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From:   Song Liu <songliubraving@fb.com>
To:     Alexander Shishkin <alexander.shishkin@linux.intel.com>
CC:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Kernel Team <Kernel-team@fb.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] perf/core: fix bad use of igrab in
 kernel/event/core.c
Thread-Topic: [PATCH 2/2] perf/core: fix bad use of igrab in
 kernel/event/core.c
Thread-Index: AQHT1t6nfeADCJH+rUmeeV0pDKTod6QHnlsAgDTjVAA=
Date:   Tue, 22 May 2018 21:56:18 +0000
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 <20180419061710.l6sdq3kvricpyjdu@um.fi.intel.com>
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> On Apr 18, 2018, at 11:17 PM, Alexander Shishkin <alexander.shishkin@linu=
x.intel.com> wrote:
>=20
> On Tue, Apr 17, 2018 at 11:29:07PM -0700, Song Liu wrote:
>> As Miklos reported and suggested:
>>=20
>>  This pattern repeats two times in trace_uprobe.c and in
>>  kernel/events/core.c as well:
>>=20
>>      ret =3D kern_path(filename, LOOKUP_FOLLOW, &path);
>>      if (ret)
>>          goto fail_address_parse;
>>=20
>>      inode =3D igrab(d_inode(path.dentry));
>>      path_put(&path);
>>=20
>>  And it's wrong.  You can only hold a reference to the inode if you
>>  have an active ref to the superblock as well (which is normally
>>  through path.mnt) or holding s_umount.
>=20
> Oops. I must have snatched it from the uprobe code without thinking.
>=20
>>  This way unmounting the containing filesystem while the tracepoint is
>>  active will give you the "VFS: Busy inodes after unmount..." message
>>  and a crash when the inode is finally put.
>>=20
>>  Solution: store path instead of inode.
>>=20
>> This patch fixes the issue in kernel/event/core.c.
>>=20
>> NOTE: Based on my understanding, perf_addr_filter only supports intel_pt=
.
>=20
> Coresight too, but that's probably even further away from what you have.
>=20
>> However, my test system doesn't support address filtering (or I made a
>> mistake?). Therefore, I have NOT tested this patch.
>=20
> Check /sys/devices/intel_pt/caps/num_address_ranges, if it's non-zero,
> it's supported.
>=20
>> Could someone please help test it?
>=20
> Yes:
>=20
> Reviewed-and-tested-by: Alexander Shishkin <alexander.shishkin@linux.inte=
l.com>
>=20
> The subject line needs a little love to be more like other perf commits, =
but
> other than that, looks good.
>=20
> Thanks!

Did this patch ever make into tip/perf/XX trees? If not, what shall I do=20
to move it ahead?

Thanks,
Song