RE: mm: fix BUG in __split_huge_page_pmd

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hugh Dickins wrote:
> Occasionally we hit the BUG_ON(pmd_trans_huge(*pmd)) at the end of
> __split_huge_page_pmd(): seen when doing madvise(,,MADV_DONTNEED).
> 
> It's invalid: we don't always have down_write of mmap_sem there:
> a racing do_huge_pmd_wp_page() might have copied-on-write to another
> huge page before our split_huge_page() got the anon_vma lock.
> 
> Forget the BUG_ON, just go back and try again if this happens.
>     
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Looks reasonable to me.

Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

madvise(MADV_DONTNEED) was aproblematic with THP before. Is a big win having
mmap_sem taken on read rather than on write for it?

-- 
 Kirill A. Shutemov

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>




[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]