From: "Michal Nazarewicz" <mina86@mina86.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
linux-mm@kvack.org, Kyungmin Park <kyungmin.park@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Ankita Garg <ankita@in.ibm.com>,
Daniel Walker <dwalker@codeaurora.org>,
Johan MOSSBERG <johan.xx.mossberg@stericsson.com>,
Mel Gorman <mel@csn.ul.ie>, Pawel Osciak <pawel@osciak.com>
Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added
Date: Fri, 01 Apr 2011 00:51:32 +0200 [thread overview]
Message-ID: <op.vs8cf5xd3l0zgt@mnazarewicz-glaptop> (raw)
In-Reply-To: <1301610411.30870.29.camel@nimitz>
On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@linux.vnet.ibm.com>
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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next prev parent reply other threads:[~2011-03-31 22:51 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-31 13:15 [PATCHv9 0/12] Contiguous Memory Allocator Marek Szyprowski
2011-03-31 13:15 ` [PATCH 01/12] lib: bitmap: Added alignment offset for bitmap_find_next_zero_area() Marek Szyprowski
2011-03-31 13:15 ` [PATCH 02/12] lib: genalloc: Generic allocator improvements Marek Szyprowski
2011-03-31 13:15 ` [PATCH 03/12] mm: move some functions from memory_hotplug.c to page_isolation.c Marek Szyprowski
2011-03-31 13:16 ` [PATCH 04/12] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-03-31 15:58 ` Dave Hansen
2011-03-31 19:24 ` Steven Rostedt
2011-03-31 20:33 ` Dave Hansen
2011-03-31 21:09 ` Michal Nazarewicz
2011-03-31 21:14 ` Dave Hansen
2011-03-31 22:18 ` Michal Nazarewicz
2011-03-31 22:26 ` Dave Hansen
2011-03-31 22:51 ` Michal Nazarewicz [this message]
2011-04-01 14:03 ` Dave Hansen
2011-04-04 13:15 ` Michal Nazarewicz
2011-04-05 7:23 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 05/12] mm: alloc_contig_range() added Marek Szyprowski
2011-03-31 16:02 ` Dave Hansen
2011-03-31 16:26 ` Michal Nazarewicz
2011-03-31 19:28 ` Steven Rostedt
2011-03-31 19:52 ` Michal Nazarewicz
2011-03-31 20:28 ` Dave Hansen
2011-03-31 21:17 ` Michal Nazarewicz
2011-03-31 19:26 ` Steven Rostedt
2011-03-31 16:04 ` Dave Hansen
2011-03-31 13:16 ` [PATCH 06/12] mm: cma: Contiguous Memory Allocator added Marek Szyprowski
2011-03-31 13:16 ` [PATCH 07/12] mm: MIGRATE_CMA migration type added Marek Szyprowski
2011-03-31 13:16 ` [PATCH 08/12] mm: MIGRATE_CMA isolation functions added Marek Szyprowski
2011-03-31 13:16 ` [PATCH 09/12] mm: MIGRATE_CMA support added to CMA Marek Szyprowski
2011-03-31 13:16 ` [PATCH 10/12] mm: cma: add CMA 'regions style' API (for testing) Marek Szyprowski
2011-03-31 13:16 ` [PATCH 11/12] v4l: videobuf2: add CMA allocator " Marek Szyprowski
2011-03-31 13:16 ` [PATCH 12/12] ARM: S5PC110: Added CMA regions to Aquila and Goni boards Marek Szyprowski
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