On 12/07/2016 12:08 PM, Vladimir Davydov wrote: > Hello, > > On Mon, Dec 05, 2016 at 09:55:10PM -0800, Hugh Dickins wrote: >> Rechecking PageLRU() after get_page_unless_zero() may have value, but >> holding zone_lru_lock around that serves no useful purpose: delete it. > > IIRC this lock/unlock was added on purpose, by request from Minchan. It > serves as a barrier that guarantees that all page fields (specifically > ->mapping in case of anonymous pages) have been properly initialized by > the time we pass it to rmap_walk(). Here's a reference to the thread > where this problem was discussed: > > http://lkml.kernel.org/r/<20150430082531.GD21771@blaptop> Um OK, but then there should have been a comment explaining why the lock is there :/ Vlastimil >> >> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> >> --- >> >> mm/page_idle.c | 4 ---- >> 1 file changed, 4 deletions(-) >> >> --- 4.9-rc8/mm/page_idle.c 2016-10-02 16:24:33.000000000 -0700 >> +++ linux/mm/page_idle.c 2016-12-05 19:44:32.646625435 -0800 >> @@ -30,7 +30,6 @@ >> static struct page *page_idle_get_page(unsigned long pfn) >> { >> struct page *page; >> - struct zone *zone; >> >> if (!pfn_valid(pfn)) >> return NULL; >> @@ -40,13 +39,10 @@ static struct page *page_idle_get_page(u >> !get_page_unless_zero(page)) >> return NULL; >> >> - zone = page_zone(page); >> - spin_lock_irq(zone_lru_lock(zone)); >> if (unlikely(!PageLRU(page))) { >> put_page(page); >> page = NULL; >> } >> - spin_unlock_irq(zone_lru_lock(zone)); >> return page; >> } >> > > -- > 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> > -- 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>