linux-kernel - Re: [RFC PATCH 14/39] KVM: guest_memfd: hugetlb: initialization and cleanup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <diqz5xle9nwq.fsf@ackerleytng-ctop.c.googlers.com>
Date: Thu, 13 Feb 2025 09:47:33 +0000
From: Ackerley Tng <ackerleytng@...gle.com>
To: Peter Xu <peterx@...hat.com>
Cc: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk, 
	jgg@...dia.com, david@...hat.com, rientjes@...gle.com, fvdl@...gle.com, 
	jthoughton@...gle.com, seanjc@...gle.com, pbonzini@...hat.com, 
	zhiquan1.li@...el.com, fan.du@...el.com, jun.miao@...el.com, 
	isaku.yamahata@...el.com, muchun.song@...ux.dev, mike.kravetz@...cle.com, 
	erdemaktas@...gle.com, vannapurve@...gle.com, qperret@...gle.com, 
	jhubbard@...dia.com, willy@...radead.org, shuah@...nel.org, 
	brauner@...nel.org, bfoster@...hat.com, kent.overstreet@...ux.dev, 
	pvorel@...e.cz, rppt@...nel.org, richard.weiyang@...il.com, 
	anup@...infault.org, haibo1.xu@...el.com, ajones@...tanamicro.com, 
	vkuznets@...hat.com, maciej.wieczor-retman@...el.com, pgonda@...gle.com, 
	oliver.upton@...ux.dev, linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-fsdevel@...ck.org
Subject: Re: [RFC PATCH 14/39] KVM: guest_memfd: hugetlb: initialization and cleanup

Peter Xu <peterx@...hat.com> writes:

> On Tue, Sep 10, 2024 at 11:43:45PM +0000, Ackerley Tng wrote:
>> +/**
>> + * Removes folios in range [@lstart, @lend) from page cache of inode, updates
>> + * inode metadata and hugetlb reservations.
>> + */
>> +static void kvm_gmem_hugetlb_truncate_folios_range(struct inode *inode,
>> +						   loff_t lstart, loff_t lend)
>> +{
>> +	struct kvm_gmem_hugetlb *hgmem;
>> +	struct hstate *h;
>> +	int gbl_reserve;
>> +	int num_freed;
>> +
>> +	hgmem = kvm_gmem_hgmem(inode);
>> +	h = hgmem->h;
>> +
>> +	num_freed = kvm_gmem_hugetlb_filemap_remove_folios(inode->i_mapping,
>> +							   h, lstart, lend);
>> +
>> +	gbl_reserve = hugepage_subpool_put_pages(hgmem->spool, num_freed);
>> +	hugetlb_acct_memory(h, -gbl_reserve);
>
> I wonder whether this is needed, and whether hugetlb_acct_memory() needs to
> be exported in the other patch.
>
> IIUC subpools manages the global reservation on its own when min_pages is
> set (which should be gmem's case, where both max/min set to gmem size).
> That's in hugepage_put_subpool() -> unlock_or_release_subpool().
>

Thank you for pointing this out! You are right and I will remove
hugetlb_acct_memory() from here.

>> +
>> +	spin_lock(&inode->i_lock);
>> +	inode->i_blocks -= blocks_per_huge_page(h) * num_freed;
>> +	spin_unlock(&inode->i_lock);
>> +}