From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 248391CA88 for ; Mon, 5 Feb 2024 12:38:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707136731; cv=none; b=p7r+f0LkPccDKq/NJvwc76R6T4nrOCjOjGSSGsperG1slO5URGCH+/qZZiPHwO6AijJdkw5oTElw/QRnKJ2nEMfNxD4uAbOfmnumvJCx/2x75zp/bFAkLiOxeuMqtvz2eA3znzuM1rUqB8dt0xmMtoRtGZaObrj5EV4Jr9C84oo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707136731; c=relaxed/simple; bh=WPGXq2rV+SqQbpUMqD9YNjZ2jjtUSAl3Nfvhhth2sE8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F6nVUFA039ej6zDPTDkbwPFBOm/qKyxgkce1aY38X92g5258Nwt18faHFObIeUyLnchZd0+WfjAYeM1IOeuthKXwbn/YGAUZGjkdUsSPs9JBiGIdF8Yq9+0s1mBoipyhvOYC2q5302xfmEKqHcqSvR239ZMbmhon33iVnnYfLUY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=C/Mso+Ar; arc=none smtp.client-ip=115.124.30.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="C/Mso+Ar" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1707136720; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=EPrTp2HaSci14lwoV1Q3t2am9bD2lGmQe7hOOG3fJgk=; b=C/Mso+Ar5rA3ddRqyakX7X+iNkgtpf0PIjXj/NlCAqPc3bZwxFgA5dZFPjVPHNuqM2B23cL9mQud2XYkVzLE79uxUcnHEjLEHlw+Bq9pYbwbaYtSpjwpHf0oF5zne2Blcbv7Rrv1XneXeeou7o/gMtn6ozs09wuA5+J8LZIyw30= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R981e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0W0AY-Un_1707136718; Received: from 192.168.0.105(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0W0AY-Un_1707136718) by smtp.aliyun-inc.com; Mon, 05 Feb 2024 20:38:39 +0800 Message-ID: <88ff7f59-654c-4313-b2db-a926b4ca86b9@linux.alibaba.com> Date: Mon, 5 Feb 2024 20:38:53 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: hugetlb: fix hugetlb allocation failure when handling freed or in-use hugetlb To: Michal Hocko Cc: akpm@linux-foundation.org, muchun.song@linux.dev, osalvador@suse.de, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/5/2024 5:31 PM, Michal Hocko wrote: > On Mon 05-02-24 11:54:17, Baolin Wang wrote: >> When handling the freed hugetlb or in-use hugetlb, we should ignore the >> failure of alloc_buddy_hugetlb_folio() to dissolve the old hugetlb successfully, >> since we did not use the new allocated hugetlb in this 2 cases. >> >> Signed-off-by: Baolin Wang >> --- >> mm/hugetlb.c | 18 ++++++++++++------ >> 1 file changed, 12 insertions(+), 6 deletions(-) >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 9d996fe4ecd9..212ab331d355 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -3042,9 +3042,8 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h, >> * under the lock. >> */ >> new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL); >> - if (!new_folio) >> - return -ENOMEM; >> - __prep_new_hugetlb_folio(h, new_folio); >> + if (new_folio) >> + __prep_new_hugetlb_folio(h, new_folio); > > Is there any reason why you haven't moved the allocation to the only > branch that actually needs it? I know that we hold hugetlb lock but you Nope, just did a simple patch to ignore the allocation failure. > could have easily dropped the lock, allocate a page and then goto retry. > This would actually save an allocation. Yes, will do. Thanks. > Something like this: > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index ed1581b670d4..db5f72b94422 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -3029,21 +3029,9 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h, > { > gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE; > int nid = folio_nid(old_folio); > - struct folio *new_folio; > + struct folio *new_folio = NULL; > int ret = 0; > > - /* > - * Before dissolving the folio, we need to allocate a new one for the > - * pool to remain stable. Here, we allocate the folio and 'prep' it > - * by doing everything but actually updating counters and adding to > - * the pool. This simplifies and let us do most of the processing > - * under the lock. > - */ > - new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL); > - if (!new_folio) > - return -ENOMEM; > - __prep_new_hugetlb_folio(h, new_folio); > - > retry: > spin_lock_irq(&hugetlb_lock); > if (!folio_test_hugetlb(old_folio)) { > @@ -3073,6 +3061,15 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h, > cond_resched(); > goto retry; > } else { > + > + if (!new_folio) { > + spin_unlock_irq(&hugetlb_lock); > + new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL); > + if (!new_folio) > + return -ENOMEM; > + __prep_new_hugetlb_folio(h, new_folio); > + goto retry; > + } > /* > * Ok, old_folio is still a genuine free hugepage. Remove it from > * the freelist and decrease the counters. These will be > @@ -3100,9 +3097,11 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h, > > free_new: > spin_unlock_irq(&hugetlb_lock); > - /* Folio has a zero ref count, but needs a ref to be freed */ > - folio_ref_unfreeze(new_folio, 1); > - update_and_free_hugetlb_folio(h, new_folio, false); > + if (new_folio) { > + /* Folio has a zero ref count, but needs a ref to be freed */ > + folio_ref_unfreeze(new_folio, 1); > + update_and_free_hugetlb_folio(h, new_folio, false); > + } > > return ret; > }