On 05/28/15 16:07, Mike Snitzer wrote:
On Thu, May 28 2015 at 9:10P -0400,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
On Thu, May 28 2015 at 4:19am -0400,
Bart Van Assche <bart.vanassche@xxxxxxxxxxx> 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.
BTW, your test was with the dm-4.1 branch right?
The above kmemleak trace clearly speaks to dm-mpath's ->clone_and_map_rq
having allocated the underlying scsi-mq request. So it'll later require
a call to dm-mpath's ->release_clone_rq to free the associated memory --
which happens in dm.c:free_rq_clone().
But I'm not yet seeing where we'd be missing a required call to
free_rq_clone() in the DM core error paths. You can try this patch to
see if you hit the WARN_ON but I highly doubt you would.. similarly the
clone request shouldn't ever be allocated (nor tio->clone initialized)
in the REQUEUE case:
Hello Mike,
This occurred with the dm-4.1 branch merged with the for-4.2 IB branch.
The leak was reported for regular I/O and before I started to trigger
path failures. I had a look myself at how the sense_buffer pointer is
manipulated by the scsi-mq code but could not find anything that is
wrong. So the next I did was to repeat my test with kmemleak disabled.
During this test the number of kmalloc-96 objects in /proc/slabinfo
remained constant. So I probably have hit a bug in kmemleak. Maybe the
code that clears and restores the sense buffer pointer in
scsi_mq_prep_fn() is confusing kmemleak ? Sorry for the noise.
Bart.
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