linux-kernel - Re: [PATCH v2 1/3] mm: fixup pfnmap memory failure handling to use pgoff

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Message-ID:
 <SA1PR12MB7199065CD785B5FD0BFE6FB9B0ABA@SA1PR12MB7199.namprd12.prod.outlook.com>
Date: Wed, 17 Dec 2025 18:10:34 +0000
From: Ankit Agrawal <ankita@...dia.com>
To: Miaohe Lin <linmiaohe@...wei.com>
CC: Neo Jia <cjia@...dia.com>, Zhi Wang <zhiw@...dia.com>, Krishnakant Jaju
	<kjaju@...dia.com>, Yishai Hadas <yishaih@...dia.com>, "kevin.tian@...el.com"
	<kevin.tian@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, Vikram Sethi <vsethi@...dia.com>,
	Jason Gunthorpe <jgg@...dia.com>, Matt Ochs <mochs@...dia.com>,
	"jgg@...pe.ca" <jgg@...pe.ca>, Shameer Kolothum <skolothumtho@...dia.com>,
	"alex@...zbot.org" <alex@...zbot.org>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "nao.horiguchi@...il.com"
	<nao.horiguchi@...il.com>
Subject: Re: [PATCH v2 1/3] mm: fixup pfnmap memory failure handling to use
 pgoff

>>       i_mmap_lock_read(mapping);
>>       rcu_read_lock();
>> @@ -2226,9 +2230,12 @@ static void collect_procs_pfn(struct address_space *mapping,
>>               t = task_early_kill(tsk, true);
>>               if (!t)
>>                       continue;
>> -             vma_interval_tree_foreach(vma, &mapping->i_mmap, pfn, pfn) {
>> -                     if (vma->vm_mm == t->mm)
>> -                             add_to_kill_pfn(t, vma, to_kill, pfn);
>> +             vma_interval_tree_foreach(vma, &mapping->i_mmap, 0, ULONG_MAX) {
>> +                     pgoff_t pgoff;
>
> IIUC, all vma will be traversed to find the final pgoff. This might not be a good idea
> because rcu lock is held and this traversal might take a really long time. Or am I miss
> something?

Hi Miaohe, the VMAs on the registered address space will be checked. For the nvgrace-gpu
user of this API in 3/3, there are only 3 VMAs on the registered address space (that are
associated with the vfio file).