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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2018-02-22 01:45:43 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-22 02:35:43 +0300
commitb1a8a7a70043400d1e685899548c92b92f640d71 (patch)
tree4295e3cb0440b43ad6a2b95a777b4bccb858bdb6 /lib/idr.c
parent7ba716698cc53f8d5367766c93c538c7da6c68ce (diff)
downloadlinux-b1a8a7a70043400d1e685899548c92b92f640d71.tar.xz
ida: do zeroing in ida_pre_get()
As far as I can tell, the only place the per-cpu ida_bitmap is populated is in ida_pre_get. The pre-allocated element is stolen in two places in ida_get_new_above, in both cases immediately followed by a memset(0). Since ida_get_new_above is called with locks held, do the zeroing in ida_pre_get, or rather let kmalloc() do it. Also, apparently gcc generates ~44 bytes of code to do a memset(, 0, 128): $ scripts/bloat-o-meter vmlinux.{0,1} add/remove: 0/0 grow/shrink: 2/1 up/down: 5/-88 (-83) Function old new delta ida_pre_get 115 119 +4 vermagic 27 28 +1 ida_get_new_above 715 627 -88 Link: http://lkml.kernel.org/r/20180108225634.15340-1-linux@rasmusvillemoes.dk Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Acked-by: Matthew Wilcox <mawilcox@microsoft.com> Cc: Eric Biggers <ebiggers@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/idr.c')
-rw-r--r--lib/idr.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/lib/idr.c b/lib/idr.c
index c98d77fcf393..99ec5bc89d25 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -431,7 +431,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
rcu_assign_pointer(*slot, bitmap);
}
@@ -464,7 +463,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
__set_bit(bit, bitmap->bitmap);
radix_tree_iter_replace(root, &iter, slot, bitmap);
}