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Date: Tue, 12 Feb 2008 09:22:32 -0800
From: Badari Pulavarty <pbadari@...ibm.com>
To: Yasunori Goto <y-goto@...fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
lkml <linux-kernel@...r.kernel.org>, greg@...ah.com,
haveblue@...ibm.com, linux-mm <linux-mm@...ck.org>
Subject: Re: [-mm PATCH] register_memory/unregister_memory clean ups
On Tue, 2008-02-12 at 17:06 +0900, Yasunori Goto wrote:
> > On Mon, 2008-02-11 at 11:48 -0800, Andrew Morton wrote:
> > > On Mon, 11 Feb 2008 09:23:18 -0800
> > > Badari Pulavarty <pbadari@...ibm.com> wrote:
> > >
> > > > Hi Andrew,
> > > >
> > > > While testing hotplug memory remove against -mm, I noticed
> > > > that unregister_memory() is not cleaning up /sysfs entries
> > > > correctly. It also de-references structures after destroying
> > > > them (luckily in the code which never gets used). So, I cleaned
> > > > up the code and fixed the extra reference issue.
> > > >
> > > > Could you please include it in -mm ?
> > > >
> > > > Thanks,
> > > > Badari
> > > >
> > > > register_memory()/unregister_memory() never gets called with
> > > > "root". unregister_memory() is accessing kobject_name of
> > > > the object just freed up. Since no one uses the code,
> > > > lets take the code out. And also, make register_memory() static.
> > > >
> > > > Another bug fix - before calling unregister_memory()
> > > > remove_memory_block() gets a ref on kobject. unregister_memory()
> > > > need to drop that ref before calling sysdev_unregister().
> > > >
> > >
> > > I'd say this:
> > >
> > > > Subject: [-mm PATCH] register_memory/unregister_memory clean ups
> > >
> > > is rather tame. These are more than cleanups! These sound like
> > > machine-crashing bugs. Do they crash machines? How come nobody noticed
> > > it?
> > >
> >
> > No they don't crash machine - mainly because, they never get called
> > with "root" argument (where we have the bug). They were never tested
> > before, since we don't have memory remove work yet. All it does
> > is, it leave /sysfs directory laying around and causing next
> > memory add failure.
>
> Badari-san.
>
> Which function does call unregister_memory() or unregister_memory_section()?
> I can't find its caller in current 2.6.24-mm1.
>
>
> ???????()
> |
> |nothing calls?
> |
> +-->unregister_memory_section()
> |
> |call
> |
> +---> remove_memory_block()
> |
> |call
> |
> +----> unregister_memory()
>
> unregister_memory_section() is only externed in linux/memory.h.
>
> Do you have any another patch to call it?
> I think it is necessary for physical memory removing.
>
> If you have not posted it or it is not merged to -mm,
> I can understand why this bug remains.
> If you posted it, could you point it to me?
Yes. I am trying to complete the hotplug memory remove
support, so that I can use it for supporting it on ppc64
DLPAR environment.
Here is the patch to finish up some of the generic work
left. As you can see, I still need to finish up some work :(
Any help is appreciated :)
Thanks,
Badari
---
include/linux/memory_hotplug.h | 4 ++++
mm/memory_hotplug.c | 33 +++++++++++++++++++++++++++++++++
mm/sparse.c | 40 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 77 insertions(+)
Index: linux-2.6.24/mm/memory_hotplug.c
===================================================================
--- linux-2.6.24.orig/mm/memory_hotplug.c 2008-02-07 17:16:52.000000000 -0800
+++ linux-2.6.24/mm/memory_hotplug.c 2008-02-07 17:17:57.000000000 -0800
@@ -81,6 +81,14 @@ static int __add_zone(struct zone *zone,
return 0;
}
+static void __remove_zone(struct zone *zone, unsigned long phys_start_pfn)
+{
+ /*
+ * TODO - Check to see if the zone is correctly adjusted
+ * Need to mark pages reserved ?
