loc->parent,
+                                 resolve_loc->name, buf);
 
-        resolve_loc_touchup (frame);
+        if (!link_inode)
+                goto out;
 
-        server_resolve_all (frame);
+        inode_lookup (link_inode);
+
+        inode_unref (link_inode);
 
+out:
+        loc_wipe (resolve_loc);
+
+        resolve_continue (frame);
         return 0;
 }
 
 
 int
-resolve_deep_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+resolve_gfid_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
                   int op_ret, int op_errno, inode_t *inode, struct iatt *buf,
                   dict_t *xattr, struct iatt *postparent)
 {
         server_state_t       *state = NULL;
         server_resolve_t     *resolve = NULL;
-        struct resolve_comp  *components = NULL;
-        int                   i = 0;
         inode_t              *link_inode = NULL;
+        loc_t                *resolve_loc = NULL;
 
         state = CALL_STATE (frame);
         resolve = state->resolve_now;
-        components = resolve->components;
-
-        i = (long) cookie;
+        resolve_loc = &resolve->resolve_loc;
 
         if (op_ret == -1) {
                 gf_log (this->name, ((op_errno == ENOENT) ? GF_LOG_DEBUG :
                                      GF_LOG_WARNING),
                         "%s: failed to resolve (%s)",
-                        resolve->resolved, strerror (op_errno));
-                goto get_out_of_here;
+                        uuid_utoa (resolve_loc->gfid), strerror (op_errno));
+                loc_wipe (&resolve->resolve_loc);
+                goto out;
         }
 
-        if (i != 0) {
-                /* no linking for root inode */
-                link_inode = inode_link (inode, resolve->deep_loc.parent,
-                                         resolve->deep_loc.name, buf);
-                inode_lookup (link_inode);
-                components[i].inode  = link_inode;
-                link_inode = NULL;
-        }
+        loc_wipe (resolve_loc);
 
-        loc_wipe (&resolve->deep_loc);
+        link_inode = inode_link (inode, NULL, NULL, buf);
 
-        i++; /* next component */
+        if (!link_inode)
+                goto out;
 
-        if (!components[i].basename) {
-                /* all components of the path are resolved */
-                goto get_out_of_here;
+        inode_lookup (link_inode);
+
+        if (uuid_is_null (resolve->pargfid)) {
+                inode_unref (link_inode);
+                goto out;
         }
 
-        /* join the current component with the path resolved until now */
-        *(components[i].basename - 1) = '/';
+        resolve_loc->parent = link_inode;
+        uuid_copy (resolve_loc->pargfid, resolve_loc->parent->gfid);
 
-        resolve->deep_loc.path   = gf_strdup (resolve->resolved);
-        resolve->deep_loc.parent = inode_ref (components[i-1].inode);
-        resolve->deep_loc.inode  = inode_new (state->itable);
-        resolve->deep_loc.name   = components[i].basename;
+        resolve_loc->name = resolve->bname;
 
-        if (frame && frame->root->state && BOUND_XL (frame)) {
-                STACK_WIND_COOKIE (frame, resolve_deep_cbk, (void *) (long) i,
-                                   BOUND_XL (frame), BOUND_XL (frame)->fops->lookup,
-                                   &resolve->deep_loc, NULL);
-                return 0;
-        }
+        resolve_loc->inode = inode_new (state->itable);
+        inode_path (resolve_loc->parent, resolve_loc->name,
+                    (char **) &resolve_loc->path);
 
-get_out_of_here:
-        resolve_deep_continue (frame);
+        STACK_WIND (frame, resolve_gfid_entry_cbk,
+                    BOUND_XL (frame), BOUND_XL (frame)->fops->lookup,
+                    &resolve->resolve_loc, NULL);
+        return 0;
+out:
+        resolve_continue (frame);
         return 0;
 }
 
 
 int
-resolve_path_deep (call_frame_t *frame)
+resolve_gfid (call_frame_t *frame)
 {
-        server_state_t     *state = NULL;
-        server_resolve_t   *resolve = NULL;
-        int                 i = 0;
+        server_state_t       *state = NULL;
+        xlator_t             *this = NULL;
+        server_resolve_t     *resolve = NULL;
+        loc_t                *resolve_loc = NULL;
+        int                   ret = 0;
 
         state = CALL_STATE (frame);
+        this  = frame->this;
         resolve = state->resolve_now;
+        resolve_loc = &resolve->resolve_loc;
 
