From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5F6B93A7D9E for ; Tue, 25 Aug 2026 10:27:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787653665; cv=none; b=FD9qT1oDCCsjyhwVlX8gcaz0jxVAYTMCj411K+EP8pEq1sNKYlsQM0aLdBXCDHaGi6Hmro13Ta2nuId7hyqf/i9UGgyMxn1GGaaR9TjHQoOB5SCRYLXQWQzRuR90ezpyy7WuT4nA3j+BCB+Yfzy60gqBxfKxT24B8vFOHIVdfTA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787653665; c=relaxed/simple; bh=49Lj1gSFrHZaF39cjpxmri4V/2k+VISJAoixTFJoXeo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BVsSiVcn9k2R153kLJgBeRNb9T+5LVAZL4JIPQgTCJz3pX/XY7cxnOdH87HdSa9OtQOI/GgrjCGICGmI9etY4e2/YLUHHGIVfs6wuRy6vZ3RS7o9HfdeoWvrylP91/RoQa6QjdUn4jvkB/ce1scqVUnImKuMSdO9avi1ODNQzMY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ShPy4092; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ShPy4092" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E12F71F000E9; Tue, 25 Aug 2026 10:27:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787653664; bh=AmTIRDghT5aZb5UGuzctLRIrFioVqTHUxr0Sp616qgk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ShPy40928OrdedT4DDHV3NrG1zdtp2MAf0KfSjOriqJwJmwdEeebXZhjY+cP2bG2P DX24DZ2urmbwyD7akQHe+1sPrqr6SvuMKK2AK4T+u3tuHhzhSUtFVd3SlyGLPHZP7o uzFwIK7JLx1I4W702S7bhpj+DSm5lZETQqTbTsWzYkubU9wFJ64sUIFk4STrffBu5A sZBmGRklT2j1Em37fLf7jYrNhqyPiELdLO5jBis/uvJwAi1P+U9XCiDsHvtYDqLpu4 9ddSlAgY0CDyl4OLm66DB5z76DhHubcqRw7NHxEWgHWXTb81quv2FoS+kO52uUzrx5 L9srPGLmeeWEQ== Message-ID: Date: Tue, 25 Aug 2026 12:27:39 +0200 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 missing migratable flag on same-node hugetlb migration To: Wupeng Ma , muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, baolin.wang@linux.alibaba.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260707110254.3147686-1-mawupeng1@huawei.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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. > 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;" ? -- Cheers, David