* "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error
@ 2017-03-09 4:29 Sergey Senozhatsky
2017-03-09 6:02 ` Minchan Kim
0 siblings, 1 reply; 6+ messages in thread
From: Sergey Senozhatsky @ 2017-03-09 4:29 UTC (permalink / raw)
To: Minchan Kim
Cc: Johannes Weiner, Michal Hocko, Andrew Morton, linux-kernel,
linux-mm
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 a??try_to_unmap_onea??:
./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 a??BUILD_BUG_ON_INVALIDa??
#define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
^~~~~~~~~~~~~~~~~~~~
mm/rmap.c:1416:8: note: in expansion of macro a??VM_WARN_ON_ONCEa??
if (VM_WARN_ON_ONCE(PageSwapBacked(page) !=
^~~~~~~~~~~~~~~
-ss
--
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error 2017-03-09 4:29 "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error Sergey Senozhatsky @ 2017-03-09 6:02 ` Minchan Kim 2017-03-09 8:50 ` Michal Hocko 2017-03-09 21:27 ` Andrew Morton 0 siblings, 2 replies; 6+ messages in thread From: Minchan Kim @ 2017-03-09 6:02 UTC (permalink / raw) To: Sergey Senozhatsky, Andrew Morton Cc: Johannes Weiner, Michal Hocko, linux-kernel, linux-mm 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 a??try_to_unmap_onea??: > ./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 a??BUILD_BUG_ON_INVALIDa?? > #define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond) > ^~~~~~~~~~~~~~~~~~~~ > mm/rmap.c:1416:8: note: in expansion of macro a??VM_WARN_ON_ONCEa?? > if (VM_WARN_ON_ONCE(PageSwapBacked(page) != > ^~~~~~~~~~~~~~~ > > -ss > Thanks for the report, Sergey! If others are not against, I want to go this. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error 2017-03-09 6:02 ` Minchan Kim @ 2017-03-09 8:50 ` Michal Hocko 2017-03-09 21:27 ` Andrew Morton 1 sibling, 0 replies; 6+ messages in thread From: Michal Hocko @ 2017-03-09 8:50 UTC (permalink / raw) To: Minchan Kim Cc: Sergey Senozhatsky, Andrew Morton, Johannes Weiner, linux-kernel, linux-mm On Thu 09-03-17 15:02:26, Minchan Kim wrote: [...] > >From 38b10e560d066c2cef8f9d028e14008cefdaa3e0 Mon Sep 17 00:00:00 2001 > From: Minchan Kim <minchan@kernel.org> > 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. I would swear I've seen WARN_ON_ONCE there when looking at the previous patch! Btw. could have simply s@VM_@@ > This patch fixes it. > > Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> > --- > 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 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error 2017-03-09 6:02 ` Minchan Kim 2017-03-09 8:50 ` Michal Hocko @ 2017-03-09 21:27 ` Andrew Morton 2017-03-10 0:45 ` Minchan Kim 1 sibling, 1 reply; 6+ messages in thread From: Andrew Morton @ 2017-03-09 21:27 UTC (permalink / raw) To: Minchan Kim Cc: Sergey Senozhatsky, Johannes Weiner, Michal Hocko, linux-kernel, linux-mm On Thu, 9 Mar 2017 15:02:26 +0900 Minchan Kim <minchan@kernel.org> wrote: > Sergey reported VM_WARN_ON_ONCE returns void with !CONFIG_DEBUG_VM > so we cannot use it as if's condition unlike WARN_ON. Can we instead fix VM_WARN_ON_ONCE()? