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Commit a8d05c81 authored by Eric Paris's avatar Eric Paris
Browse files

flex_array: allow 0 length elements 



flex_arrays are supposed to be a replacement for:
kmalloc(num_elements * sizeof(element))

If kmalloc is given 0 num_elements or a 0 size element it will happily return
ZERO_SIZE_PTR.  Which looks like a valid allocation, but which will explode if
something actually try to use it.  The current flex_array code will return an
equivalent result if num_elements is 0, but will fail to work if
sizeof(element) is 0.  This patch allows allocation to work even for 0 size
elements.  It will cause flex_arrays to explode though if they are used.
Imitating the kmalloc behavior.

Based-on-patch-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarEric Paris <eparis@redhat.com>
Acked-by: default avatarDave Hansen <dave@linux.vnet.ibm.com>
parent 150cdf6e

lib/flex_array.c

+20 −6
Original line number Diff line number Diff line
@@ -88,7 +88,10 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total, 
					gfp_t flags)

{

	struct flex_array *ret;

	int max_size = FLEX_ARRAY_NR_BASE_PTRS *

	int max_size = 0;



	if (element_size)

		max_size = FLEX_ARRAY_NR_BASE_PTRS *

			   FLEX_ARRAY_ELEMENTS_PER_PART(element_size);



	/* max_size will end up 0 if element_size > PAGE_SIZE */
@@ -183,15 +186,18 @@ __fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags) 
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,

			gfp_t flags)

{

	int part_nr = fa_element_to_part_nr(fa, element_nr);

	int part_nr;

	struct flex_array_part *part;

	void *dst;



	if (element_nr >= fa->total_nr_elements)

		return -ENOSPC;

	if (!fa->element_size)

		return 0;

	if (elements_fit_in_base(fa))

		part = (struct flex_array_part *)&fa->parts[0];

	else {

		part_nr = fa_element_to_part_nr(fa, element_nr);

		part = __fa_get_part(fa, part_nr, flags);

		if (!part)

			return -ENOMEM;
@@ -211,15 +217,18 @@ EXPORT_SYMBOL(flex_array_put); 
 */

int flex_array_clear(struct flex_array *fa, unsigned int element_nr)

{

	int part_nr = fa_element_to_part_nr(fa, element_nr);

	int part_nr;

	struct flex_array_part *part;

	void *dst;



	if (element_nr >= fa->total_nr_elements)

		return -ENOSPC;

	if (!fa->element_size)

		return 0;

	if (elements_fit_in_base(fa))

		part = (struct flex_array_part *)&fa->parts[0];

	else {

		part_nr = fa_element_to_part_nr(fa, element_nr);

		part = fa->parts[part_nr];

		if (!part)

			return -EINVAL;
@@ -264,6 +273,8 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start, 


	if (end >= fa->total_nr_elements)

		return -ENOSPC;

	if (!fa->element_size)

		return 0;

	if (elements_fit_in_base(fa))

		return 0;

	start_part = fa_element_to_part_nr(fa, start);
@@ -291,14 +302,17 @@ EXPORT_SYMBOL(flex_array_prealloc); 
 */

void *flex_array_get(struct flex_array *fa, unsigned int element_nr)

{

	int part_nr = fa_element_to_part_nr(fa, element_nr);

	int part_nr;

	struct flex_array_part *part;



	if (!fa->element_size)

		return NULL;

	if (element_nr >= fa->total_nr_elements)

		return NULL;

	if (elements_fit_in_base(fa))

		part = (struct flex_array_part *)&fa->parts[0];

	else {

		part_nr = fa_element_to_part_nr(fa, element_nr);

		part = fa->parts[part_nr];

		if (!part)

			return NULL;
@@ -353,7 +367,7 @@ int flex_array_shrink(struct flex_array *fa) 
	int part_nr;

	int ret = 0;



	if (!fa->total_nr_elements)

	if (!fa->total_nr_elements || !fa->element_size)

		return 0;

	if (elements_fit_in_base(fa))

		return ret;