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Wong" , Theodore Ts'o , Alexander Viro , Miklos Szeredi , Andrew Morton , Chaitanya Kulkarni CC: , , , , LKML , John Hubbard Subject: [RFC PATCH 6/7] fuse: convert direct IO paths to use FOLL_PIN Date: Fri, 25 Feb 2022 00:50:24 -0800 Message-ID: <20220225085025.3052894-7-jhubbard@nvidia.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220225085025.3052894-1-jhubbard@nvidia.com> References: <20220225085025.3052894-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: e14dc0c9-f000-4920-5c71-08d9f83be98e X-MS-TrafficTypeDiagnostic: CH0PR12MB5074:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:12.22.5.235;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230001)(4636009)(40470700004)(46966006)(36840700001)(70206006)(2906002)(40460700003)(86362001)(82310400004)(70586007)(426003)(7416002)(8936002)(107886003)(6666004)(186003)(2616005)(1076003)(26005)(83380400001)(508600001)(336012)(54906003)(966005)(921005)(356005)(316002)(6636002)(81166007)(110136005)(36860700001)(47076005)(8676002)(36756003)(4326008)(5660300002)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Feb 2022 08:50:45.3097 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e14dc0c9-f000-4920-5c71-08d9f83be98e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.235];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT007.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH0PR12MB5074 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Convert the fuse filesystem to support the new iov_iter_get_pages() behavior. That routine now invokes pin_user_pages_fast(), which means that such pages must be released via unpin_user_page(), rather than via put_page(). This commit also removes any possibility of kernel pages being handled, in the fuse_get_user_pages() call. Although this may seem like a steep price to pay, Christoph Hellwig actually recommended it a few years ago for nearly the same situation [1]. [1] https://lore.kernel.org/kvm/20190724061750.GA19397@infradead.org/ Signed-off-by: John Hubbard --- fs/fuse/dev.c | 5 ++++- fs/fuse/file.c | 23 ++++++++--------------- 2 files changed, 12 insertions(+), 16 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index e1b4a846c90d..a93037c96b89 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -675,7 +675,10 @@ static void fuse_copy_finish(struct fuse_copy_state *cs) flush_dcache_page(cs->pg); set_page_dirty_lock(cs->pg); } - put_page(cs->pg); + if (cs->pipebufs) + put_page(cs->pg); + else + unpin_user_page(cs->pg); } cs->pg = NULL; } diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 94747bac3489..395c2fb613fb 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -619,7 +619,7 @@ static void fuse_release_user_pages(struct fuse_args_pages *ap, for (i = 0; i < ap->num_pages; i++) { if (should_dirty) set_page_dirty_lock(ap->pages[i]); - put_page(ap->pages[i]); + unpin_user_page(ap->pages[i]); } } @@ -1382,20 +1382,13 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii, size_t nbytes = 0; /* # bytes already packed in req */ ssize_t ret = 0; - /* Special case for kernel I/O: can copy directly into the buffer */ - if (iov_iter_is_kvec(ii)) { - unsigned long user_addr = fuse_get_user_addr(ii); - size_t frag_size = fuse_get_frag_size(ii, *nbytesp); - - if (write) - ap->args.in_args[1].value = (void *) user_addr; - else - ap->args.out_args[0].value = (void *) user_addr; - - iov_iter_advance(ii, frag_size); - *nbytesp = frag_size; - return 0; - } + /* + * TODO: this warning can eventually be removed. It is just to help + * developers, during a transitional period, while direct IO code is + * moving over to FOLL_PIN pages. + */ + if (WARN_ON_ONCE(!iter_is_iovec(ii))) + return -EOPNOTSUPP; while (nbytes < *nbytesp && ap->num_pages < max_pages) { unsigned npages;