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error 2017-03-09 21:27 ` Andrew Morton @ 2017-03-10 0:45 ` Minchan Kim 2017-03-10 9:31 ` Vlastimil Babka 0 siblings, 1 reply; 6+ messages in thread From: Minchan Kim @ 2017-03-10 0:45 UTC (permalink / raw) To: Andrew Morton Cc: Sergey Senozhatsky, Johannes Weiner, Michal Hocko, linux-kernel, linux-mm Hi Andrew, On Thu, Mar 09, 2017 at 01:27:06PM -0800, Andrew Morton wrote: > On Thu, 9 Mar 2017 15:02:26 +0900 Minchan Kim <minchan@kernel.org> wrote: > > > Sergey reported VM_WARN_ON_ONCE returns void with !CONFIG_DEBUG_VM > > so we cannot use it as if's condition unlike WARN_ON. > > Can we instead fix VM_WARN_ON_ONCE()? I thought the direction but the reason to decide WARN_ON_ONCE in this case is losing of benefit with using CONFIG_DEBU_VM if we go that way. I think the benefit with VM_WARN_ON friends is that it should be completely out from the binary in !CONFIG_DEBUG_VM. However, if we fix VM_WARN_ON like WARN_ON to !!condition, at least, compiler should generate condition check and return so it's not what CONFIG_DEBUG_VM want, IMHO. However, if guys believe it's okay to add some instructions to debug VM although we disable CONFIG_DEBUG_VM, we can go that way. It's a just policy matter. ;-) Anyway, Even though we fix VM_WARN_ON_ONCE, in my case, WARN_ON_ONCE is better because we should do !!condition regardless of CONFIG_DEBUG_VM and if so, WARN_ON is more wide coverage than VM_WARN_ON which only works with CONFIG_DEBUG_VM. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error 2017-03-10 0:45 ` Minchan Kim @ 2017-03-10 9:31 ` Vlastimil Babka 0 siblings, 0 replies; 6+ messages in thread From: Vlastimil Babka @ 2017-03-10 9:31 UTC (permalink / raw) To: Minchan Kim, Andrew Morton Cc: Sergey Senozhatsky, Johannes Weiner, Michal Hocko, linux-kernel, linux-mm On 03/10/2017 01:45 AM, Minchan Kim wrote: > Hi Andrew, > > On Thu, Mar 09, 2017 at 01:27:06PM -0800, Andrew Morton wrote: >> On Thu, 9 Mar 2017 15:02:26 +0900 Minchan Kim <minchan@kernel.org> wrote: >> >>> Sergey reported VM_WARN_ON_ONCE returns void with !CONFIG_DEBUG_VM >>> so we cannot use it as if's condition unlike WARN_ON. >> >> Can we instead fix VM_WARN_ON_ONCE()? > > I thought the direction but the reason to decide WARN_ON_ONCE in this case > is losing of benefit with using CONFIG_DEBU_VM if we go that way. > > I think the benefit with VM_WARN_ON friends is that it should be completely > out from the binary in !CONFIG_DEBUG_VM. However, if we fix VM_WARN_ON > like WARN_ON to !!condition, at least, compiler should generate condition > check and return so it's not what CONFIG_DEBUG_VM want, IMHO. > However, if guys believe it's okay to add some instructions to debug VM > although we disable CONFIG_DEBUG_VM, we can go that way. > It's a just policy matter. ;-) > > Anyway, Even though we fix VM_WARN_ON_ONCE, in my case, WARN_ON_ONCE is > better because we should do !!condition regardless of CONFIG_DEBUG_VM > and if so, WARN_ON is more wide coverage than VM_WARN_ON which only works > with CONFIG_DEBUG_VM. Agreed. WARN_ON...() can work that way as one can't disable them (AFAIK), but VM_* variants are optional for overhead reasons. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-03-10 9:31 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2017-03-09 4:29 "mm: fix lazyfree BUG_ON check in try_to_unmap_one()" build error Sergey Senozhatsky 2017-03-09 6:02 ` Minchan Kim 2017-03-09 8:50 ` Michal Hocko 2017-03-09 21:27 ` Andrew Morton 2017-03-10 0:45 ` Minchan Kim 2017-03-10 9:31 ` Vlastimil Babka
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