| Message ID | 20240126032608.355899-1-senozhatsky@chromium.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/madvise: don't forget to leave lazy MMU mode in madvise_cold_or_pageout_pte_range() | expand |
On Fri, 26 Jan 2024 12:25:48 +0900 Sergey Senozhatsky <senozhatsky@chromium.org> wrote: > We need to leave lazy MMU mode before unlocking. What might be the userspace-visible effects of this? > Fixes: b2f557a21bc8 ("mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range()" > Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> I'll add a cc:stable. > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -451,6 +451,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > if (++batch_count == SWAP_CLUSTER_MAX) { > batch_count = 0; > if (need_resched()) { > + arch_leave_lazy_mmu_mode(); > pte_unmap_unlock(start_pte, ptl); > cond_resched(); > goto restart;
On (24/01/25 22:53), Andrew Morton wrote: > Date: Thu, 25 Jan 2024 22:53:36 -0800 > From: Andrew Morton <akpm@linux-foundation.org> > To: Sergey Senozhatsky <senozhatsky@chromium.org> > Cc: Jiexun Wang <wangjiexun@tinylab.org>, linux-kernel@vger.kernel.org, > linux-mm@kvack.org > Subject: Re: [PATCH] mm/madvise: don't forget to leave lazy MMU mode in > madvise_cold_or_pageout_pte_range() > Message-Id: <20240125225336.6a444c01d9d9812a23a6890b@linux-foundation.org> > X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) > > On Fri, 26 Jan 2024 12:25:48 +0900 Sergey Senozhatsky <senozhatsky@chromium.org> wrote: > > > We need to leave lazy MMU mode before unlocking. It depends on the arch, as far as I understand it. We can enter lazy MMU mode (on each goto restart) more times than leave it, and, for isntance, on powerpc that means that we can preempt_disable() more times than preempt_enable(). That's how enter/leave lazy MMU mode is implemented there: static inline void arch_enter_lazy_mmu_mode(void) { struct ppc64_tlb_batch *batch; if (radix_enabled()) return; /* * apply_to_page_range can call us this preempt enabled when * operating on kernel page tables. */ preempt_disable(); batch = this_cpu_ptr(&ppc64_tlb_batch); batch->active = 1; } static inline void arch_leave_lazy_mmu_mode(void) { struct ppc64_tlb_batch *batch; if (radix_enabled()) return; batch = this_cpu_ptr(&ppc64_tlb_batch); if (batch->index) __flush_tlb_pending(batch); batch->active = 0; preempt_enable(); } > What might be the userspace-visible effects of this? > > > Fixes: b2f557a21bc8 ("mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range()" > > Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> > > I'll add a cc:stable. Thanks.
diff --git a/mm/madvise.c b/mm/madvise.c index 0f222d464254..127f0c7b69ac 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -451,6 +451,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (++batch_count == SWAP_CLUSTER_MAX) { batch_count = 0; if (need_resched()) { + arch_leave_lazy_mmu_mode(); pte_unmap_unlock(start_pte, ptl); cond_resched(); goto restart;
We need to leave lazy MMU mode before unlocking. Fixes: b2f557a21bc8 ("mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range()") Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> --- mm/madvise.c | 1 + 1 file changed, 1 insertion(+)