ACK: [SRU] [Artful] [PATCH 1/1] vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems

[Kleber Souza]

On 03/01/18 07:13, Kai-Heng Feng wrote:
> From: Michal Hocko <mhocko at suse.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1742316
> 
> Kai Heng Feng has noticed that BUG_ON(PageHighMem(pg)) triggers in
> drivers/media/common/saa7146/saa7146_core.c since 19809c2da28a ("mm,
> vmalloc: use __GFP_HIGHMEM implicitly").
> 
> saa7146_vmalloc_build_pgtable uses vmalloc_32 and it is reasonable to
> expect that the resulting page is not in highmem.  The above commit
> aimed to add __GFP_HIGHMEM only for those requests which do not specify
> any zone modifier gfp flag.  vmalloc_32 relies on GFP_VMALLOC32 which
> should do the right thing.  Except it has been missed that GFP_VMALLOC32
> is an alias for GFP_KERNEL on 32b architectures.  Thanks to Matthew to
> notice this.
> 
> Fix the problem by unconditionally setting GFP_DMA32 in GFP_VMALLOC32
> for !64b arches (as a bailout).  This should do the right thing and use
> ZONE_NORMAL which should be always below 4G on 32b systems.
> 
> Debugged by Matthew Wilcox.
> 
> [akpm at linux-foundation.org: coding-style fixes]
> Link: http://lkml.kernel.org/r/20180212095019.GX21609@dhcp22.suse.cz
> Fixes: 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitly”)
> Signed-off-by: Michal Hocko <mhocko at suse.com>
> Reported-by: Kai Heng Feng <kai.heng.feng at canonical.com>
> Cc: Matthew Wilcox <willy at infradead.org>
> Cc: Laura Abbott <labbott at redhat.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (cherry picked from commit 698d0831ba87b92ae10b15e8203cfd59f5a59a35)
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
> ---
>  mm/vmalloc.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ceacc6e01904..07b4deef6faa 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1945,11 +1945,15 @@ void *vmalloc_exec(unsigned long size)
>  }
>  
>  #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
> -#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
> +#define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL)
>  #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
> -#define GFP_VMALLOC32 GFP_DMA | GFP_KERNEL
> +#define GFP_VMALLOC32 (GFP_DMA | GFP_KERNEL)
>  #else
> -#define GFP_VMALLOC32 GFP_KERNEL
> +/*
> + * 64b systems should always have either DMA or DMA32 zones. For others
> + * GFP_DMA32 should do the right thing and use the normal zone.
> + */
> +#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
>  #endif
>  
>  /**
> 

Good test results, also backported for the stable trees.

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>