Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 22 Sep 2020 13:48:40 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 4/5] mm: Do early cow for pinned pages during fork() for ptes |
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On 09/21, Peter Xu wrote: > > @@ -859,6 +989,25 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm, > spin_needbreak(src_ptl) || spin_needbreak(dst_ptl)) > break; > } > + > + if (unlikely(data.cow_new_page)) { > + /* > + * If cow_new_page set, we must be at the 2nd round of > + * a previous COPY_MM_BREAK_COW. Try to arm the new > + * page now. Note that in all cases page_break_cow() > + * will properly release the objects in copy_mm_data. > + */ > + WARN_ON_ONCE(copy_ret != COPY_MM_BREAK_COW); > + if (pte_install_copied_page(dst_mm, new, src_pte, > + dst_pte, addr, rss, > + &data)) { > + /* We installed the pte successfully; move on */ > + progress++; > + continue;
I'm afraid I misread this patch too ;)
But it seems to me in this case the main loop can really "leak" COPY_MM_BREAK_COW. Suppose the the next 31 pte's are pte_none() and need_resched() is true.
No?
Oleg.
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