From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout12.his.huawei.com (canpmsgout12.his.huawei.com [113.46.200.227]) (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 B0017285058 for ; Wed, 26 Aug 2026 01:46:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.227 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787708777; cv=none; b=TPTkgF7RYBBcwvPvkrv9a3zCasKuPNXAEJkLI5oCKoFb0lOfKZm4FeJ+QQeAuFL6pCyVJaQ2K7tm4aFpjc7Dijyah30Zm2JVWm+WU1qFA6AxcnHlBuv7cPiPx1r/gKj/IDi3AKRaGyBEHOBCXTipcvcscVjpOSRPvI7/i+NN0OY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787708777; c=relaxed/simple; bh=pNLy1xt8ltkuAvGKcOPrV/veieNd3MG2JijHcWPQBq4=; h=Message-ID:Date:MIME-Version:From:Subject:To:CC:References: In-Reply-To:Content-Type; b=L89MBnRp64qdEoZ5Ao4W01WvL0Fi/625qzBPldczezou8AtROIbkhTY3tSQkFdReZtwXYuUkb43HPX2JFcUsi013axoEgXCv7J3lB4unHLYfZIO7O49ZPwrqPJQMCP4x89qAu0jP48p2ii0ZDU4p25QfdINP5G1zkjMlRncDmwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=2kDdgKCD; arc=none smtp.client-ip=113.46.200.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="2kDdgKCD" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=TFA8gg4dXqO5eQ3Z8uhoSt39gt9y9DRKmtEs9LVCGbE=; b=2kDdgKCDMdGoIbhTaF3zE1+No3dQ1vaJ/+5famVqMY51YU9VWaYD/+nBgazTKGSTDsT+980PG eTlc5iw7TG79G7i4+olp6ThK21Husf+OfbBlXMHCo0HT/O5HUG1B7CHqv5COzxDFQJ4vRHXvgWJ /PZqVYjNGG3lBxpHPtpYFeA= Received: from mail.maildlp.com (unknown [172.19.163.15]) by canpmsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4hV6fy5P50znTtT; Wed, 26 Aug 2026 09:35:54 +0800 (CST) Received: from whupemk200018.china.huawei.com (unknown [7.152.184.119]) by mail.maildlp.com (Postfix) with ESMTPS id 5FFFB40578; Wed, 26 Aug 2026 09:46:09 +0800 (CST) Received: from [10.174.177.15] (10.174.177.15) by whupemk200018.china.huawei.com (7.152.184.119) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Wed, 26 Aug 2026 09:46:08 +0800 Message-ID: Date: Wed, 26 Aug 2026 09:46:07 +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 From: mawupeng Subject: Re: [PATCH] mm/hugetlb: fix missing migratable flag on same-node hugetlb migration To: , , , , CC: , , References: <20260707110254.3147686-1-mawupeng1@huawei.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To whupemk200018.china.huawei.com (7.152.184.119) On 周二 2026-8-25 18:27, David Hildenbrand (Arm) wrote: > On 7/7/26 13:02, Wupeng Ma wrote: >> Commit ba23f58de896 ("mm/migrate: don't call >> folio_putback_active_hugetlb() on dst hugetlb folio") moved setting of >> the migratable flag and active-list placement from >> folio_putback_active_hugetlb(dst) into move_hugetlb_state(), so that >> the freshly allocated destination folio is handled where allocation is >> known to have succeeded. >> >> Unfortunately, the new code was appended after the existing >> temporary-folio block in move_hugetlb_state(), which contains an early >> return added earlier by commit 5af1ab1d24e08 ("mm/hugetlb: optimize >> the surplus state transfer code in move_hugetlb_state()"): >> >> if (folio_test_hugetlb_temporary(new_folio)) { >> ... >> if (new_nid == old_nid) >> return; <-- skips the new code >> ... >> } >> >> /* added by ba23f58 */ >> folio_set_hugetlb_migratable(new_folio); >> list_move_tail(&new_folio->lru, ...&h->hugepage_activelist); >> >> When the destination folio is temporary (i.e. the hugetlb pool was >> exhausted and the migration callback fell back to >> alloc_migrate_hugetlb_folio()) and the migration does not cross a >> node -- the common case, and always true on a single-NUMA system -- >> move_hugetlb_state() returns before setting the migratable flag or >> adding the new folio to the active list. The destination folio is >> then installed in the page table but cannot be isolated afterwards, >> since folio_isolate_hugetlb() rejects folios without the migratable >> flag; a subsequent soft-offline, hard-offline or memory-hotplug >> offline of that folio fails with -EBUSY. >> >> This was reproduced on a single-NUMA arm64 VM: a second >> MADV_SOFT_OFFLINE on an already-migrated hugetlb page returned EBUSY >> and logged "hugepage isolation failed". >> >> Keep the surplus adjustment, which is the only part that depends on >> the node crossing, guarded by `if (new_nid != old_nid)', while making >> the migratable flag and active-list placement unconditional. This >> preserves the cleanup intent of ba23f58 and closes the early-return >> hole. >> >> Fixes: ba23f58de896 ("mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio") > > Agreed, let's CC stable. Thanks. > >> Signed-off-by: Wupeng Ma >> --- >> mm/hugetlb.c | 14 +++++++------- >> 1 file changed, 7 insertions(+), 7 deletions(-) >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 571212b80835..cafadfdb63c0 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -7211,14 +7211,14 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int re >> * There is no need to transfer the per-node surplus state >> * when we do not cross the node. >> */ >> - if (new_nid == old_nid) >> - return; >> - spin_lock_irq(&hugetlb_lock); >> - if (h->surplus_huge_pages_node[old_nid]) { >> - h->surplus_huge_pages_node[old_nid]--; >> - h->surplus_huge_pages_node[new_nid]++; >> + if (new_nid != old_nid) { >> + spin_lock_irq(&hugetlb_lock); >> + if (h->surplus_huge_pages_node[old_nid]) { >> + h->surplus_huge_pages_node[old_nid]--; >> + h->surplus_huge_pages_node[new_nid]++; >> + } >> + spin_unlock_irq(&hugetlb_lock); >> } > > The return was really rather hidden, thanks! > > Can't we instead just turn the "return;" into a "continue;" ? There’s no loop in move_hugetlb_state(), so continue won’t work there. But I understand your intention. To be honest, I’m not fully satisfied with the nested if either, but I haven’t found a cleaner way. goto, or extracting the surplus move into a helper, feels like over-engineering. >