-        gf_log (BOUND_XL (frame)->name, GF_LOG_DEBUG,
-                "RESOLVE %s() seeking deep resolution of %s",
-                gf_fop_list[frame->root->op], resolve->path);
-
-        prepare_components (frame);
-
-        /* start from the root */
-        resolve->deep_loc.inode = state->itable->root;
-        resolve->deep_loc.path  = gf_strdup ("/");
-        resolve->deep_loc.name  = "";
-
-        if (frame && frame->root->state && BOUND_XL (frame)) {
-                STACK_WIND_COOKIE (frame, resolve_deep_cbk, (void *) (long) i,
-                                   BOUND_XL (frame), BOUND_XL (frame)->fops->lookup,
-                                   &resolve->deep_loc, NULL);
-                return 0;
+        if (!uuid_is_null (resolve->pargfid)) {
+                uuid_copy (resolve_loc->gfid, resolve->pargfid);
+                resolve_loc->inode = inode_new (state->itable);
+                ret = inode_path (resolve_loc->inode, NULL,
+                                  (char **)&resolve_loc->path);
+        } else if (!uuid_is_null (resolve->gfid)) {
+                uuid_copy (resolve_loc->gfid, resolve->gfid);
+                resolve_loc->inode = inode_new (state->itable);
+                ret = inode_path (resolve_loc->inode, NULL,
+                                  (char **)&resolve_loc->path);
         }
 
-        resolve_deep_continue (frame);
+        STACK_WIND (frame, resolve_gfid_cbk,
+                    BOUND_XL (frame), BOUND_XL (frame)->fops->lookup,
+                    &resolve->resolve_loc, NULL);
         return 0;
 }
 
 
 int
-resolve_path_simple (call_frame_t *frame)
+resolve_continue (call_frame_t *frame)
 {
         server_state_t       *state = NULL;
+        xlator_t             *this = NULL;
         server_resolve_t     *resolve = NULL;
-        struct resolve_comp  *components = NULL;
-        int                   ret = -1;
-        int                   par_idx = -1;
-        int                   ino_idx = -1;
-        int                   i = 0;
+        int                   ret = 0;
 
         state = CALL_STATE (frame);
+        this  = frame->this;
         resolve = state->resolve_now;
-        components = resolve->components;
-
-        if (!components) {
-                gf_log ("", GF_LOG_INFO,
-                        "failed to resolve, component not found");
-                resolve->op_ret   = -1;
-                resolve->op_errno = ENOENT;
-                goto out;
-        }
 
-        for (i = 0; components[i].basename; i++) {
-                par_idx = ino_idx;
-                ino_idx = i;
-        }
-
-        if (ino_idx == -1) {
-                gf_log ("", GF_LOG_INFO,
-                        "failed to resolve, inode index not found");
-                resolve->op_ret  = -1;
-                resolve->op_errno = EINVAL;
-                goto out;
-        }
-
-        if (par_idx == -1)
-                /* "/" will not have a parent */
-                goto noparent;
-
-        if (!components[par_idx].inode) {
-                gf_log ("", GF_LOG_INFO,
-                        "failed to resolve, parent inode not found");
-                resolve->op_ret    = -1;
-                resolve->op_errno  = ENOENT;
-                goto out;
-        }
-        state->loc_now->parent = inode_ref (components[par_idx].inode);
-noparent:
-
-        if (!components[ino_idx].inode &&
-            (resolve->type == RESOLVE_MUST || resolve->type == RESOLVE_EXACT)) {
-                gf_log ("", GF_LOG_INFO,
-                        "failed to resolve, inode not found");
-                resolve->op_ret    = -1;
-                resolve->op_errno  = ENOENT;
-                goto out;
-        }
+        resolve->op_ret   = 0;
+        resolve->op_errno = 0;
 
-        if (components[ino_idx].inode && resolve->type == RESOLVE_NOT) {
-                gf_log ("", GF_LOG_INFO,
-                        "failed to resolve, inode found");
-                resolve->op_ret    = -1;
-                resolve->op_errno  = EEXIST;
+        if (resolve->fd_no != -1) {
+                ret = resolve_anonfd_simple (frame);
                 goto out;
-        }
-
-        if (components[ino_idx].inode)
-                state->loc_now->inode  = inode_ref (components[ino_idx].inode);
-
-        ret = 0;
+        } else if (!uuid_is_null (resolve->pargfid))
+                ret = resolve_entry_simple (frame);
+        else if (!uuid_is_null (resolve->gfid))
+                ret = resolve_inode_simple (frame);
+        if (ret)
+                gf_log (this->name, GF_LOG_DEBUG,
+                        "return value of resolve_*_simple %d", ret);
 
