[PATCH 0/1] Partial fix for mm/slub regression (LP #1895109)

[Kleber Souza]

On 10.09.20 12:13, Andrea Righi wrote:
> On Thu, Sep 10, 2020 at 12:04:05PM +0200, Kleber Sacilotto de Souza wrote:
>> [ Impact ]
>> As reported on bug 1894780 (Oops and hang when starting LVM snapshots
>> on 5.4.0-47), some changes applied to focal/linux 5.4.0-45 introduced a
>> regression likely on the mm/slub code. A fix hasn't been identified yet,
>> however, reverting commit "mm/slub: fix a memory leak in
>> sysfs_slab_add()", upstream dde3c6b72a16c2db826f54b2d49bdea26c3534a2,
>> applied to focal/linux as part of v5.4.47 upstream stable release
>> (bug 1884089), seems to improve the situation.
>>
>> [ Fix ]
>> I propose to revert commit "mm/slub: fix a memory leak in
>> sysfs_slab_add()" while we don't find a better fix for it.
>>
>> [ Test Case ]
>> Please see bug 1894780.
> 
> Did the bug reporter (or anyone else able to reproduce the oops) test a
> kernel with this revert? I don't see any feedback about this in
> LP: #1894780.

Hi Andrea,

It was not commented on the bug but the reporter provided the feedback that
the test kernel made the situation better, at least his systems now boot.
But still regressing from -42, so more investigation is needed.

We are still seeing the following errors on dmes:

[   23.553649] kobject_add_internal failed for :a-0000152 with -EEXIST,
don't try to register things with the same name in the same directory.
[   23.567674] device-mapper: table: 253:6: snapshot: Failed to read
snapshot metadata

Thanks,
Kleber 

> 
> Thanks,
> -Andrea
> 
>>
>> [ Regression potential ]
>> The commit being reverted fixes a memory leak from a 2015 commit, so
>> the chances of reverting it introducing more regressions is low.
>> However, if it does we can expect issues on the sysfs slab code
>> during memory allocations.
>>
>> Kleber Sacilotto de Souza (1):
>>   UBUNTU: SAUCE: Revert "mm/slub: fix a memory leak in sysfs_slab_add()"
>>
>>  mm/slub.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> -- 
>> 2.25.1
>>
>>
>> -- 
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