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>
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@ -431,7 +431,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
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bitmap = this_cpu_xchg(ida_bitmap, NULL);
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if (!bitmap)
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return -EAGAIN;
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memset(bitmap, 0, sizeof(*bitmap));
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bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
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rcu_assign_pointer(*slot, bitmap);
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}
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@ -464,7 +463,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
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bitmap = this_cpu_xchg(ida_bitmap, NULL);
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if (!bitmap)
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return -EAGAIN;
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memset(bitmap, 0, sizeof(*bitmap));
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__set_bit(bit, bitmap->bitmap);
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radix_tree_iter_replace(root, &iter, slot, bitmap);
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}
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@ -2125,7 +2125,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
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preempt_enable();
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if (!this_cpu_read(ida_bitmap)) {
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struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
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struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp);
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if (!bitmap)
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return 0;
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if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
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