linux-kernel - Re: [PATCH v2 1/6] mm/huge_memory: add two new (yet used) functions for folio

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Message-ID: <7C0C7025-DBCF-4544-8E95-1E781CA94710@nvidia.com>
Date: Thu, 07 Nov 2024 10:01:11 -0500
From: Zi Yan <ziy@...dia.com>
To: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: linux-mm@...ck.org, Ryan Roberts <ryan.roberts@....com>,
 Hugh Dickins <hughd@...gle.com>, David Hildenbrand <david@...hat.com>,
 Yang Shi <yang@...amperecomputing.com>, Miaohe Lin <linmiaohe@...wei.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Yu Zhao <yuzhao@...gle.com>,
 John Hubbard <jhubbard@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] mm/huge_memory: add two new (yet used) functions
 for folio_split()

>>
>>> +
>>> +		if (mapping) {
>>> +			/*
>>> +			 * uniform split has xas_split_alloc() called before
>>> +			 * irq is disabled, since xas_nomem() might not be
>>> +			 * able to allocate enough memory.
>>> +			 */
>>> +			if (uniform_split)
>>> +				xas_split(xas, folio, old_order);
>>> +			else {
>>> +				xas_set_order(xas, folio->index, split_order);
>>> +				xas_set_err(xas, -ENOMEM);
>>> +				if (xas_nomem(xas, 0))
>>
>> 0 gfp?
>
> This is inside lru_lock and allocation cannot sleep, so I am not sure
> current_gfp_context(mapping_gfp_mask(mapping) &	GFP_RECLAIM_MASK); can
> be used.
>
> I need Matthew to help me out about this.

Talked to Matthew about this, will use GFP_NOWAIT here, since we can fail
here and probably should not get into atomic reserves.

Best Regards,
Yan, Zi