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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oneplus.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7c65014b-7e56-439f-13e6-08d6901ff8ea X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Feb 2019 12:53:50.0069 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-id: 0423909d-296c-463e-ab5c-e5853a518df8 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SL2PR04MB3081 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In 4.14 kernel, observed following 2 BUG_ON(!PageLocked(page)) scenarios. Both looks to be having similar cause. Case: 1 [127823.176076] try_to_free_buffers+0xfc/0x108 (BUG_ON(), page lock was fre= ed somehow) [127823.176079] jbd2_journal_try_to_free_buffers+0x15c/0x194 (page lock was available till this function) [127823.176083] ext4_releasepage+0xe0/0x110=20 [127823.176087] try_to_release_page+0x68/0x90 (page lock was available till this function) [127823.176090] invalidate_inode_page+0x94/0xa8 [127823.176093] invalidate_mapping_pages_without_uidlru+0xec/0x1a4 (page lo= ck taken here) ... ... Case: 2 [] el1_dbg+0x18 [] __remove_mapping+0x160 (BUG_ON(), page lock is not available. Some one might have free'd that.) [] remove_mapping+0x28 [] invalidate_inode_page+0xa4 [] invalidate_mapping_pages+0xd4 (acquired the page lock= ) [] inode_lru_isolate+0x128 [] __list_lru_walk_one+0x10c [] list_lru_walk_one+0x58 [] prune_icache_sb+0x50 [] super_cache_scan+0xfc [] shrink_slab+0x304 [] shrink_node+0x254 [] do_try_to_free_pages+0x144 [] try_to_free_pages+0x390 [] __alloc_pages_nodemask+0x940 [] __get_free_pages+0x28 [] proc_pid_readlink+0x6c [] vfs_readlink+0x124 [] SyS_readlinkat+0xc8 [] __sys_trace_return+0x0 Both the scenarios say that current stack tried taking page lock but got released in meantime by someone else. There could be 2 possiblities here. 1) Someone trying to update page flags and due to race condition, PG_locked bit got cleared, unwantedly. 2) Someone else took the lock without checking if it is really locked or no= t as there are explicit APIs to set PG_locked. I didn't get traces of history for having PG_locked being set non-atomicall= y. I believe it could be because of performance reasons. Not sure though. Chintan Pandya (2): page-flags: Make page lock operation atomic page-flags: Catch the double setter of page flags fs/cifs/file.c | 8 ++++---- fs/pipe.c | 2 +- include/linux/page-flags.h | 4 ++-- include/linux/pagemap.h | 6 +++--- mm/filemap.c | 4 ++-- mm/khugepaged.c | 2 +- mm/ksm.c | 2 +- mm/memory-failure.c | 2 +- mm/memory.c | 2 +- mm/migrate.c | 2 +- mm/shmem.c | 6 +++--- mm/swap_state.c | 4 ++-- mm/vmscan.c | 2 +- 13 files changed, 23 insertions(+), 23 deletions(-) --=20 2.17.1