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Subject[PATCHv2 net 2/3] flex_array: support flex_array_resize
Date
This function can dynamically change total_nr_elements of a flex_array,
and keep the old elements of the same memory. Returns 0 if it succeeds.

Note that it won't do any memory allocation or shrinking for elements,
which should be only done by flex_array_prealloc and flex_array_shrink.

Suggested-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
---
include/linux/flex_array.h | 11 +++++++++
lib/flex_array.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+)

diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
index 29ad65f..19ff58d 100644
--- a/include/linux/flex_array.h
+++ b/include/linux/flex_array.h
@@ -130,6 +130,17 @@ void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
*/
int flex_array_shrink(struct flex_array *fa);

+/**
+ * flex_array_resize() - Resize without the old elements memory changed
+ * @fa: array to resize
+ * @total: total number of elements that this would change to
+ * @flags: page allocation flags to use for base array
+ *
+ * Return: Returns 0 if it succeeds.
+ *
+ */
+int flex_array_resize(struct flex_array *fa, unsigned int total, gfp_t flags);
+
#define flex_array_put_ptr(fa, nr, src, gfp) \
flex_array_put(fa, nr, (void *)&(src), gfp)

diff --git a/lib/flex_array.c b/lib/flex_array.c
index 8c0b9b6..2f913e7 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -405,3 +405,61 @@ int flex_array_shrink(struct flex_array *fa)
return ret;
}
EXPORT_SYMBOL(flex_array_shrink);
+
+/**
+ * flex_array_resize - resize without the old elements memory changed
+ * @fa: the flex array to resize
+ * @total: total number of elements that this would change to
+ * @flags: page allocation flags to use for base array
+ *
+ * This function can dynamically change total_nr_elements of a flex_array,
+ * and keep the old elements of the same memory. Returns 0 if it succeeds.
+ * Note that it won't do any memory allocation or shrinking for elements,
+ * which should be only done by flex_array_prealloc and flex_array_shrink.
+ *
+ * Locking must be provided by the caller.
+ */
+int flex_array_resize(struct flex_array *fa, unsigned int total, gfp_t flags)
+{
+ int nr;
+
+ if (total > FLEX_ARRAY_NR_BASE_PTRS * fa->elems_per_part)
+ return -EINVAL;
+
+ if (elements_fit_in_base(fa)) {
+ struct flex_array_part_p *part_p;
+
+ nr = fa->total_nr_elements;
+ fa->total_nr_elements = total;
+ if (elements_fit_in_base(fa))
+ return 0;
+
+ part_p = kzalloc(sizeof(*part_p), flags);
+ if (!part_p) {
+ fa->total_nr_elements = nr;
+ return -ENOMEM;
+ }
+
+ part_p->p_part[0] = (struct flex_array_part *)&fa->parts[0];
+ fa->part_p = part_p;
+ } else {
+ struct flex_array_part *part;
+
+ fa->total_nr_elements = total;
+ if (!elements_fit_in_base(fa))
+ return 0;
+
+ for (nr = 1; nr < FLEX_ARRAY_NR_BASE_PTRS; nr++) {
+ part = fa->parts[nr];
+ if (part) {
+ fa->parts[nr] = NULL;
+ kfree(part);
+ }
+ }
+
+ fa->part_p = (struct flex_array_part_p *)fa->parts[0];
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(flex_array_resize);
--
2.1.0
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