Add memory limiting capability to talloc

By calling talloc_set_memlimit() we can now set a max memory limit
for a whole talloc hierarchy.
ANy attempt to allocate memory beyond the max allowed for the whole
hierarchy wil cause an allocation failure.

Stealing memory correctly accounts for used memory in the old and the new
hierarchy but exceeding the memory limit in the new parent will not cause
a failure.

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/talloc/talloc.h b/lib/talloc/talloc.h
index e48dc09a40..f3cbcd0e7c 100644
--- a/lib/talloc/talloc.h
+++ b/lib/talloc/talloc.h
@@ -1842,6 +1842,25 @@ void talloc_set_log_fn(void (*log_fn)(const char *message));
  */
 void talloc_set_log_stderr(void);
 
+/**
+ * @brief Set a max memory limit for the current context hierarchy
+ *	  This affects all children of this context and constrain any
+ *	  allocation in the hierarchy to never exceed the limit set.
+ *	  The limit can be removed by setting 0 (unlimited) as the
+ *	  max_size by calling the funciton again on the sam context.
+ *	  Memory limits can also be nested, meaning a hild can have
+ *	  a stricter memory limit than a parent.
+ *	  Memory limits are enforced only at memory allocation time.
+ *	  Stealing a context into a 'limited' hierarchy properly
+ *	  updates memory usage but does *not* cause failure if the
+ *	  move causes the new parent to exceed its limits. However
+ *	  any further allocation on that hierarchy will then fail.
+ *
+ * @param[in]	ctx		The talloc context to set the limit on
+ * @param[in]	max_size	The (new) max_size
+ */
+int talloc_set_memlimit(const void *ctx, size_t max_size);
+
 /* @} ******************************************************************/
 
 #if TALLOC_DEPRECATED