linux-kernel - Re: [PATCH 1/2] maple_tree: Fix mas_skip

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Date:   Fri, 3 Mar 2023 09:51:15 +0100
From:   Snild Dolkow <snild@...y.com>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Stable@...r.kernel.org
Subject: Re: [PATCH 1/2] maple_tree: Fix mas_skip_node() end slot detection

Thanks, this is a significant improvement. Applying it on top of v6.1.12 
allows my reproducer to pass most of the time (running as init in qemu).

Unfortunately, it's still failing around 10% of the time:
> $ for x in $(seq 100); do qemu-system-x86_64 -nographic -no-reboot -append 'console=ttyS0 panic=-1' -kernel arch/x86/boot/bzImage -initrd initrd/initrd.gz; done | tee qemu.log
> [...] > $ egrep -o 'Failed|Success' qemu.log | sort | uniq -c
>      11 Failed
>      89 Success

The failures now happen later, around 25 MiB:
> $ grep Failed qemu.log
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=1050  errno=12 total_leaks=29081600 (27 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=332  errno=12 total_leaks=23199744 (22 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=838  errno=12 total_leaks=27344896 (26 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=282  errno=12 total_leaks=22790144 (21 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=695  errno=12 total_leaks=26173440 (24 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=1064  errno=12 total_leaks=29196288 (27 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=608  errno=12 total_leaks=25460736 (24 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=443  errno=12 total_leaks=24109056 (22 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=549  errno=12 total_leaks=24977408 (23 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=630  errno=12 total_leaks=25640960 (24 MiB)
> Failed. m=0xffffffffffffffff size=8192 (1<<13) i=820  errno=12 total_leaks=27197440 (25 MiB)


Just to make sure, I went back to e15e06a8 and ran the same loop.
> $ egrep -o 'Failed|Success' qemu.log | sort | uniq -c
>     100 Success

And with the patches applied on top of master (ee3f96b1):
> $ egrep -o 'Failed|Success' qemu.log | sort | uniq -c
>      10 Failed
>      90 Success

//Snild