On Tue, May 12, 2020 at 8:09 PM Weiping Zhang <zwp10758@xxxxxxxxx> wrote:
>
> On Tue, May 12, 2020 at 9:31 AM Bart Van Assche <bvanassche@xxxxxxx> wrote:
> >
> > On 2020-05-07 06:03, Weiping Zhang wrote:
> > > This series mainly fix the kernel panic when increase hardware queue,
> > > and also fix some other misc issue.
> >
> > Does this patch series survive blktests? I'm asking this because
> > blktests triggers the crash shown below for Jens' block-for-next branch.
> > I think this report is the result of a recent change.
> >
> > run blktests block/030
> >
> > null_blk: module loaded
> > Increasing nr_hw_queues to 8 fails, fallback to 1
> > ==================================================================
> > BUG: KASAN: null-ptr-deref in blk_mq_map_swqueue+0x2f2/0x830
> > Read of size 8 at addr 0000000000000128 by task nproc/8541
> >
> > CPU: 5 PID: 8541 Comm: nproc Not tainted 5.7.0-rc4-dbg+ #3
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
> > Call Trace:
> > dump_stack+0xa5/0xe6
> > __kasan_report.cold+0x65/0xbb
> > kasan_report+0x45/0x60
> > check_memory_region+0x15e/0x1c0
> > __kasan_check_read+0x15/0x20
> > blk_mq_map_swqueue+0x2f2/0x830
> > __blk_mq_update_nr_hw_queues+0x3df/0x690
> > blk_mq_update_nr_hw_queues+0x32/0x50
> > nullb_device_submit_queues_store+0xde/0x160 [null_blk]
> > configfs_write_file+0x1c4/0x250 [configfs]
> > __vfs_write+0x4c/0x90
> > vfs_write+0x14b/0x2d0
> > ksys_write+0xdd/0x180
> > __x64_sys_write+0x47/0x50
> > do_syscall_64+0x6f/0x310
> > entry_SYSCALL_64_after_hwframe+0x49/0xb3
> >
> > Thanks,
> >
>
> Hi Bart,
>
> I don't test block/030, since I don't pull blktest very often.
>
> It's a different problem,
> because the mapping cann't be reset when do fallback, so the
> cpu[>=1] will point to a hctx(!=0).
>
> it should be fixed by:
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index bc34d6b572b6..d82cefb0474f 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -3365,8 +3365,8 @@ static void __blk_mq_update_nr_hw_queues(struct
> blk_mq_tag_set *set,
> goto reregister;
>
> set->nr_hw_queues = nr_hw_queues;
> - blk_mq_update_queue_map(set);
> fallback:
> + blk_mq_update_queue_map(set);
> list_for_each_entry(q, &set->tag_list, tag_set_list) {
> blk_mq_realloc_hw_ctxs(set, q);
> if (q->nr_hw_queues != set->nr_hw_queues) {
And block/030 should also be improved ?
35 # Since older null_blk versions do not allow "submit_queues" to be
36 # modified, check first whether that configs attribute is writeable.
37 # Each iteration of the loop below triggers $(nproc) + 1
38 # null_init_hctx() calls. Since <interval>=$(nproc), all possible
39 # blk_mq_realloc_hw_ctxs() error paths will be triggered. Whether or
40 # not this test succeeds depends on whether or not _check_dmesg()
41 # detects a kernel warning.
42 if { echo "$(<"$sq")" >$sq; } 2>/dev/null; then
43 for ((i = 0; i < 100; i++)); do
44 echo 1 > $sq
45 nproc > $sq # this line output lots
"nproc: write error: Cannot allocate memory"
46 done
47 else
48 SKIP_REASON="Skipping test because $sq cannot be modified"
49 fi
The test result show this test case [failed], actually it [pass],
there is no warning detect
in kernel log, if apply above patch.
block/030 (trigger the blk_mq_realloc_hw_ctxs() error path) [failed]
runtime 1.999s ... 2.115s
--- tests/block/030.out 2020-05-12 10:42:26.345782849 +0800
+++ /data1/zwp/src/blktests/results/nodev/block/030.out.bad
2020-05-12 20:14:59.878915218 +0800
@@ -1 +1,51 @@
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
+nproc: write error: Cannot allocate memory
...
(Run 'diff -u tests/block/030.out
/data1/zwp/src/blktests/results/nodev/block/030.out.bad' to see the
entire diff)
Thanks
Weiping
