linux/drivers/block
Jens Axboe de7b75d82f floppy: fix race condition in __floppy_read_block_0()
LKP recently reported a hang at bootup in the floppy code:

[  245.678853] INFO: task mount:580 blocked for more than 120 seconds.
[  245.679906]       Tainted: G                T 4.19.0-rc6-00172-ga9f38e1 #1
[  245.680959] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  245.682181] mount           D 6372   580      1 0x00000004
[  245.683023] Call Trace:
[  245.683425]  __schedule+0x2df/0x570
[  245.683975]  schedule+0x2d/0x80
[  245.684476]  schedule_timeout+0x19d/0x330
[  245.685090]  ? wait_for_common+0xa5/0x170
[  245.685735]  wait_for_common+0xac/0x170
[  245.686339]  ? do_sched_yield+0x90/0x90
[  245.686935]  wait_for_completion+0x12/0x20
[  245.687571]  __floppy_read_block_0+0xfb/0x150
[  245.688244]  ? floppy_resume+0x40/0x40
[  245.688844]  floppy_revalidate+0x20f/0x240
[  245.689486]  check_disk_change+0x43/0x60
[  245.690087]  floppy_open+0x1ea/0x360
[  245.690653]  __blkdev_get+0xb4/0x4d0
[  245.691212]  ? blkdev_get+0x1db/0x370
[  245.691777]  blkdev_get+0x1f3/0x370
[  245.692351]  ? path_put+0x15/0x20
[  245.692871]  ? lookup_bdev+0x4b/0x90
[  245.693539]  blkdev_get_by_path+0x3d/0x80
[  245.694165]  mount_bdev+0x2a/0x190
[  245.694695]  squashfs_mount+0x10/0x20
[  245.695271]  ? squashfs_alloc_inode+0x30/0x30
[  245.695960]  mount_fs+0xf/0x90
[  245.696451]  vfs_kern_mount+0x43/0x130
[  245.697036]  do_mount+0x187/0xc40
[  245.697563]  ? memdup_user+0x28/0x50
[  245.698124]  ksys_mount+0x60/0xc0
[  245.698639]  sys_mount+0x19/0x20
[  245.699167]  do_int80_syscall_32+0x61/0x130
[  245.699813]  entry_INT80_32+0xc7/0xc7

showing that we never complete that read request. The reason is that
the completion setup is racy - it initializes the completion event
AFTER submitting the IO, which means that the IO could complete
before/during the init. If it does, we are passing garbage to
complete() and we may sleep forever waiting for the event to
occur.

Fixes: 7b7b68bba5 ("floppy: bail out in open() if drive is not responding to block0 read")
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-10 08:16:12 -07:00
..
aoe aoe: convert aoeblk to blk-mq 2018-10-14 12:47:52 -06:00
drbd Merge branch 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-11-01 19:58:52 -07:00
mtip32xx mtip32xx: clean an indentation issue, remove extraneous tabs 2018-10-30 14:31:36 -06:00
paride paride: convert pf to blk-mq 2018-10-15 20:08:15 -06:00
rsxx pci-v4.20-changes 2018-10-25 06:50:48 -07:00
xen-blkback xen/blkback: remove unused pers_gnts_lock from struct xen_blkif_ring 2018-08-27 12:12:04 -04:00
zram drivers/block: remove redundant 'default n' from Kconfig-s 2018-10-10 14:11:08 -06:00
amiflop.c amiflop: convert to blk-mq 2018-10-16 09:49:52 -06:00
ataflop.c ataflop: convert to blk-mq 2018-10-16 09:50:09 -06:00
brd.c block: brd: associate with queue until adding disk 2018-11-01 19:59:51 -06:00
cryptoloop.c block: cryptoloop: Remove VLA usage of skcipher 2018-09-28 12:46:07 +08:00
floppy.c floppy: fix race condition in __floppy_read_block_0() 2018-11-10 08:16:12 -07:00
Kconfig drivers/block: Remove DAC960 driver 2018-10-17 09:42:30 -06:00
loop.c for-linus-20181102 2018-11-02 11:25:48 -07:00
loop.h loop: remember whether sysfs_create_group() was done 2018-05-07 15:26:36 -06:00
Makefile drivers/block: Remove DAC960 driver 2018-10-17 09:42:30 -06:00
nbd.c iov_iter: Separate type from direction and use accessor functions 2018-10-24 00:41:07 +01:00
null_blk_main.c block: Introduce blk_revalidate_disk_zones() 2018-10-25 11:17:40 -06:00
null_blk_zoned.c block: add a report_zones method 2018-10-25 11:17:40 -06:00
null_blk.h block: add a report_zones method 2018-10-25 11:17:40 -06:00
pktcdvd.c pktcdvd: fix fall-through annotation 2018-10-02 08:36:58 -06:00
ps3disk.c ps3disk: convert to blk-mq 2018-10-15 20:07:56 -06:00
ps3vram.c block: genhd: add 'groups' argument to device_add_disk 2018-09-28 08:30:28 -06:00
rbd_types.h rbd: RBD_V{1,2}_DATA_FORMAT macros 2017-02-20 12:16:15 +01:00
rbd.c libceph, rbd, ceph: move ceph_osdc_alloc_messages() calls 2018-10-22 10:28:22 +02:00
skd_main.c skd: fix unchecked return values 2018-10-25 11:17:39 -06:00
skd_s1120.h skd: Use __packed only when needed 2017-08-18 08:45:29 -06:00
sunvdc.c for-4.20/block-20181021 2018-10-22 17:46:08 +01:00
swim3.c swim3: convert to blk-mq 2018-10-16 09:49:36 -06:00
swim_asm.S
swim.c swim: convert to blk-mq 2018-10-16 09:49:18 -06:00
sx8.c sx8: switch to the generic DMA API 2018-10-18 15:14:45 -06:00
umem.c umem: switch to the generic DMA API 2018-10-18 15:14:47 -06:00
umem.h
virtio_blk.c virtio-blk: modernize sysfs attribute creation 2018-09-28 08:30:33 -06:00
xen-blkfront.c xen/blkfront: avoid NULL blkfront_info dereference on device removal 2018-10-25 11:17:39 -06:00
xsysace.c xsysace: convert to blk-mq 2018-10-15 20:08:24 -06:00
z2ram.c powerpc updates for 4.20 2018-10-26 14:36:21 -07:00