mm: kvmalloc: align kvrealloc() with krealloc()

Besides the obvious (and desired) difference between krealloc() and
kvrealloc(), there is some inconsistency in their function signatures and
behavior:

 - krealloc() frees the memory when the requested size is zero, whereas
   kvrealloc() simply returns a pointer to the existing allocation.

 - krealloc() behaves like kmalloc() if a NULL pointer is passed, whereas
   kvrealloc() does not accept a NULL pointer at all and, if passed,
   would fault instead.

 - krealloc() is self-contained, whereas kvrealloc() relies on the caller
   to provide the size of the previous allocation.

Inconsistent behavior throughout allocation APIs is error prone, hence
make kvrealloc() behave like krealloc(), which seems superior in all
mentioned aspects.

Besides that, implementing kvrealloc() by making use of krealloc() and
vrealloc() provides oppertunities to grow (and shrink) allocations more
efficiently.  For instance, vrealloc() can be optimized to allocate and
map additional pages to grow the allocation or unmap and free unused pages
to shrink the allocation.

[[email protected]: document concurrency restrictions]
  Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: disable KASAN when switching to vmalloc]
  Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: properly document __GFP_ZERO behavior]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Danilo Krummrich <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Chandan Babu R <[email protected]>
Cc: Christian König <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Hyeonggon Yoo <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Oliver Upton <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Wedson Almeida Filho <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c
index 2da094bdf8a4..18e366cc4993 100644
--- a/drivers/gpu/drm/drm_exec.c
+++ b/drivers/gpu/drm/drm_exec.c
@@ -145,8 +145,7 @@ static int drm_exec_obj_locked(struct drm_exec *exec,
 		size_t size = exec->max_objects * sizeof(void *);
 		void *tmp;
 
-		tmp = kvrealloc(exec->objects, size, size + PAGE_SIZE,
-				GFP_KERNEL);
+		tmp = kvrealloc(exec->objects, size + PAGE_SIZE, GFP_KERNEL);
 		if (!tmp)
 			return -ENOMEM;