Hi Sergey, On Thu, Mar 09, 2017 at 01:29:08PM +0900, Sergey Senozhatsky wrote: > Hello Minchan, > > /* I can't https://marc.info/?l=linux-kernel&m=148886631303107 thread > in my mail box for some reason so the Reply-To message-id may be wrong. */ > > > > commit "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" > (mmotm fd07630cbf59bead90046dd3e5cfd891e58e6987) > > > if (VM_WARN_ON_ONCE(PageSwapBacked(page) != > PageSwapCache(page))) { > ... > } > > > does not compile on !CONFIG_DEBUG_VM configs, because VM_WARN_ONCE() is > > #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) > > > > In file included from ./include/linux/mmdebug.h:4:0, > from ./include/linux/mm.h:8, > from mm/rmap.c:48: > mm/rmap.c: In function ‘try_to_unmap_one’: > ./include/linux/bug.h:45:33: error: void value not ignored as it ought to be > #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) > ^ > ./include/linux/mmdebug.h:49:31: note: in expansion of macro > ‘BUILD_BUG_ON_INVALID’ > #define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond) > ^~~~~~~~~~~~~~~~~~~~ > mm/rmap.c:1416:8: note: in expansion of macro ‘VM_WARN_ON_ONCE’ > if (VM_WARN_ON_ONCE(PageSwapBacked(page) != > ^~~~~~~~~~~~~~~ > > -ss >
Thanks for the report, Sergey! If others are not against, I want to go this. >From 38b10e560d066c2cef8f9d028e14008cefdaa3e0 Mon Sep 17 00:00:00 2001 From: Minchan Kim <[email protected]> Date: Thu, 9 Mar 2017 14:58:23 +0900 Subject: [PATCH] mm: do not use VM_WARN_ON_ONCE as if condition Sergey reported VM_WARN_ON_ONCE returns void with !CONFIG_DEBUG_VM so we cannot use it as if's condition unlike WARN_ON. This patch fixes it. Signed-off-by: Minchan Kim <[email protected]> --- mm/rmap.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 1d82057144ba..7d24bb93445b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1413,12 +1413,11 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, * Store the swap location in the pte. * See handle_pte_fault() ... */ - if (VM_WARN_ON_ONCE(PageSwapBacked(page) != - PageSwapCache(page))) { + if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) { + WARN_ON_ONCE(1); ret = SWAP_FAIL; page_vma_mapped_walk_done(&pvmw); break; - } /* MADV_FREE page check */ -- 2.7.4
