On 2018/05/14 23:36, syzbot wrote: > Call Trace: > context_switch kernel/sched/core.c:2859 [inline] > __schedule+0x801/0x1e30 kernel/sched/core.c:3501 > schedule+0xef/0x430 kernel/sched/core.c:3545 > __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:269 [inline] > rwsem_down_read_failed+0x350/0x5e0 kernel/locking/rwsem-xadd.c:286 > call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94 > __down_read arch/x86/include/asm/rwsem.h:83 [inline] > down_read+0xbd/0x1b0 kernel/locking/rwsem.c:26 > inode_lock_shared include/linux/fs.h:723 [inline] > ext4_direct_IO_read fs/ext4/inode.c:3828 [inline] > ext4_direct_IO+0x653/0x2110 fs/ext4/inode.c:3865 > generic_file_read_iter+0x510/0x2f00 mm/filemap.c:2341 > ext4_file_read_iter+0x18b/0x3c0 fs/ext4/file.c:77 > call_read_iter include/linux/fs.h:1778 [inline] > generic_file_splice_read+0x552/0x910 fs/splice.c:307 > do_splice_to+0x12e/0x190 fs/splice.c:880 > splice_direct_to_actor+0x268/0x8d0 fs/splice.c:952 > do_splice_direct+0x2cc/0x400 fs/splice.c:1061 > do_sendfile+0x60f/0xe00 fs/read_write.c:1440 > __do_sys_sendfile64 fs/read_write.c:1495 [inline] > __se_sys_sendfile64 fs/read_write.c:1487 [inline] > __x64_sys_sendfile64+0x155/0x240 fs/read_write.c:1487 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe This resembles Call Trace: context_switch kernel/sched/core.c:2848 [inline] __schedule+0x801/0x1e30 kernel/sched/core.c:3490 schedule+0xef/0x430 kernel/sched/core.c:3549 __rwsem_down_write_failed_common+0x919/0x15d0 kernel/locking/rwsem-xadd.c:566 rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0xa2/0x120 kernel/locking/rwsem.c:72 inode_lock include/linux/fs.h:713 [inline] ext4_file_write_iter+0x303/0x1420 fs/ext4/file.c:235 call_write_iter include/linux/fs.h:1784 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x64d/0x960 fs/read_write.c:487 vfs_write+0x1f8/0x560 fs/read_write.c:549 ksys_pwrite64+0x174/0x1a0 fs/read_write.c:652 __do_sys_pwrite64 fs/read_write.c:662 [inline] __se_sys_pwrite64 fs/read_write.c:659 [inline] __x64_sys_pwrite64+0x97/0xf0 fs/read_write.c:659 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe in the report below. INFO: task hung in ext4_file_write_iter https://syzkaller.appspot.com/bug?id=c7370ffdecb4c7c7a24a50e17acaf102850d43ab But I have no idea why usual file write causes problems. Since there is LOOP_CHANGE_FD request in the console output, maybe it is better to try 170785a9cc72e8e1 ("loop: add recursion validation to LOOP_CHANGE_FD") now and see whether it helps?
