On Tue, Jan 08, 2019 at 05:01:38PM +0800, Baoquan He wrote: > Hi Mike, > > On 01/08/19 at 10:05am, Mike Rapoport wrote: > > I'm not thrilled by duplicating this code (yet again). > > I liked the v3 of this patch [1] more, assuming we allow bottom-up mode to > > allocate [0, kernel_start) unconditionally. > > I'd just replace you first patch in v3 [2] with something like: > > In initmem_init(), we will restore the top-down allocation style anyway. > While reserve_crashkernel() is called after initmem_init(), it's not > appropriate to adjust memblock_find_in_range_node(), and we really want > to find region bottom up for crashkernel reservation, no matter where > kernel is loaded, better call __memblock_find_range_bottom_up(). > > Create a wrapper to do the necessary handling, then call > __memblock_find_range_bottom_up() directly, looks better.
What bothers me is 'the necessary handling' which is already done in several places in memblock in a similar, but yet slightly different way. memblock_find_in_range() and memblock_phys_alloc_nid() retry with different MEMBLOCK_MIRROR, but memblock_phys_alloc_try_nid() does that only when allocating from the specified node and does not retry when it falls back to any node. And memblock_alloc_internal() has yet another set of fallbacks. So what should be the necessary handling in the wrapper for __memblock_find_range_bottom_up() ? BTW, even without any memblock modifications, retrying allocation in reserve_crashkerenel() for different ranges, like the proposal at [1] would also work, wouldn't it? [1] http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > Thanks > Baoquan > > > > > diff --git a/mm/memblock.c b/mm/memblock.c > > index 7df468c..d1b30b9 100644 > > --- a/mm/memblock.c > > +++ b/mm/memblock.c > > @@ -274,24 +274,14 @@ phys_addr_t __init_memblock > > memblock_find_in_range_node(phys_addr_t size, > > * try bottom-up allocation only when bottom-up mode > > * is set and @end is above the kernel image. > > */ > > - if (memblock_bottom_up() && end > kernel_end) { > > - phys_addr_t bottom_up_start; > > - > > - /* make sure we will allocate above the kernel */ > > - bottom_up_start = max(start, kernel_end); > > - > > + if (memblock_bottom_up()) { > > /* ok, try bottom-up allocation first */ > > - ret = __memblock_find_range_bottom_up(bottom_up_start, end, > > + ret = __memblock_find_range_bottom_up(start, end, > > size, align, nid, flags); > > if (ret) > > return ret; > > > > /* > > - * we always limit bottom-up allocation above the kernel, > > - * but top-down allocation doesn't have the limit, so > > - * retrying top-down allocation may succeed when bottom-up > > - * allocation failed. > > - * > > * bottom-up allocation is expected to be fail very rarely, > > * so we use WARN_ONCE() here to see the stack trace if > > * fail happens. > > > > [1] > > https://lore.kernel.org/lkml/1545966002-3075-3-git-send-email-kernelf...@gmail.com/ > > [2] > > https://lore.kernel.org/lkml/1545966002-3075-2-git-send-email-kernelf...@gmail.com/ > > > > > + > > > + return ret; > > > +} > > > + > > > /** > > > * __memblock_find_range_top_down - find free area utility, in top-down > > > * @start: start of candidate range > > > -- > > > 2.7.4 > > > > > > > -- > > Sincerely yours, > > Mike. > > > -- Sincerely yours, Mike.
