[DragonFlyBSD - Bug #2756] Hit kernel panic while running hammer show cmd

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Sat Jan 3 07:42:45 PST 2015

Issue #2756 has been updated by tuxillo.


I can't reproduce it:

1) In a vkernel (though it runs DragonFly 4.1) with a normal and a full filesystem:

vk01# df -h
Filesystem   Size   Used  Avail Capacity  Mounted on
VKROOT        19G   3.6G    16G    19%    /
devfs        1.0K   1.0K     0B   100%    /dev
TEST         3.2G   3.2G  -7.8M   100%    /mnt
vk01# hammer -f /dev/vkd0s1a show > /dev/null
vk01# hammer -f /dev/vkd1s1d show > /dev/null

2) In a VMWare VM (DragonFly 4.0) with a bigger filesystem than  yours:

nas# df -h /
Filesystem   Size   Used  Avail Capacity  Mounted on
ROOT         545G   417G   127G    77%    /
nas# hammer -f /dev/da0s1d show > /dev/null

Do you have any messages in dmesg? Which disk driver are you using in VBox?

Antonio Huete

Bug #2756: Hit kernel panic while running hammer show cmd

* Author: tkusumi
* Status: New
* Priority: High
* Assignee: 
* Category: Kernel
* Target version: 4.0.x
Hit kernel panic while running hammer show cmd. All I did was

# uname -r
# hammer -f /dev/serno/xxxxxxxx.s1d show > show.out

where /dev/serno/xxxxxxxx.s1d is a volume for / hammerfs with enough space left. It's running as a virtualbox guest on x86_64. It happens whenever the size of show.out gets around 250MB.

# df -h
Filesystem                           Size   Used  Avail Capacity  Mounted on
ROOT                                  74G   8.2G    66G    11%    /

x/i says it died at movl at dscheck+0x8b (ffffffff80618025)
ffffffff80618025:       44 8b 7b 0c             mov    0xc(%rbx),%r15d
ffffffff80618029:       44 3b 7d b8             cmp    -0x48(%rbp),%r15d
ffffffff8061802d:       77 28                   ja     ffffffff80618057 <dscheck+0xbd>

dscheck() was called as a sequence of btree lookup by hammer show. hammer_vop_strategy_read() -> hammer_ip_first() -> hammer_btree_lookup() -> btree_search() -> hammer_cursor_down() -> hammer_get_node() -> hammer_load_node() -> hammer_get_buffer() -> hammer_load_buffer() -> hammer_io_read() -> hammer_cluster_read() -> ... (failed to catch any further)

I saw disas of /boot/kernel/kernel and this movl seems to be null pointer dereference of *ssp at
if (slice >= ssp->dss_nslices)
of the following.

> struct bio *
> dscheck(cdev_t dev, struct bio *bio, struct diskslices *ssp)
> {
>         struct buf *bp = bio->bio_buf;
>         struct bio *nbio;
>         disklabel_t lp;
>         disklabel_ops_t ops;
>         long nsec;
>         u_int64_t secno;
>         u_int64_t endsecno;
>         u_int64_t slicerel_secno;
>         struct diskslice *sp;
>         u_int32_t part;
>         u_int32_t slice;
>         int shift;
>         int mask;
>         slice = dkslice(dev);
>         part  = dkpart(dev);
>         if (bio->bio_offset < 0) {
>                 kprintf("dscheck(%s): negative bio_offset %lld\n",
>                         devtoname(dev), (long long)bio->bio_offset);
>                 goto bad;
>         }
>         if (slice >= ssp->dss_nslices) {
>                 kprintf("dscheck(%s): slice too large %d/%d\n",
>                         devtoname(dev), slice, ssp->dss_nslices);
>                 goto bad;
>         }

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