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Tue, 2 Feb 2021 04:11:35 +0000 Subject: Re: [PATCH] fuse: avoid deadlock when write fuse inode To: fuse-devel@lists.sourceforge.net Cc: guoweichao@oppo.com, zhangshiming@oppo.com, linux-kernel@vger.kernel.org References: <20210202040830.26043-1-huangjianan@oppo.com> From: Huang Jianan Message-ID: Date: Tue, 2 Feb 2021 12:11:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 In-Reply-To: <20210202040830.26043-1-huangjianan@oppo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [58.252.5.72] X-ClientProxiedBy: HK0PR03CA0109.apcprd03.prod.outlook.com (2603:1096:203:b0::25) To SG2PR02MB4108.apcprd02.prod.outlook.com (2603:1096:4:96::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.118.0.32] (58.252.5.72) by HK0PR03CA0109.apcprd03.prod.outlook.com (2603:1096:203:b0::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?eFYvYnl1MWJyNHRoLytkeE16bXNjZ1ZNcVBnSjRTNHZWV0ZtQ0Y0dmpzQ0dp?= =?utf-8?B?OFZ3TkRpMVhIL0p1QjJDeUVONG5TVWtpZndoZ1RZa0JaNERNYXNxdWFNcXFV?= =?utf-8?B?R09wK0xIRC80b2JaUy80TFA2Mm9Wd2dLeWhYWE1iUUdXaEdtWjFXZUY4bW9a?= =?utf-8?B?T0Rwc2QxRVhJSURiU1VJU1dlQ0txWkpLUVJjelprdnhzQlpza2tKb1l4Q2N0?= =?utf-8?B?aHo4M2cwTUExMnFyTWhOdkVQVElhSVQ5WHBsTXlSSzNQR3JVUW5IZmxuczQx?= =?utf-8?B?cHhaS2FIWTRVRGs4bGZMelJuN2t6VWVBTUtuN2krRysyc0dmWThrenhhdTBy?= =?utf-8?B?cjY1dGtHSUlsV3luRWttQWF6cjAzR0dEZTdIdkNHMkgva3c2aHRmYzluaS9O?= =?utf-8?B?NXY2NHZVdmpzeE81bjdZTUVsTll3SFZWRTRSSG5taXl1ZWg0OHlyNkZyQjJo?= =?utf-8?B?QTE4Y1N5VGZCeHBqV2tiTTA5eTRTbit6SnFUUnpZVERhZGF3NzNndUY3cVVW?= =?utf-8?B?aGZ4NjU3djBEQ21PTDRucldMdzBmWVBiUm5yKzBXNzBQM3NaTFhPY0dCc1VR?= =?utf-8?B?MjZCMnUrTmh2MS9YanMyZlQrZ09rREI2V3p5aDFYRVlMQnBlQnBubEVjdW8y?= =?utf-8?B?SEdzMkMyMGdzcWpYTGd4ZmVYTUt4K1NOemRTQnFLejZ5OXJ4TS9GN2htN29a?= =?utf-8?B?YkEvMElxcmRKYzZhdzBYbHI4cUJVRnA3UDB3SndHbFdZWTZpNEo3NVFxUVdP?= =?utf-8?B?Wm5SSjV5L2d6RGk4bU1adjBmSDUxUGFHUlo5bU9LY0RiM1ZvbUVWK3ZOSFNT?= =?utf-8?B?cEt2Wnd1WDdXSHRBM1VRWlJOMFo3VnFYQWNoN1R3SkdOSkJlQTlyelZaR3hW?= =?utf-8?B?cnBSWG5zclBSUlNDZnJOZ2FnUUU3NGY1b1hxZDNSU2ZBaWMrV0RkVEFGQU1C?= =?utf-8?B?ZDBpQXZrUGlVU2k2aFU1QUFDekJBeVlCS2Q4azlxNHJxWERzbjUvVDdzTnNT?= =?utf-8?B?ay9ybHhObmxaMDVPTXVsaXZ4NjFPcXRyN3RzRkhZSDNkc0JHMXhIdEF6V3I3?= =?utf-8?B?VVR4MUZlUE1SZEZUdzQ1ZWdQS01EUEE2MHNkTkZXRkxRaFNhTi9iMjFPR3BY?= =?utf-8?B?YzVMVi9seTlqVWRUeEZteXlsQ0cvbjBZZHhEcklyamFCTnEyWjhWQTdYWmZr?= =?utf-8?B?T3dVVE9uTWhzcU1QbjM0UTVNUWJEME5xRkl5elkwWHNBNmVMa0RaS0N3TjZX?= =?utf-8?B?UURsL3IvcFdBL1ZBajRPaWEwbzBPTThJd0dOZHlFRU4zemdHRzZXYnhYbFZO?= =?utf-8?B?d2VhSnl1K0hPNitPTGVHY09WTDd6anF4UnlWViszZ2hiZlNmbWhZVnJsbkJo?= =?utf-8?B?eXRHSWM0RjF2czBtUlZwaUpYUGxHWlNDcjBodlBtcE5ldzFDaURKVERHUXkv?= =?utf-8?Q?bU3SzrO0?= X-OriginatorOrg: oppo.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6fe0f236-95f2-4d00-ee0b-08d8c730a14a X-MS-Exchange-CrossTenant-AuthSource: SG2PR02MB4108.apcprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Feb 2021 04:11:35.2474 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f1905eb1-c353-41c5-9516-62b4a54b5ee6 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: TRvzQA2dv2CFvW2eazTGp5J5UcHjUXL4JG17d4dzlx9/byj5Oy27lk3SI2mlxxMzNPjbhm2pSC7bPtLpAqqw9A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2PR02MB2699 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, This patch works well in our product, but I am not sure this is the correct way to solve this problem. I think that the inode->i_count shouldn't be zero after iput is executed in dentry_unlink_inode, then the inode won't be writeback. But i haven't found where iget is missing. Thanks, Jianan On 2021/2/2 12:08, Huang Jianan wrote: > We found the following deadlock situations in low memory scenarios: > Thread A Thread B > - __writeback_single_inode > - fuse_write_inode > - fuse_simple_request > - __fuse_request_send > - request_wait_answer > - fuse_dev_splice_read > - fuse_copy_fill > - __alloc_pages_direct_reclaim > - do_shrink_slab > - super_cache_scan > - shrink_dentry_list > - dentry_unlink_inode > - iput_final > - inode_wait_for_writeback > > The request and inode processed by Thread A and B are the same, which > causes a deadlock. To avoid this, we remove the __GFP_FS flag when > allocating memory in fuse_copy_fill, so there will be no memory > reclaimation in super_cache_scan. > > Signed-off-by: Huang Jianan > Signed-off-by: Guo Weichao > --- > fs/fuse/dev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c > index 588f8d1240aa..e580b9d04c25 100644 > --- a/fs/fuse/dev.c > +++ b/fs/fuse/dev.c > @@ -721,7 +721,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs) > if (cs->nr_segs >= cs->pipe->max_usage) > return -EIO; > > - page = alloc_page(GFP_HIGHUSER); > + page = alloc_page(GFP_HIGHUSER & ~__GFP_FS); > if (!page) > return -ENOMEM; >