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Wed, 26 Aug 2026 13:57:24 +0000 (GMT) Received: from p-imbrenda (unknown [9.224.75.30]) by smtpav03.fra02v.mail.ibm.com (Postfix) with SMTP; Wed, 26 Aug 2026 13:57:24 +0000 (GMT) Date: Wed, 26 Aug 2026 15:57:22 +0200 From: Claudio Imbrenda To: Hugh Dickins Cc: Andrew Morton , Ackerley Tng , Alexander Viro , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , David Hildenbrand , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Kiryl Shutsemau , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yu Zhao , "Zach O'Keefe" , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 20/25] s390/fbatch: no lru_add_drain_all() in s390_wiggle_split_folio() Message-ID: <20260826155722.0198d3ce@p-imbrenda> In-Reply-To: <7bf68e7b-f88c-6ca9-39ab-e9fedab0c8be@google.com> References: <14a16945-529b-8bc0-ab38-3ea97e54e223@google.com> <7bf68e7b-f88c-6ca9-39ab-e9fedab0c8be@google.com> Organization: IBM X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwODI2MDExMiBTYWx0ZWRfX6oBMoAXUz9b+ R2tF2RTZdZcuqOBhxLba2axaGWhWg2Kl07rlyQKuFHwjSqkOxhSrWknwqzByANHgzXMIgsDlaEU Idl+30dokbx5c7aGM1azQMrbbL2NzlU= X-Proofpoint-GUID: ic4DR_A9PttbjD9aBnZ6wMO72ql0cvfP X-Proofpoint-ORIG-GUID: CtVKpmKXa-6fjrMbMK0sces9C8ZO455o X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI2MDExMiBTYWx0ZWRfX7/j9vZ3raXyB Me/IVg+MC4rfQk452IoupMj8YDfCrRb2aDsOD5v2ra95DbPAkxcv7e6jEP0qwG0PZO4yv1Dhl8A MDor97CDbv2jWwZubFtFo71f50APNaOXyPErDM8wuF9ANlsKg4R8mN1ETfKeEs7LY/eu1rcSswR ujmCkelqB5shvDHGHK7KQOqUTjGxr+/PE2dnk7Tzh0Q9LtWA/LNTZI2nOT5w+ACGn+182t/6tXK bPa8WHzBebLfwFyGylResRBGUAtgIcfqoeAZhfcwRefUAXVTJ8Ojiq7mZr55C0JybbHa7HV8jvi 8uJw1ELRQYwi4ziuvlfXVFScGfFjx3IZg7prbBCfBy1ZK0LLB7Ui/X3wJ8bY09SA4c4pI3mYqwv qNrzli/jLZlc8rSiWLGU7lnDa8/sZ5pE5EOrVG5HVnBjdZ3HWdNB9DZb6M4ma79dfwpc/F0B57l J4jca6EyH0POQCLZBWQ== X-Authority-Analysis: v=2.4 cv=H7brBeYi c=1 sm=1 tr=0 ts=6a8ef0c9 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=1XWaLZrsAAAA:8 a=67rAruxoP-Qw-q3ESxAA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-26_03,2026-08-26_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 spamscore=0 bulkscore=0 adultscore=0 priorityscore=1501 clxscore=1011 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608260112 On Mon, 24 Aug 2026 07:39:12 -0700 (PDT) Hugh Dickins wrote: > s390_wiggle_split_folio() has no good reason to lru_add_drain_all(), > now that the per-cpu fbatch references are gone. > > Signed-off-by: Hugh Dickins > --- > arch/s390/kernel/uv.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index dc14ebc0105b..120a467026a5 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -364,7 +364,6 @@ int s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio) > > lockdep_assert_not_held(&mm->mmap_lock); > folio_wait_writeback(folio); > - lru_add_drain_all(); > > if (!folio_test_large(folio)) > return 0; This is black magic for me, I am not sure I fully understand all the details, but what's the new purpose of lru_add_drain_all() ? will we have a guarantee that no stray references to mapped folios will ever remain? Any unexpected reference (i.e. not due to mappings, see expected_folio_refs()) will cause a protected guest to hang.