On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
wrote:
On Fri, 2011-04-01 at 00:18 +0200, Michal Nazarewicz wrote:
On Thu, 31 Mar 2011 23:14:38 +0200, Dave Hansen wrote:
> We BUG_ON() in bootmem. Basically if we try to allocate an early-boot
> structure and fail, we're screwed. We can't keep running without an
> inode hash, or a mem_map[].
>
> This looks like it's going to at least get partially used in drivers,
at
> least from the examples. Are these kinds of things that, if the
driver
> fails to load, that the system is useless and hosed? Or, is it
> something where we might limp along to figure out what went wrong
before
> we reboot?
Bug in the above place does not mean that we could not allocate
memory. It means caller is broken.
Could you explain that a bit?
Is this a case where a device is mapped to a very *specific* range of
physical memory and no where else? What are the reasons for not marking
it off limits at boot? I also saw some bits of isolation and migration
in those patches. Can't the migration fail?
The function is called from alloc_contig_range() (see patch 05/12) which
makes sure that the PFN is valid. Situation where there is not enough
space is caught earlier in alloc_contig_range().
alloc_contig_freed_pages() must be given a valid PFN range such that all
the pages in that range are free (as in are within the region tracked by
page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't
touch them.
That's why invalid PFN is a bug in the caller and not an exception that
has to be handled.
Also, the function is not called during boot time. It is called while
system is already running.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
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