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percpu: do not search past bitmap when allocating an area

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pcpu_find_block_fit() guarantees that a fit is found within
PCPU_BITMAP_BLOCK_BITS. Iteration is used to determine the first fit as
it compares against the block's contig_hint. This can lead to
incorrectly scanning past the end of the bitmap. The behavior was okay
given the check after for bit_off >= end and the correctness of the
hints from pcpu_find_block_fit().

This patch fixes this by bounding the end offset by the number of bits
in a chunk.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
This commit is contained in:
Dennis Zhou 2019-02-21 15:54:11 -08:00
parent 8e5a2b9893
commit 8c43004af0
1 changed files with 2 additions and 1 deletions
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3
mm/percpu.c
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@ -988,7 +988,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
/*
* Search to find a fit.
*/
end = start + alloc_bits + PCPU_BITMAP_BLOCK_BITS;
end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
pcpu_chunk_map_bits(chunk));
bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
alloc_bits, align_mask);
if (bit_off >= end)