core: Reduce calls to THIS wherever possible (gluster#2010)

In few functions 'THIS' is called inside a loop and saved for later
use in 'old_THIS'. Instead we can call 'THIS' only when 'old_THIS'
is NULL and reuse that itself to reduce redundant calls.

Change-Id: Ie5d4e5fe42bd4df02d101b4c199759cb84e6aee1
Fixes: gluster#1755
Signed-off-by: karthik-us <ksubrahm@redhat.com>

Author: karthik-us

heal/src/glfs-heal.c

@@ -1152,7 +1152,8 @@ glfsh_gather_heal_info(glfs_t *fs, xlator_t *top_subvol, loc_t *rootloc,
             !strstr(xl->name, "-ta-")) {
             heal_xl = _get_ancestor(xl, heal_op);
             if (heal_xl) {
-                old_THIS = THIS;
+                if (!old_THIS)
+                    old_THIS = THIS;
                 THIS = heal_xl;
                 ret = glfsh_print_pending_heals(
                     fs, top_subvol, rootloc, xl, heal_op,

libglusterfs/src/fd.c

@@ -462,22 +462,26 @@ fd_destroy(fd_t *fd, gf_boolean_t bound)
         for (i = 0; i < fd->xl_count; i++) {
             if (fd->_ctx[i].key) {
                 xl = fd->_ctx[i].xl_key;
-                old_THIS = THIS;
-                THIS = xl;
-                if (!xl->call_cleanup && xl->cbks->releasedir)
+                if (!xl->call_cleanup && xl->cbks->releasedir) {
+                    if (!old_THIS)
+                        old_THIS = THIS;
+                    THIS = xl;
                     xl->cbks->releasedir(xl, fd);
-                THIS = old_THIS;
+                    THIS = old_THIS;
+                }
             }
         }
     } else {
         for (i = 0; i < fd->xl_count; i++) {
             if (fd->_ctx[i].key) {
                 xl = fd->_ctx[i].xl_key;
-                old_THIS = THIS;
-                THIS = xl;
-                if (!xl->call_cleanup && xl->cbks->release)
+                if (!xl->call_cleanup && xl->cbks->release) {
+                    if (!old_THIS)
+                        old_THIS = THIS;
+                    THIS = xl;
                     xl->cbks->release(xl, fd);
-                THIS = old_THIS;
+                    THIS = old_THIS;
+                }
             }
         }
     }

libglusterfs/src/inode.c

@@ -343,7 +343,8 @@ __inode_ctx_free(inode_t *inode)
         if (inode->_ctx[index].value1 || inode->_ctx[index].value2) {
             xl = (xlator_t *)(long)inode->_ctx[index].xl_key;
             if (xl && !xl->call_cleanup && xl->cbks->forget) {
-                old_THIS = THIS;
+                if (!old_THIS)
+                    old_THIS = THIS;
                 THIS = xl;
                 xl->cbks->forget(xl, inode);
                 THIS = old_THIS;
@@ -391,11 +392,13 @@ inode_ctx_merge(fd_t *fd, inode_t *inode, inode_t *linked_inode)
         if (inode->_ctx[index].xl_key) {
             xl = (xlator_t *)(long)inode->_ctx[index].xl_key;
 
-            old_THIS = THIS;
-            THIS = xl;
-            if (xl->cbks->ictxmerge)
+            if (xl->cbks->ictxmerge) {
+                if (!old_THIS)
+                    old_THIS = THIS;
+                THIS = xl;
                 xl->cbks->ictxmerge(xl, fd, inode, linked_inode);
-            THIS = old_THIS;
+                THIS = old_THIS;
+            }
         }
     }
 }
@@ -1219,11 +1222,13 @@ inode_invalidate(inode_t *inode)
 
     xl = inode->table->xl->graph->first;
     while (xl) {
-        old_THIS = THIS;
-        THIS = xl;
-        if (xl->cbks->invalidate)
+        if (xl->cbks->invalidate) {
+            if (!old_THIS)
+                old_THIS = THIS;
+            THIS = xl;
             ret = xl->cbks->invalidate(xl, inode);
-        THIS = old_THIS;
+            THIS = old_THIS;
+        }
 
         if (ret)
             break;
@@ -2654,22 +2659,21 @@ inode_ctx_size(inode_t *inode)
                 continue;
 
             xl = (xlator_t *)(long)inode->_ctx[i].xl_key;
-            old_THIS = THIS;
-            THIS = xl;
 
             /* If inode ref is taken when THIS is global xlator,
              * the ctx xl_key is set, but the value is NULL.
              * For global xlator the cbks can be NULL, hence check
              * for the same */
-            if (!xl->cbks) {
-                THIS = old_THIS;
+            if (!xl->cbks)
                 continue;
-            }
 
-            if (xl->cbks->ictxsize)
+            if (xl->cbks->ictxsize) {
+                if (!old_THIS)
+                    old_THIS = THIS;
+                THIS = xl;
                 size += xl->cbks->ictxsize(xl, inode);
-
-            THIS = old_THIS;
+                THIS = old_THIS;
+            }
         }
     }
     UNLOCK(&inode->lock);