stack: use list_head for managing frames

PROBLEM
--------

statedump requests that traverse call frames of all call stacks in
execution may race with a STACK_RESET on a stack.  This could crash the
corresponding glusterfs process. For e.g, recently we observed this in a
regression test case tests/basic/afr/sparse-self-heal.t.

FIX
---

gf_proc_dump_pending_frames takes a (TRY_LOCK) call_pool->lock before
iterating through call frames of all call stacks in progress.  With this
fix, STACK_RESET removes its call frames under the same lock.

Additional info
----------------

This fix makes call_stack_t to use struct list_head in place of custom
doubly-linked list implementation. This makes call_frame_t manipulation
easier to maintain in the context of STACK_WIND et al.

BUG: 1234408
Change-Id: I7e43bccd3994cd9184ab982dba3dbc10618f0d94
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/11095
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
(cherry picked from commit 79e4c7b2fad6db15863efb4e979525b1bd4862ea)
Reviewed-on: http://review.gluster.org/11352

2 files changed, 6 insertions, 7 deletions

diff --git a/xlators/features/protect/src/prot_client.c b/xlators/features/protect/src/prot_client.c
index 500c772bedd..33c2b5af427 100644
--- a/xlators/features/protect/src/prot_client.c
+++ b/xlators/features/protect/src/prot_client.c
@@ -40,10 +40,9 @@ pcli_print_trace (char *name, call_frame_t *frame)
         int     i;
 
         gf_log (name, GF_LOG_INFO, "Translator stack:");
-        while (frame) {
+        list_for_each_entry (frame, &frame->root->myframes, frames) {
                 gf_log (name, GF_LOG_INFO, "%s (%s)",
                         frame->wind_from, frame->this->name);
-                frame = frame->next;
         }
 
         size = backtrace (frames, NUM_FRAMES);
@@ -82,7 +81,7 @@ pcli_rename (call_frame_t *frame, xlator_t *this, loc_t *oldloc,
         if (value != PROT_ACT_NONE) {
                 gf_log (this->name, GF_LOG_WARNING,
                         "got rename for protected %s", oldloc->path);
-                pcli_print_trace (this->name, frame->next);
+                pcli_print_trace (this->name, frame);
                 if (value == PROT_ACT_REJECT) {
                         STACK_UNWIND_STRICT (rename, frame, -1, EPERM,
                                              NULL, NULL, NULL, NULL, NULL,
@@ -166,7 +165,7 @@ pcli_unlink (call_frame_t *frame, xlator_t *this, loc_t *loc, int xflag,
         if (value != PROT_ACT_NONE) {
                 gf_log (this->name, GF_LOG_WARNING,
                         "got unlink for protected %s", loc->path);
-                pcli_print_trace(this->name,frame->next);
+                pcli_print_trace(this->name, frame);
                 if (value == PROT_ACT_REJECT) {
                         STACK_UNWIND_STRICT (unlink, frame, -1, EPERM,
                                              NULL, NULL, NULL);
diff --git a/xlators/meta/src/frames-file.c b/xlators/meta/src/frames-file.c
index 0e9777c9da2..b81e5c7413b 100644
--- a/xlators/meta/src/frames-file.c
+++ b/xlators/meta/src/frames-file.c
@@ -44,8 +44,7 @@ frames_file_fill (xlator_t *this, inode_t *file, strfd_t *strfd)
                         strprintf (strfd, "\t\t\"Number\": %d,\n", ++i);
                         strprintf (strfd, "\t\t\"Frame\": [\n");
                         j = 1;
-                        for (frame = &stack->frames; frame;
-                             frame = frame->next) {
+                        list_for_each_entry (frame, &stack->myframes, frames) {
                                 strprintf (strfd, "\t\t   {\n");
                                 strprintf (strfd, "\t\t\t\"Number\": %d,\n",
                                                 j++);
@@ -76,7 +75,8 @@ frames_file_fill (xlator_t *this, inode_t *file, strfd_t *strfd)
                                                         frame->unwind_to);
                                 strprintf (strfd, "\t\t\t\"Complete\": %d\n",
                                                 frame->complete);
-                                if (frame->next == NULL)
+                                if (list_is_last (&frame->frames,
+                                                  &stack->myframes))
                                         strprintf (strfd, "\t\t   }\n");
                                 else
                                         strprintf (strfd, "\t\t   },\n");