Commit ae65a521 authored by Vlastimil Babka's avatar Vlastimil Babka

mm/slab: document kfree() as allowed for kmem_cache_alloc() objects

This will make it easier to free objects in situations when they can
come from either kmalloc() or kmem_cache_alloc(), and also allow
kfree_rcu() for freeing objects from kmem_cache_alloc().

For the SLAB and SLUB allocators this was always possible so with SLOB
gone, we can document it as supported.
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
parent 6630e950
......@@ -170,7 +170,16 @@ should be used if a part of the cache might be copied to the userspace.
After the cache is created kmem_cache_alloc() and its convenience
wrappers can allocate memory from that cache.
When the allocated memory is no longer needed it must be freed. You can
use kvfree() for the memory allocated with `kmalloc`, `vmalloc` and
`kvmalloc`. The slab caches should be freed with kmem_cache_free(). And
don't forget to destroy the cache with kmem_cache_destroy().
When the allocated memory is no longer needed it must be freed.
Objects allocated by `kmalloc` can be freed by `kfree` or `kvfree`. Objects
allocated by `kmem_cache_alloc` can be freed with `kmem_cache_free`, `kfree`
or `kvfree`, where the latter two might be more convenient thanks to not
needing the kmem_cache pointer.
The same rules apply to _bulk and _rcu flavors of freeing functions.
Memory allocated by `vmalloc` can be freed with `vfree` or `kvfree`.
Memory allocated by `kvmalloc` can be freed with `kvfree`.
Caches created by `kmem_cache_create` should be freed with
`kmem_cache_destroy` only after freeing all the allocated objects first.
......@@ -976,8 +976,10 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
* either fall back to use of call_rcu() or rearrange the structure to
* position the rcu_head structure into the first 4096 bytes.
*
* Note that the allowable offset might decrease in the future, for example,
* to allow something like kmem_cache_free_rcu().
* The object to be freed can be allocated either by kmalloc() or
* kmem_cache_alloc().
*
* Note that the allowable offset might decrease in the future.
*
* The BUILD_BUG_ON check must not involve any function calls, hence the
* checks are done in macros here.
......
......@@ -989,12 +989,9 @@ EXPORT_SYMBOL(__kmalloc_node_track_caller);
/**
* kfree - free previously allocated memory
* @object: pointer returned by kmalloc.
* @object: pointer returned by kmalloc() or kmem_cache_alloc()
*
* If @object is NULL, no operation is performed.
*
* Don't free memory not originally allocated by kmalloc()
* or you will run into trouble.
*/
void kfree(const void *object)
{
......
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