https://bugzilla.kernel.org/show_bug.cgi?id=219166 Bug ID: 219166 Summary: ext4 hang when setting echo noop > /sys/block/sda/queue/scheduler Product: File System Version: 2.5 Hardware: All OS: Linux Status: NEW Severity: normal Priority: P3 Component: ext4 Assignee: fs_ext4@xxxxxxxxxxxxxxxxxxxx Reporter: rjones@xxxxxxxxxx Regression: No kernel-6.11.0-0.rc3.30.fc41.x86_64 This hang seems new in 6.11.0. Downstream bug: https://bugzilla.redhat.com/show_bug.cgi?id=2303267 Trying to change the queue/scheduler for a device containing an ext4 filesystem very rarely causes other processes which are using the filesystem to hang. This is running inside qemu. Using 'crash' I was able to get a stack trace from a couple of hanging processes (from different VM instances): crash> set 230 PID: 230 COMMAND: "modprobe" TASK: ffff98ce03ca3040 [THREAD_INFO: ffff98ce03ca3040] CPU: 0 STATE: TASK_UNINTERRUPTIBLE crash> bt PID: 230 TASK: ffff98ce03ca3040 CPU: 0 COMMAND: "modprobe" #0 [ffffaf9940307840] __schedule at ffffffff9618f6d0 #1 [ffffaf99403078f8] schedule at ffffffff96190a27 #2 [ffffaf9940307908] __bio_queue_enter at ffffffff957e121c #3 [ffffaf9940307968] blk_mq_submit_bio at ffffffff957f358c #4 [ffffaf99403079f0] __submit_bio at ffffffff957e1e3c #5 [ffffaf9940307a58] submit_bio_noacct_nocheck at ffffffff957e2326 #6 [ffffaf9940307ac0] ext4_mpage_readpages at ffffffff955ceafc #7 [ffffaf9940307be0] read_pages at ffffffff95381d1a #8 [ffffaf9940307c40] page_cache_ra_unbounded at ffffffff95381ff5 #9 [ffffaf9940307ca8] filemap_fault at ffffffff953761b5 #10 [ffffaf9940307d48] __do_fault at ffffffff953d1895 #11 [ffffaf9940307d70] do_fault at ffffffff953d2425 #12 [ffffaf9940307da0] __handle_mm_fault at ffffffff953d8c6b #13 [ffffaf9940307e88] handle_mm_fault at ffffffff953d95c2 #14 [ffffaf9940307ec8] do_user_addr_fault at ffffffff950b34ea #15 [ffffaf9940307f28] exc_page_fault at ffffffff96186e4e #16 [ffffaf9940307f50] asm_exc_page_fault at ffffffff962012a6 RIP: 0000556b7a7468d8 RSP: 00007ffde2ffb560 RFLAGS: 00000206 RAX: 00000000000bec82 RBX: 00007f5331a0dc82 RCX: 0000556b7a75b92a RDX: 00007ffde2ffd8d0 RSI: 00000000200bec82 RDI: 0000556ba8edf960 RBP: 00007ffde2ffb7c0 R8: 0000000000000000 R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00000000200bec82 R13: 0000556ba8edf960 R14: 00007ffde2ffd8d0 R15: 0000556b7a760708 ORIG_RAX: ffffffffffffffff CS: 0033 SS: 002b crash> set 234 PID: 234 COMMAND: "modprobe" TASK: ffff9f5ec3a22f40 [THREAD_INFO: ffff9f5ec3a22f40] CPU: 0 STATE: TASK_UNINTERRUPTIBLE crash> bt PID: 234 TASK: ffff9f5ec3a22f40 CPU: 0 COMMAND: "modprobe" #0 [ffffb21e002e7840] __schedule at ffffffffa718f6d0 #1 [ffffb21e002e78f8] schedule at ffffffffa7190a27 #2 [ffffb21e002e7908] __bio_queue_enter at ffffffffa67e121c #3 [ffffb21e002e7968] blk_mq_submit_bio at ffffffffa67f358c #4 [ffffb21e002e79f0] __submit_bio at ffffffffa67e1e3c #5 [ffffb21e002e7a58] submit_bio_noacct_nocheck at ffffffffa67e2326 #6 [ffffb21e002e7ac0] ext4_mpage_readpages at ffffffffa65ceafc #7 [ffffb21e002e7be0] read_pages at ffffffffa6381d17 #8 [ffffb21e002e7c40] page_cache_ra_unbounded at ffffffffa6381ff5 #9 [ffffb21e002e7ca8] filemap_fault at ffffffffa63761b5 #10 [ffffb21e002e7d48] __do_fault at ffffffffa63d1892 #11 [ffffb21e002e7d70] do_fault at ffffffffa63d2425 #12 [ffffb21e002e7da0] __handle_mm_fault at ffffffffa63d8c6b #13 [ffffb21e002e7e88] handle_mm_fault at ffffffffa63d95c2 #14 [ffffb21e002e7ec8] do_user_addr_fault at ffffffffa60b34ea #15 [ffffb21e002e7f28] exc_page_fault at ffffffffa7186e4e #16 [ffffb21e002e7f50] asm_exc_page_fault at ffffffffa72012a6 RIP: 000055d16159f8d8 RSP: 00007ffdd4c1f340 RFLAGS: 00010206 RAX: 00000000000bec82 RBX: 00007ff2fd00dc82 RCX: 000055d1615b492a RDX: 00007ffdd4c216b0 RSI: 00000000200bec82 RDI: 000055d185725960 RBP: 00007ffdd4c1f5a0 R8: 0000000000000000 R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00000000200bec82 R13: 000055d185725960 R14: 00007ffdd4c216b0 R15: 000055d1615b9708 ORIG_RAX: ffffffffffffffff CS: 0033 SS: 002b The hanging process was modprobe both times. I don't know if that is significant. Note that "noop" is not actually a valid scheduler (for about 10 years)! We still observe this hang even when setting it to this impossible value. # echo noop > /sys/block/sda/queue/scheduler /init: line 108: echo: write error: Invalid argument -- You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.
