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Le 31/01/2019 à 07:44, Christophe Leroy a écrit :
>
>
> Le 31/01/2019 à 07:41, Mike Rapoport a écrit :
>> On Thu, Jan 31, 2019 at 07:07:46AM +0100, Christophe Leroy wrote:
>>>
>>>
>>> Le 21/01/2019 à 09:04, Mike Rapoport a écrit :
>>>> Add check for the return value of memblock_alloc*() functions and call
>>>> panic() in case of error.
>>>> The panic message repeats the one used by panicing memblock
>>>> allocators with
>>>> adjustment of parameters to include only relevant ones.
>>>>
>>>> The replacement was mostly automated with semantic patches like the one
>>>> below with manual massaging of format strings.
>>>>
>>>> @@
>>>> expression ptr, size, align;
>>>> @@
>>>> ptr = memblock_alloc(size, align);
>>>> + if (!ptr)
>>>> + panic("%s: Failed to allocate %lu bytes align=0x%lx\n", __func__,
>>>> size, align);
>>>>
>>>> Signed-off-by: Mike Rapoport <rppt****@linux*****>
>>>> Reviewed-by: Guo Ren <ren_guo****@c-sky*****> # c-sky
>>>> Acked-by: Paul Burton <paul.****@mips*****> # MIPS
>>>> Acked-by: Heiko Carstens <heiko****@de*****> # s390
>>>> Reviewed-by: Juergen Gross <jgros****@suse*****> # Xen
>>>> ---
>>>
>>> [...]
>>>
>>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>>> index 7ea5dc6..ad94242 100644
>>>> --- a/mm/sparse.c
>>>> +++ b/mm/sparse.c
>>>
>>> [...]
>>>
>>>> @@ -425,6 +436,10 @@ static void __init sparse_buffer_init(unsigned
>>>> long size, int nid)
>>>> memblock_alloc_try_nid_raw(size, PAGE_SIZE,
>>>> __pa(MAX_DMA_ADDRESS),
>>>> MEMBLOCK_ALLOC_ACCESSIBLE, nid);
>>>> + if (!sparsemap_buf)
>>>> + panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d
>>>> from=%lx\n",
>>>> + __func__, size, PAGE_SIZE, nid, __pa(MAX_DMA_ADDRESS));
>>>> +
>>>
>>> memblock_alloc_try_nid_raw() does not panic (help explicitly says:
>>> Does not
>>> zero allocated memory, does not panic if request cannot be satisfied.).
>>
>> "Does not panic" does not mean it always succeeds.
>
> I agree, but at least here you are changing the behaviour by making it
> panic explicitly. Are we sure there are not cases where the system could
> just continue functionning ? Maybe a WARN_ON() would be enough there ?
Looking more in details, it looks like everything is done to live with
sparsemap_buf NULL, all functions using it check it so having it NULL
shouldn't imply a panic I believe, see code below.
static void *sparsemap_buf __meminitdata;
static void *sparsemap_buf_end __meminitdata;
static void __init sparse_buffer_init(unsigned long size, int nid)
{
WARN_ON(sparsemap_buf); /* forgot to call sparse_buffer_fini()? */
sparsemap_buf =
memblock_alloc_try_nid_raw(size, PAGE_SIZE,
__pa(MAX_DMA_ADDRESS),
MEMBLOCK_ALLOC_ACCESSIBLE, nid);
sparsemap_buf_end = sparsemap_buf + size;
}
static void __init sparse_buffer_fini(void)
{
unsigned long size = sparsemap_buf_end - sparsemap_buf;
if (sparsemap_buf && size > 0)
memblock_free_early(__pa(sparsemap_buf), size);
sparsemap_buf = NULL;
}
void * __meminit sparse_buffer_alloc(unsigned long size)
{
void *ptr = NULL;
if (sparsemap_buf) {
ptr = PTR_ALIGN(sparsemap_buf, size);
if (ptr + size > sparsemap_buf_end)
ptr = NULL;
else
sparsemap_buf = ptr + size;
}
return ptr;
}
Christophe