"Kirill A. Shutemov" <[email protected]> writes: > On Tue, Mar 03, 2015 at 06:51:11PM +0530, Aneesh Kumar K.V wrote: >> 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 ?. > > The patchset changes this. Have you read the cover letter? >
Ok got that. Thanks, -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/
