linux-kernel - Re: [PATCH 2/8] mm/memory_hotplug: fix error handling in add_memory

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Message-ID: <ZVTLc+rcMVt17AKL@li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com>
Date:   Wed, 15 Nov 2023 14:45:23 +0100
From:   Sumanth Korikkar <sumanthk@...ux.ibm.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Vishal Verma <vishal.l.verma@...el.com>
Subject: Re: [PATCH 2/8] mm/memory_hotplug: fix error handling in
 add_memory_resource()

On Tue, Nov 14, 2023 at 07:36:20PM +0100, David Hildenbrand wrote:
> On 14.11.23 19:02, Sumanth Korikkar wrote:
> > In add_memory_resource(), creation of memory block devices occurs after
> > successful call to arch_add_memory(). However, creation of memory block
> > devices could fail.  In that case, arch_remove_memory() is called to
> > perform necessary cleanup.
> > 
> > Currently with or without altmap support, arch_remove_memory() is always
> > passed with altmap set to NULL during error handling. This leads to
> > freeing of struct pages using free_pages(), eventhough the allocation
> > might have been performed with altmap support via
> > altmap_alloc_block_buf().
> > 
> > Fix the error handling by passing altmap in arch_remove_memory(). This
> > ensures the following:
> > * When altmap is disabled, deallocation of the struct pages array occurs
> >    via free_pages().
> > * When altmap is enabled, deallocation occurs via vmem_altmap_free().
> > 
> > Fixes: db051a0dac13 ("mm/memory_hotplug: create memory block devices after arch_add_memory()")
> 
> That's the wrong commit. We didn't support memmap-on-memory back then.
> 
> Likely it should be:
> 
> Fixes: a08a2ae34613 ("mm,memory_hotplug: allocate memmap from the added
> memory range")
>
Ok, I will change it accordingly

Thanks
...
> 
> Indeed; this will conflict with Vishals patches, ccing him.
> 
> -- 
> Cheers,
> 
> David / dhildenb
>