+ */
+}
+
static int __add_section(struct zone *zone, unsigned long phys_start_pfn)
{
int nr_pages = PAGES_PER_SECTION;
@@ -102,6 +110,16 @@ static int __add_section(struct zone *zo
return register_new_memory(__pfn_to_section(phys_start_pfn));
}
+static void __remove_section(struct zone *zone, unsigned long phys_start_pfn)
+{
+ if (!pfn_valid(phys_start_pfn))
+ return;
+
+ unregister_memory_section(__pfn_to_section(phys_start_pfn));
+ __remove_zone(zone, phys_start_pfn);
+ sparse_remove_one_section(zone, phys_start_pfn, PAGES_PER_SECTION);
+}
+
/*
* Reasonably generic function for adding memory. It is
* expected that archs that support memory hotplug will
@@ -135,6 +153,21 @@ int __add_pages(struct zone *zone, unsig
}
EXPORT_SYMBOL_GPL(__add_pages);
+void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
+ unsigned long nr_pages)
+{
+ unsigned long i;
+ int start_sec, end_sec;
+
+ start_sec = pfn_to_section_nr(phys_start_pfn);
+ end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
+
+ for (i = start_sec; i <= end_sec; i++)
+ __remove_section(zone, i << PFN_SECTION_SHIFT);
+
+}
+EXPORT_SYMBOL_GPL(__remove_pages);
+
static void grow_zone_span(struct zone *zone,
unsigned long start_pfn, unsigned long end_pfn)
{
Index: linux-2.6.24/mm/sparse.c
===================================================================
--- linux-2.6.24.orig/mm/sparse.c 2008-02-07 17:16:52.000000000 -0800
+++ linux-2.6.24/mm/sparse.c 2008-02-11 14:12:28.000000000 -0800
@@ -415,4 +415,44 @@ out:
}
return ret;
}
+
+void sparse_remove_one_section(struct zone *zone, unsigned long start_pfn,
+ int nr_pages)
+{
+ unsigned long section_nr = pfn_to_section_nr(start_pfn);
+ struct pglist_data *pgdat = zone->zone_pgdat;
+ struct mem_section *ms;
+ struct page *memmap = NULL;
+ unsigned long *usemap = NULL;
+ unsigned long flags;
+
+ pgdat_resize_lock(pgdat, &flags);
+ ms = __pfn_to_section(start_pfn);
+ if (ms->section_mem_map) {
+ memmap = ms->section_mem_map & SECTION_MAP_MASK;
+ usemap = ms->pageblock_flags;
+ memmap = sparse_decode_mem_map((unsigned long)memmap,
+ section_nr);
+ ms->section_mem_map = 0;
+ ms->pageblock_flags = NULL;
+ }
+ pgdat_resize_unlock(pgdat, &flags);
+
+ /*
+ * Its ugly, but this is the best I can do - HELP !!
+ * We don't know where the allocations for section memmap and usemap
+ * came from. If they are allocated at the boot time, they would come
+ * from bootmem. If they are added through hot-memory-add they could be
+ * from sla or vmalloc. If they are allocated as part of hot-mem-add
+ * free them up properly. If they are allocated at boot, no easy way
+ * to correctly free them :(
+ */
+ if (usemap) {
+ if (PageSlab(virt_to_page(usemap))) {
+ kfree(usemap);
+ if (memmap)
+ __kfree_section_memmap(memmap, nr_pages);
+ }
+ }
+}
#endif
Index: linux-2.6.24/include/linux/memory_hotplug.h
===================================================================
--- linux-2.6.24.orig/include/linux/memory_hotplug.h 2008-02-07 17:16:52.000000000 -0800
+++ linux-2.6.24/include/linux/memory_hotplug.h 2008-02-07 17:17:57.000000000 -0800
@@ -64,6 +64,8 @@ extern int offline_pages(unsigned long,
/* reasonably generic interface to expand the physical pages in a zone */
extern int __add_pages(struct zone *zone, unsigned long start_pfn,
unsigned long nr_pages);
+extern void __remove_pages(struct zone *zone, unsigned long start_pfn,
+ unsigned long nr_pages);
/*
* Walk thorugh all memory which is registered as resource.
@@ -188,5 +190,7 @@ extern int arch_add_memory(int nid, u64
extern int remove_memory(u64 start, u64 size);
extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
int nr_pages);
+extern void sparse_remove_one_section(struct zone *zone,
+ unsigned long start_pfn, int nr_pages);
#endif /* __LINUX_MEMORY_HOTPLUG_H */
--
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