A write that fails with ENOSPC on the image is held and retried by enospc_timer, so that I/O resumes once space is freed. The timer only sets a flag that the dispatcher consumes, and nothing wakes the dispatcher, so the held writes are retried only when other I/O reaches the device. On a device whose only I/O is the held writes, the writers stay in D state for good after the space is freed (patch 2, VSTOR-154182).
Patch 1 makes the destructor shut the timer down first. Nothing stops it there today, and with patch 2 the callback dereferences the dispatcher thread as well as struct ploop. Found in a vmcore: 16 writers in D state, submit_enospc set, all 16 pios on enospc_pios, the timer expired 12 s before the crash. Tested on 6.12.0-211.52.1.22.19.vz10, dm-ploop built out of tree: - 16 O_DIRECT writers held on a full host ext4, then the space freed with no other I/O on the device. Stock: still stuck after 60 s, one unrelated read releases them. With the series: done 8 s after the space is freed, on the next timer tick; - ploop test suite, make -j48 test on dev-cl04, green for ploop and qcow2 with this series together with the VSTOR-154096 one. Denis V. Lunev (2): dm-ploop: stop enospc_timer in ploop_destroy() dm-ploop: fix the ENOSPC retry timer not waking the dispatcher drivers/md/dm-ploop-map.c | 9 +++++---- drivers/md/dm-ploop-target.c | 1 + 2 files changed, 6 insertions(+), 4 deletions(-) -- 2.53.0 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
