Re: [Regression] mmap with MAP_32BIT randomly fails since 6.1

["Liam R. Howlett" <Liam.Howlett@Oracle.com>]

* Robert Hensing <robert@hercules-ci.com> [230511 21:02]:
> It appears that commit 58c5d0d6d522112577c7eeb71d382ea642ed7be4 causes
> another regression of allocations with MAP_32BIT.
> Reverting it fixes the reproducer from
> https://lore.kernel.org/linux-mm/cb8dc31a-fef2-1d09-f133-e9f7b9f9e77a@sony.com/
> 
> Do you think this commit is somewhat safe to revert?

No, don't do that.

Add this [1] instead.  The patch is currently in mm-unstable and will
make its way though the normal channels to stable and mainline

[1] https://lore.kernel.org/linux-mm/20230505145829.74574-1-zhangpeng.00@bytedance.com/

Thanks,
Liam

> 
> The following may be superfluous, but adds some context and might help
> someone
> find this thread. It merely confirms to the observation of this
> regression in
> https://lore.kernel.org/linux-mm/e6108286ac025c268964a7ead3aab9899f9bc6e9.camel@spotco.us/
> 
>  From what I can tell it also fixes my own use case, and
> 
>   - The program I maintain,
>     https://github.com/hercules-ci/hercules-ci-agent/issues/514
> 
>   - Another program, also Haskell:
>     https://github.com/aristanetworks/nix-serve-ng/issues/27
> 
>   - An FPGA interface process. I've found them because they list the same
>     commit id on their blog.
>     https://jia.je/software/2023/05/06/linux-regression-vivado-en/
> 
> 
> 
> On 3/2/23 19:43, Liam R. Howlett wrote:
> > * Snild Dolkow <snild@sony.com> [230302 10:33]:
> >> After upgrading a machine from 5.17.4 to 6.1.12 a couple of weeks ago, I
> >> started getting (inconsistent) failures when building Android:
> >> While it claims to be using 0x22 (MAP_PRIVATE | MAP_ANONYMOUS) for the
> >> flags, it really uses 0x40 (MAP_32BIT) as well, as shown by strace:
> >>
> 
> The same applies to the dynamic linker in the GHC Haskell runtime system.
> 
> It also uses MAP_32BIT, in its linker, and reports the error
> 
> ghc: mmap 4096 bytes at (nil): Cannot allocate memory
> 
> 
> I hope this was a somewhat useful contribution to the regressions
> thread. (also hi, I'm new here)
> 
> Cheers,
> 
> Robert Hensing
> 
>