From 4af5a2f770cc8575840ccb1514ec76ecb592985c Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Mon, 21 Sep 2009 17:04:31 -0700 Subject: [PATCH] flex_array: add flex_array_shrink function Add a new function to the flex_array API: int flex_array_shrink(struct flex_array *fa) This function will free all unused second-level pages. Since elements are now poisoned if they are not allocated with __GFP_ZERO, it's possible to identify parts that consist solely of unused elements. flex_array_shrink() returns the number of pages freed. Signed-off-by: David Rientjes Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/flex_array.h | 1 + lib/flex_array.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h index 3887b21..f12401e 100644 --- a/include/linux/flex_array.h +++ b/include/linux/flex_array.h @@ -46,5 +46,6 @@ int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src, gfp_t flags); int flex_array_clear(struct flex_array *fa, unsigned int element_nr); void *flex_array_get(struct flex_array *fa, unsigned int element_nr); +int flex_array_shrink(struct flex_array *fa); #endif /* _FLEX_ARRAY_H */ diff --git a/lib/flex_array.c b/lib/flex_array.c index e22d0e9..1b03bb5 100644 --- a/lib/flex_array.c +++ b/lib/flex_array.c @@ -291,3 +291,43 @@ void *flex_array_get(struct flex_array *fa, unsigned int element_nr) } return &part->elements[index_inside_part(fa, element_nr)]; } + +static int part_is_free(struct flex_array_part *part) +{ + int i; + + for (i = 0; i < sizeof(struct flex_array_part); i++) + if (part->elements[i] != FLEX_ARRAY_FREE) + return 0; + return 1; +} + +/** + * flex_array_shrink - free unused second-level pages + * + * Frees all second-level pages that consist solely of unused + * elements. Returns the number of pages freed. + * + * Locking must be provided by the caller. + */ +int flex_array_shrink(struct flex_array *fa) +{ + struct flex_array_part *part; + int max_part = nr_base_part_ptrs(); + int part_nr; + int ret = 0; + + if (elements_fit_in_base(fa)) + return ret; + for (part_nr = 0; part_nr < max_part; part_nr++) { + part = fa->parts[part_nr]; + if (!part) + continue; + if (part_is_free(part)) { + fa->parts[part_nr] = NULL; + kfree(part); + ret++; + } + } + return ret; +} -- 2.7.4