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Thu, 30 Jul 2020 19:16:21 +0000 Date: Thu, 30 Jul 2020 12:16:18 -0700 From: Roman Gushchin To: Mike Kravetz CC: , , Marek Szyprowski , Michal Nazarewicz , Kyungmin Park , Barry Song , Andrew Morton , Subject: Re: [PATCH] cma: don't quit at first error when activating reserved areas Message-ID: <20200730191618.GA703407@carbon.DHCP.thefacebook.com> References: <20200730163123.6451-1-mike.kravetz@oracle.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200730163123.6451-1-mike.kravetz@oracle.com> X-ClientProxiedBy: BYAPR21CA0009.namprd21.prod.outlook.com (2603:10b6:a03:114::19) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:931) by BYAPR21CA0009.namprd21.prod.outlook.com (2603:10b6:a03:114::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3261.0 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 342230e7-2a34-4f22-df1a-08d834bd0ad9 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jul 2020 19:16:21.1107 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: AXMlSIXuWQzVTNPxrPd8P04o98jVBSLVJwJRv9rot4Iz2FjvJEQJ0kDKt3CWrI5Z X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2600 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-30_14:2020-07-30,2020-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 malwarescore=0 adultscore=0 suspectscore=1 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 bulkscore=0 clxscore=1011 mlxscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007300133 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 30, 2020 at 09:31:23AM -0700, Mike Kravetz wrote: > The routine cma_init_reserved_areas is designed to activate all > reserved cma areas. It quits when it first encounters an error. > This can leave some areas in a state where they are reserved but > not activated. There is no feedback to code which performed the > reservation. Attempting to allocate memory from areas in such a > state will result in a BUG. > > Modify cma_init_reserved_areas to always attempt to activate all > areas. The called routine, cma_activate_area is responsible for > leaving the area in a valid state. No one is making active use > of returned error codes, so change the routine to void. > > How to reproduce: This example uses kernelcore, hugetlb and cma > as an easy way to reproduce. However, this is a more general cma > issue. > > Two node x86 VM 16GB total, 8GB per node > Kernel command line parameters, kernelcore=4G hugetlb_cma=8G > Related boot time messages, > hugetlb_cma: reserve 8192 MiB, up to 4096 MiB per node > cma: Reserved 4096 MiB at 0x0000000100000000 > hugetlb_cma: reserved 4096 MiB on node 0 > cma: Reserved 4096 MiB at 0x0000000300000000 > hugetlb_cma: reserved 4096 MiB on node 1 > cma: CMA area hugetlb could not be activated > > # echo 8 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] SMP PTI > ... > Call Trace: > bitmap_find_next_zero_area_off+0x51/0x90 > cma_alloc+0x1a5/0x310 > alloc_fresh_huge_page+0x78/0x1a0 > alloc_pool_huge_page+0x6f/0xf0 > set_max_huge_pages+0x10c/0x250 > nr_hugepages_store_common+0x92/0x120 > ? __kmalloc+0x171/0x270 > kernfs_fop_write+0xc1/0x1a0 > vfs_write+0xc7/0x1f0 > ksys_write+0x5f/0xe0 > do_syscall_64+0x4d/0x90 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator") > Signed-off-by: Mike Kravetz > Cc: Makes total sense to me! Reviewed-by: Roman Gushchin Thanks!