core/memacct: save allocs in mem_acct_rec list

With configure --enable-debug, add all object allocations
to a list in the corresponding mem_acct_rec. This
allows us to see all objects of a particular type
and allows for additional debugging in case of memory
leaks.

This is not compiled in by default and must be explicitly
enabled. It is intended to be used by developers.

> Change-Id: I7cf2dbeadecf994423d7e7591e85f18d2575cce8
> BUG: 1522662
> Signed-off-by: N Balachandran <nbalacha@redhat.com>

(cherry picked from commit 47d01546a1826dc14a8331ea8700015f1cfdc4db)
Change-Id: I7cf2dbeadecf994423d7e7591e85f18d2575cce8
BUG: 1523456
Signed-off-by: N Balachandran <nbalacha@redhat.com>

4 files changed, 61 insertions, 1 deletions

diff --git a/doc/debugging/mem-alloc-list.md b/doc/debugging/mem-alloc-list.md
new file mode 100644
index 00000000000..1c68e65d323
--- /dev/null
+++ b/doc/debugging/mem-alloc-list.md
@@ -0,0 +1,19 @@
+## Viewing Memory Allocations
+
+While statedumps provide stats of the number of allocations, size etc for a
+particular mem type, there is no easy way to examine all the allocated objects of that type
+in memory.Being able to view this information could help with determining how an object is used,
+and if there are any memory leaks.
+
+The mem_acct_rec structures have been updated to include lists to which the allocated object is
+added. These can be examined in gdb using simple scripts.
+
+`gdb> plist xl->mem_acct.rec[$type]->obj_list`
+
+will print out the pointers of all allocations of $type.
+
+These changes are primarily targeted at developers and need to enabled
+at compile-time using `configure --enable-debug`.
+
+
+
diff --git a/libglusterfs/src/mem-pool.c b/libglusterfs/src/mem-pool.c
index a972f67bb17..252bae5d7e3 100644
--- a/libglusterfs/src/mem-pool.c
+++ b/libglusterfs/src/mem-pool.c
@@ -78,8 +78,16 @@ gf_mem_set_acct_info (xlator_t *xl, char **alloc_ptr, size_t size,
         header->mem_acct = xl->mem_acct;
         header->magic = GF_MEM_HEADER_MAGIC;
 
+#ifdef DEBUG
+        INIT_LIST_HEAD(&header->acct_list);
+        LOCK(&xl->mem_acct->rec[type].lock);
+        {
+                list_add (&header->acct_list,
+                          &(xl->mem_acct->rec[type].obj_list));
+        }
+        UNLOCK(&xl->mem_acct->rec[type].lock);
+#endif
         ptr += sizeof (struct mem_header);
-
         /* data follows in this gap of 'size' bytes */
         *(uint32_t *) (ptr + size) = GF_MEM_TRAILER_MAGIC;
 
@@ -157,6 +165,27 @@ __gf_realloc (void *ptr, size_t size)
         GF_ASSERT (old_header->magic == GF_MEM_HEADER_MAGIC);
         tmp_header = *old_header;
 
+#ifdef DEBUG
+        int type = 0;
+        size_t copy_size = 0;
+
+        /* Making these changes for realloc is not straightforward. So
+         * I am simulating realloc using calloc and free
+         */
+
+        type = tmp_header.type;
+        new_ptr = __gf_calloc (1, size, type,
+                               tmp_header.mem_acct->rec[type].typestr);
+        if (new_ptr) {
+                copy_size = (size > tmp_header.size) ? tmp_header.size : size;
+                memcpy (new_ptr, ptr, copy_size);
+                __gf_free (ptr);
+        }
+
+        /* This is not quite what the man page says should happen */
+        return new_ptr;
+#endif
+
         tot_size = size + GF_MEM_HEADER_SIZE + GF_MEM_TRAILER_SIZE;
         new_ptr = realloc (old_header, tot_size);
         if (!new_ptr) {
@@ -313,6 +342,9 @@ __gf_free (void *free_ptr)
                  * to NULL */
                 if (!mem_acct->rec[header->type].num_allocs)
                         mem_acct->rec[header->type].typestr = NULL;
+#ifdef DEBUG
+                list_del (&header->acct_list);
+#endif
         }
         UNLOCK (&mem_acct->rec[header->type].lock);
 
diff --git a/libglusterfs/src/mem-pool.h b/libglusterfs/src/mem-pool.h
index e68e00dfca1..a2a907a2344 100644
--- a/libglusterfs/src/mem-pool.h
+++ b/libglusterfs/src/mem-pool.h
@@ -46,6 +46,9 @@ struct mem_acct_rec {
         uint32_t        total_allocs;
         uint32_t        max_num_allocs;
         gf_lock_t       lock;
+#ifdef DEBUG
+        struct list_head   obj_list;
+#endif
 };
 
 struct mem_acct {
@@ -59,6 +62,9 @@ struct mem_header {
         size_t          size;
         struct mem_acct *mem_acct;
         uint32_t        magic;
+#ifdef DEBUG
+        struct list_head   acct_list;
+#endif
         int             padding[8];
 };
 
diff --git a/libglusterfs/src/xlator.c b/libglusterfs/src/xlator.c
index de97dff6dfe..a6f83a22681 100644
--- a/libglusterfs/src/xlator.c
+++ b/libglusterfs/src/xlator.c
@@ -604,6 +604,9 @@ xlator_mem_acct_init (xlator_t *xl, int num_types)
                 if (ret) {
                         fprintf(stderr, "Unable to lock..errno : %d",errno);
                 }
+#ifdef DEBUG
+                INIT_LIST_HEAD(&(xl->mem_acct->rec[i].obj_list));
+#endif
         }
 
         return 0;