Daniel Axtens dja@axtens.net writes:
Lukas Bulwahn lukas.bulwahn@gmail.com writes:
Commit 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK") selects the non-existing config ARCH_ENABLE_PMD_SPLIT_PTLOCK in ./arch/powerpc/platforms/Kconfig.cputype, but clearly it intends to select ARCH_ENABLE_SPLIT_PMD_PTLOCK here (notice the word swapping!), as this commit does select that for all other architectures.
Rectify selection to ARCH_ENABLE_SPLIT_PMD_PTLOCK instead.
Yikes, yes, 66f24fa766e3 does seem to have got that wrong. It looks like that went into 5.13.
I think we want to specifically target this for stable so that we don't lose the perfomance and scalability benefits of split pmd ptlocks:
Cc: stable@vger.kernel.org # v5.13+
(I don't think you need to do another revision for this, I think mpe could add it when merging.)
Yeah. I rewrote the change log a bit to make it clear this is a bug fix, not a harmless cleanup.
cheers
powerpc: Re-enable ARCH_ENABLE_SPLIT_PMD_PTLOCK
Commit 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK") broke PMD split page table lock for powerpc.
It selects the non-existent config ARCH_ENABLE_PMD_SPLIT_PTLOCK in arch/powerpc/platforms/Kconfig.cputype, but clearly intended to select ARCH_ENABLE_SPLIT_PMD_PTLOCK (notice the word swapping!), as that commit did for all other architectures.
Fix it by selecting the correct symbol ARCH_ENABLE_SPLIT_PMD_PTLOCK.
Fixes: 66f24fa766e3 ("mm: drop redundant ARCH_ENABLE_SPLIT_PMD_PTLOCK") Cc: stable@vger.kernel.org # v5.13+ Signed-off-by: Lukas Bulwahn lukas.bulwahn@gmail.com Reviewed-by: Daniel Axtens dja@axtens.net [mpe: Reword change log to make it clear this is a bug fix] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20210819113954.17515-3-lukas.bulwahn@gmail.com