Re: 4.1-rc2 dm-multipath-mq kernel warning

[Mike Snitzer <snitzer@redhat.com>]

On Thu, May 28 2015 at  4:19am -0400,
Bart Van Assche <bart.vanassche@sandisk.com> wrote:

> On 05/28/15 00:37, Mike Snitzer wrote:
> >FYI, I've staged a variant patch for 4.1 that is simpler; along with the
> >various fixes I've picked up from Junichi and the leak fix I emailed
> >earlier.  They are now in linux-next and available in this 'dm-4.1'
> >specific branch (based on 4.1-rc5):
> >https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-4.1
> >
> >Please try and let me know if your test works.
> 
> No data corruption was reported this time but a very large number of
> memory leaks were reported by kmemleak. The initiator system ran out
> of memory after some time due to these leaks. Here is an example of
> a leak reported by kmemleak:
> 
> unreferenced object 0xffff8800a39fc1a8 (size 96):
>    comm "srp_daemon", pid 2116, jiffies 4294955508 (age 137.600s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<ffffffff81600029>] kmemleak_alloc+0x49/0xb0
>      [<ffffffff81167d19>] kmem_cache_alloc_node+0xd9/0x190
>      [<ffffffff81425400>] scsi_init_request+0x20/0x40
>      [<ffffffff812cbb98>] blk_mq_init_rq_map+0x228/0x290
>      [<ffffffff812cbcc6>] blk_mq_alloc_tag_set+0xc6/0x220
>      [<ffffffff81427488>] scsi_mq_setup_tags+0xc8/0xd0
>      [<ffffffff8141e34f>] scsi_add_host_with_dma+0x6f/0x300
>      [<ffffffffa04c62bf>] srp_create_target+0x11cf/0x1600 [ib_srp]
>      [<ffffffff813f9c93>] dev_attr_store+0x13/0x20
>      [<ffffffff81200a33>] sysfs_kf_write+0x43/0x60
>      [<ffffffff811fff8b>] kernfs_fop_write+0x13b/0x1a0
>      [<ffffffff81183e53>] __vfs_write+0x23/0xe0
>      [<ffffffff81184524>] vfs_write+0xa4/0x1b0
>      [<ffffffff811852d4>] SyS_write+0x44/0xb0
>      [<ffffffff81613cdb>] system_call_fastpath+0x16/0x73
>      [<ffffffffffffffff>] 0xffffffffffffffff

I suspect I'm missing some cleanup of the request I got from the
underlying blk-mq device.  I'll have a closer look.

> >I don't have SRP setup otherwise I'd try your reproducer you shared a
> >while ago.  Any chance you're aware of a way to reproduce with LIO (and
> >tcm utils)?
> 
> If I find a way to reproduce this with LIO I'll let you know.

Could you try Junichi's script that he posted today to see if it at
least shows the leak?  I'll do the same but I need to rebuild with
kmemleak enabled, etc.