+        resolve_loc_touchup (frame);
 out:
-        return ret;
+        server_resolve_all (frame);
+
+        return 0;
 }
 
+
 /*
   Check if the requirements are fulfilled by entries in the inode cache itself
   Return value:
@@ -380,7 +263,9 @@ resolve_entry_simple (call_frame_t *frame)
         }
 
         /* expected @parent was found from the inode cache */
+        uuid_copy (state->loc_now->pargfid, resolve->pargfid);
         state->loc_now->parent = inode_ref (parent);
+        state->loc_now->name = resolve->bname;
 
         inode = inode_grep (state->itable, parent, resolve->bname);
         if (!inode) {
@@ -441,7 +326,7 @@ server_resolve_entry (call_frame_t *frame)
 
         if (ret > 0) {
                 loc_wipe (loc);
-                resolve_path_deep (frame);
+                resolve_gfid (frame);
                 return 0;
         }
 
@@ -477,6 +362,7 @@ resolve_inode_simple (call_frame_t *frame)
         ret = 0;
 
         state->loc_now->inode = inode_ref (inode);
+        uuid_copy (state->loc_now->gfid, resolve->gfid);
 
 out:
         if (inode)
@@ -500,7 +386,7 @@ server_resolve_inode (call_frame_t *frame)
 
         if (ret > 0) {
                 loc_wipe (loc);
-                resolve_path_deep (frame);
+                resolve_gfid (frame);
                 return 0;
         }
 
@@ -514,6 +400,62 @@ server_resolve_inode (call_frame_t *frame)
 
 
 int
+resolve_anonfd_simple (call_frame_t *frame)
+{
+        server_state_t     *state = NULL;
+        server_resolve_t   *resolve = NULL;
+        inode_t            *inode = NULL;
+        int                 ret = 0;
+
+        state = CALL_STATE (frame);
+        resolve = state->resolve_now;
+
+        inode = inode_find (state->itable, resolve->gfid);
+
+        if (!inode) {
+                resolve->op_ret   = -1;
+                resolve->op_errno = ENOENT;
+                ret = 1;
+                goto out;
+        }
+
+        ret = 0;
+
+        state->fd = fd_anonymous (inode);
+out:
+        if (inode)
+                inode_unref (inode);
+
+        return ret;
+}
+
+
+int
+server_resolve_anonfd (call_frame_t *frame)
+{
+        server_state_t     *state = NULL;
+        int                 ret = 0;
+        loc_t              *loc = NULL;
+
+        state = CALL_STATE (frame);
+        loc  = state->loc_now;
+
+        ret = resolve_anonfd_simple (frame);
+
+        if (ret > 0) {
+                loc_wipe (loc);
+                resolve_gfid (frame);
+                return 0;
+        }
+
+        server_resolve_all (frame);
+
+        return 0;
+
+}
+
+
+int
 server_resolve_fd (call_frame_t *frame)
 {
         server_state_t       *state = NULL;
@@ -527,6 +469,11 @@ server_resolve_fd (call_frame_t *frame)
 
         fd_no = resolve->fd_no;
 
+        if (fd_no == -2) {
+                server_resolve_anonfd (frame);
+                return 0;
+        }
+
         state->fd = gf_fd_fdptr_get (conn->fdtable, fd_no);
 
         if (!state->fd) {
@@ -562,14 +509,11 @@ server_resolve (call_frame_t *frame)
 
                 server_resolve_inode (frame);
 
-        } else if (resolve->path) {
-
-                gf_log (frame->this->name, GF_LOG_INFO,
-                        "pure path resolution for %s (%s)",
-                        resolve->path, gf_fop_list[frame->root->op]);
-                resolve_path_deep (frame);
-
-        } else  {
+        } else {
+                if (resolve == &state->resolve)
+                        gf_log (frame->this->name, GF_LOG_WARNING,
+                                "no resolution type for %s (%s)",
+                                resolve->path, gf_fop_list[frame->root->op]);
 
                 resolve->op_ret = -1;
                 resolve->op_errno = EINVAL;