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Wed, 13 Dec 2023 13:57:34 GMT Received: from [10.216.55.196] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Wed, 13 Dec 2023 05:57:31 -0800 Message-ID: <05b4b5ab-a075-e693-7182-2477b40745dd@quicinc.com> Date: Wed, 13 Dec 2023 19:27:28 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH] [RFC] mm: migrate: rcu stalls because of invalid swap cache entries Content-Language: en-US From: Charan Teja Kalla To: Matthew Wilcox CC: , , , , , , , References: <1700569840-17327-1-git-send-email-quic_charante@quicinc.com> <51f727a2-75e9-d42f-bae6-d3e4c3328af1@quicinc.com> In-Reply-To: <51f727a2-75e9-d42f-bae6-d3e4c3328af1@quicinc.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: 6epGjchljk1wYzS80vb1f4JE1uhRYoii X-Proofpoint-GUID: 6epGjchljk1wYzS80vb1f4JE1uhRYoii X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-09_01,2023-12-07_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 priorityscore=1501 impostorscore=0 mlxscore=0 clxscore=1011 mlxlogscore=635 bulkscore=0 spamscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2311290000 definitions=main-2312130101 X-Rspamd-Queue-Id: CA7E840014 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 1dumge69s9k41sguxp6jwnm6hjiq7p3m X-HE-Tag: 1702475870-736227 X-HE-Meta: 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 LxXGrBS5 pAORVRzHoS5xnjg0WkcjchP7dFC8k8gLG5mFkABKzJ3gppnRokkQJy1dgMJ5OJzN/VAp8bKn6bQMkOUDFcXDvfKtLxZdKPsgqxkDgxlDxU84/LrJtTwoLFX38utsmxaLIHpx2kgxRoAEpLFIYz8MwPj+s0z/a8v33vEGpxe+jLxdzbgjqjNK24fB8Cpzim5gYtSsYpH+mjRCPN4bklaw7hmPfQQrQaMUSqVJ7nuMqfeIJHHM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: HI Matthew, Just a ping to have your valuable opinion here. Thanks, Charan On 11/23/2023 7:55 PM, Charan Teja Kalla wrote: >> What would you think to this? I think a better fix would be to >> fix the swap cache to user multi-order entries, but I would like to >> see this backportable! >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index d9d2b9432e81..2d67ca47d2e2 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -405,6 +405,7 @@ int folio_migrate_mapping(struct address_space *mapping, >> int dirty; >> int expected_count = folio_expected_refs(mapping, folio) + extra_count; >> long nr = folio_nr_pages(folio); >> + long entries, i; >> >> if (!mapping) { >> /* Anonymous page without mapping */ >> @@ -442,8 +443,10 @@ int folio_migrate_mapping(struct address_space *mapping, >> folio_set_swapcache(newfolio); >> newfolio->private = folio_get_private(folio); >> } >> + entries = nr; >> } else { >> VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); >> + entries = 1; >> } >> >> /* Move dirty while page refs frozen and newpage not yet exposed */ >> @@ -453,7 +456,11 @@ int folio_migrate_mapping(struct address_space *mapping, >> folio_set_dirty(newfolio); >> } >> >> - xas_store(&xas, newfolio); >> + /* Swap cache still stores N entries instead of a high-order entry */ >> + for (i = 0; i < entries; i++) { >> + xas_store(&xas, newfolio); >> + xas_next(&xas); >> + } >> >> /* >> * Drop cache reference from old page by unfreezing > Seems a cleaner one to store N entries. Supporting swap cache for multi > order entries might be time consuming. Till then, can we use this patch > as the solution, with the proper commit log conveying revert of this > patch when swap cache supported with Multi-order indices? > > Please Lmk, If I can raise this patch with suggested-by:you