Re: [PATCH 0/2] ceph: fix iov_iter issues in ceph_direct_read_write()

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On Tue, May 8, 2018 at 2:47 PM, Luis Henriques <lhenriques@xxxxxxxx> wrote:
> Ilya Dryomov <idryomov@xxxxxxxxx> writes:
>
>> Hi Luis, Jeff,
>>
>> This is an updated version that fixes the problem with pipe buffers.
>> I wasn't able to get "trinity -V /some/dir/in/cephfs -c splice" do it
>> for me, but a simple "overflow the pipe" test now passes.
>>
>> I believe this is ready for merging.  Please take a look.
>
> Ok, I can confirm that I no longer see splice trashing the kernel when
> running trinity.  However, I'm currently investigating a leak reported
> by kmemleak.  It takes a while to trigger (same testcase: splice syscall
> stress with trinity), but I eventually see something like:
>
> unreferenced object 0xffff880061a3b9d8 (size 128):
>   comm "trinity-c0", pid 303, jiffies 4295049336 (age 5361.756s)
>   hex dump (first 32 bytes):
>     89 5a 51 c4 1a 90 82 fa 40 5b 8a 01 00 ea ff ff  .ZQ.....@[......
>     c0 82 93 01 00 ea ff ff 80 71 94 01 00 ea ff ff  .........q......
>   backtrace:
>     [<000000005a0f2bb8>] ceph_read_iter+0xf8e/0x10b0
>     [<00000000a8278adb>] generic_file_splice_read+0x21b/0x320
>     [<000000004fcba43d>] __se_sys_splice+0x914/0x9a0
>     [<00000000276d178b>] do_syscall_64+0xee/0x290
>     [<00000000f883973e>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>     [<00000000eab9257f>] 0xffffffffffffffff
>
> It could be a false positive, not sure yet.  It may not even been
> related with these changes.  I'll let you know what I can find.

128 bytes is 16 page pointers.  I think it's the leak I found when
tracking down that problem with pipes.  Fixed by

  https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/commit/?h=for-linus&id=e76b6312391bdd62e31dc86cb65e478b07b7909e
  https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/commit/?h=for-linus&id=d7760d638b140d53c6390a2fbee9b06460b43e9e

Sorry, I should have added those commits to testing.

Thanks,

                Ilya
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