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| author | Daniel Mentz <danielmentz@google.com> | 2016-10-28 03:46:59 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-28 04:43:43 +0300 |
| commit | 62e931fac45b17c2a42549389879411572f75804 (patch) | |
| tree | a66bc11e84beee712de9fd2d4711d722db0edd80 /lib/genalloc.c | |
| parent | 89a2848381b5fcd9c4d9c0cd97680e3b28730e31 (diff) | |
| download | linux-62e931fac45b17c2a42549389879411572f75804.tar.xz | |
lib/genalloc.c: start search from start of chunk
gen_pool_alloc_algo() iterates over the chunks of a pool trying to find
a contiguous block of memory that satisfies the allocation request.
The shortcut
if (size > atomic_read(&chunk->avail))
continue;
makes the loop skip over chunks that do not have enough bytes left to
fulfill the request. There are two situations, though, where an
allocation might still fail:
(1) The available memory is not contiguous, i.e. the request cannot
be fulfilled due to external fragmentation.
(2) A race condition. Another thread runs the same code concurrently
and is quicker to grab the available memory.
In those situations, the loop calls pool->algo() to search the entire
chunk, and pool->algo() returns some value that is >= end_bit to
indicate that the search failed. This return value is then assigned to
start_bit. The variables start_bit and end_bit describe the range that
should be searched, and this range should be reset for every chunk that
is searched. Today, the code fails to reset start_bit to 0. As a
result, prefixes of subsequent chunks are ignored. Memory allocations
might fail even though there is plenty of room left in these prefixes of
those other chunks.
Fixes: 7f184275aa30 ("lib, Make gen_pool memory allocator lockless")
Link: http://lkml.kernel.org/r/1477420604-28918-1-git-send-email-danielmentz@google.com
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/genalloc.c')
| -rw-r--r-- | lib/genalloc.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/genalloc.c b/lib/genalloc.c index 0a1139644d32..144fe6b1a03e 100644 --- a/lib/genalloc.c +++ b/lib/genalloc.c @@ -292,7 +292,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size, struct gen_pool_chunk *chunk; unsigned long addr = 0; int order = pool->min_alloc_order; - int nbits, start_bit = 0, end_bit, remain; + int nbits, start_bit, end_bit, remain; #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG BUG_ON(in_nmi()); @@ -307,6 +307,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size, if (size > atomic_read(&chunk->avail)) continue; + start_bit = 0; end_bit = chunk_size(chunk) >> order; retry: start_bit = algo(chunk->bits, end_bit, start_bit, |