Rik van Riel <[email protected]> writes: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 02/12/2015 02:55 PM, Rik van Riel wrote: >> On 02/12/2015 11:18 AM, Kirill A. Shutemov wrote: > >>> @@ -490,6 +493,7 @@ extern int >>> wait_on_page_bit_killable_timeout(struct page *page, >> >>> static inline int wait_on_page_locked_killable(struct page *page) >>> { + page = compound_head(page); if (PageLocked(page)) return >>> wait_on_page_bit_killable(page, PG_locked); return 0; @@ -510,6 >>> +514,7 @@ static inline void wake_up_page(struct page *page, int >>> bit) */ static inline void wait_on_page_locked(struct page *page) >>> { + page = compound_head(page); if (PageLocked(page)) >>> wait_on_page_bit(page, PG_locked); } >> >> These are all atomic operations. >> >> This may be a stupid question with the answer lurking somewhere in >> the other patches, but how do you ensure you operate on the right >> page lock during a THP collapse or split? > > Kirill answered that question on IRC. > > The VM takes a refcount on a page before attempting to take a page > lock, which prevents the THP code from doing anything with the > page. In other words, while we have a refcount on the page, we > will dereference the same page lock.
Can we explain this more ? Don't we allow a thp split to happen even if we have page refcount ?. -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
