On 03/06/2017 07:39 AM, Minchan Kim wrote: > On Fri, Mar 03, 2017 at 05:13:54PM +0530, Anshuman Khandual wrote: >> On 03/02/2017 12:09 PM, Minchan Kim wrote: >>> try_to_munlock returns SWAP_MLOCK if the one of VMAs mapped >>> the page has VM_LOCKED flag. In that time, VM set PG_mlocked to >>> the page if the page is not pte-mapped THP which cannot be >>> mlocked, either. >> >> Right. >> >>> >>> With that, __munlock_isolated_page can use PageMlocked to check >>> whether try_to_munlock is successful or not without relying on >>> try_to_munlock's retval. It helps to make ttu/ttuo simple with >>> upcoming patches. >> >> Right. >> >>> >>> Cc: Vlastimil Babka <vbabka@xxxxxxx> >>> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> >>> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> >>> --- >>> include/linux/rmap.h | 2 +- >>> mm/mlock.c | 6 ++---- >>> mm/rmap.c | 16 ++++------------ >>> 3 files changed, 7 insertions(+), 17 deletions(-) >>> >>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >>> index b556eef..1b0cd4c 100644 >>> --- a/include/linux/rmap.h >>> +++ b/include/linux/rmap.h >>> @@ -235,7 +235,7 @@ int page_mkclean(struct page *); >>> * called in munlock()/munmap() path to check for other vmas holding >>> * the page mlocked. >>> */ >>> -int try_to_munlock(struct page *); >>> +void try_to_munlock(struct page *); >>> >>> void remove_migration_ptes(struct page *old, struct page *new, bool locked); >>> >>> diff --git a/mm/mlock.c b/mm/mlock.c >>> index cdbed8a..d34a540 100644 >>> --- a/mm/mlock.c >>> +++ b/mm/mlock.c >>> @@ -122,17 +122,15 @@ static bool __munlock_isolate_lru_page(struct page *page, bool getpage) >>> */ >>> static void __munlock_isolated_page(struct page *page) >>> { >>> - int ret = SWAP_AGAIN; >>> - >>> /* >>> * Optimization: if the page was mapped just once, that's our mapping >>> * and we don't need to check all the other vmas. >>> */ >>> if (page_mapcount(page) > 1) >>> - ret = try_to_munlock(page); >>> + try_to_munlock(page); >>> >>> /* Did try_to_unlock() succeed or punt? */ >>> - if (ret != SWAP_MLOCK) >>> + if (!PageMlocked(page)) >> >> Checks if the page is still mlocked or not. >> >>> count_vm_event(UNEVICTABLE_PGMUNLOCKED); >>> >>> putback_lru_page(page); >>> diff --git a/mm/rmap.c b/mm/rmap.c >>> index 0a48958..61ae694 100644 >>> --- a/mm/rmap.c >>> +++ b/mm/rmap.c >>> @@ -1540,18 +1540,10 @@ static int page_not_mapped(struct page *page) >>> * Called from munlock code. Checks all of the VMAs mapping the page >>> * to make sure nobody else has this page mlocked. The page will be >>> * returned with PG_mlocked cleared if no other vmas have it mlocked. >>> - * >>> - * Return values are: >>> - * >>> - * SWAP_AGAIN - no vma is holding page mlocked, or, >>> - * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem >>> - * SWAP_FAIL - page cannot be located at present >>> - * SWAP_MLOCK - page is now mlocked. >>> */ >>> -int try_to_munlock(struct page *page) >>> -{ >>> - int ret; >>> >>> +void try_to_munlock(struct page *page) >>> +{ >>> struct rmap_walk_control rwc = { >>> .rmap_one = try_to_unmap_one, >>> .arg = (void *)TTU_MUNLOCK, >>> @@ -1561,9 +1553,9 @@ int try_to_munlock(struct page *page) >>> }; >>> >>> VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); >>> + VM_BUG_ON_PAGE(PageMlocked(page), page); >> >> We are calling on the page to see if its mlocked from any of it's >> mapping VMAs. Then it is a possibility that the page is mlocked >> and the above condition is true and we print VM BUG report there. >> The point is if its a valid possibility why we have added the >> above check ? > > If I read code properly, __munlock_isolated_page calls try_to_munlock > always pass the TestClearPageMlocked page to try_to_munlock. Right. > (e.g., munlock_vma_page and __munlock_pagevec) so I thought > try_to_munlock should be called non-PG_mlocked page and try_to_unmap_one > returns PG_mlocked page once it found a VM_LOCKED VMA for a page. > IOW, non-PG_mlocked page is precondition for try_to_munlock. Okay, I have missed that part. Nonetheless this is a separate issue, should be part of a different patch ? Not inside these cleanups. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>