Commits on Oct 9, 2014

1. vdev_raidz_io_start: Ignore empty writes …

   The below excerpt of a backtrace is from a ztest failure when running
   ZoL's ztest.
   
   /openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
   /openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
   /openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
   /openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
   /openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
   /openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
   /openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
   /openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
   /openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
   /openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
   /openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
   /openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
   /openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
   /openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
   /openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
   /openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
   /openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
   /openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
   /openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
   /openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
   /openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
   /openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
   /openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
   /openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
   /openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
   /openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
   /openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
   /openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
   /openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
   /openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
   /openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
   /openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
   /openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
   /openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
   /openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
   /openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
   /openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
   /openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
   /openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
   /openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
   /openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
   /openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
   /openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
   /openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
   /openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
   /openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
   /openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
   /openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
   /openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
   /openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
   /openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
   /openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
   /openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
   /openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
   /openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
   /openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
   /openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
   /openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
   /openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
   /openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
   /openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
   /openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
   /openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
   /openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
   /openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
   /openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
   /openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
   /openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
   /openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
   
   The backtrace was an infinite loop of `vdev_queue_io_to_issue()` invoking
   `zio_execute()` until it overran the stack. vdev_queue_io_to_issue() will ony
   invoke `zio_execute()` on raidz vdevs when aggregation I/Os are generated to
   improve aggregation continuity. These I/Os do not trigger any writes. However,
   it appears that they can be generated in such a way that they recurse
   infinitely upon return to `vdev_queue_io_to_issue()`.
   
   Signed-off-by: Richard Yao <richard.yao@clusterhq.com>

   

   ryao committed Oct 9, 2014
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