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Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into node_page_state

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On Thursday, June 23, 2016 11:41:24 AM CEST Mel Gorman wrote:
> On Thu, Jun 23, 2016 at 12:05:17PM +0200, Arnd Bergmann wrote:
> > I see some new warnings from a recent mm change:
> > 
> > mm/filemap.c: In function '__delete_from_page_cache':
> > include/linux/vmstat.h:116:2: error: array subscript is above array bounds [-Werror=array-bounds]
> >   atomic_long_add(x, &zone->vm_stat[item]);
> >   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > include/linux/vmstat.h:116:35: error: array subscript is above array bounds [-Werror=array-bounds]
> >   atomic_long_add(x, &zone->vm_stat[item]);
> >                       ~~~~~~~~~~~~~^~~~~~
> > include/linux/vmstat.h:116:35: error: array subscript is above array bounds [-Werror=array-bounds]
> > include/linux/vmstat.h:117:2: error: array subscript is above array bounds [-Werror=array-bounds]
> > 
> > Looking deeper into it, I find that we pass the wrong enum
> > into some functions after the type for the symbol has changed.
> > 
> > This changes the code to use the other function for those that
> > are using the incorrect type. I've done this blindly just going
> > by warnings I got from a debug patch I did for this, so it's likely
> > that some cases are more subtle and need another change, so please
> > treat this as a bug-report rather than a patch for applying.
> > 
> 
> I have an alternative fix for this in a private tree. For now, I've asked
> Andrew to withdraw the series entirely as there are non-trivial collisions
> with OOM detection rework and huge page support for tmpfs.  It'll be easier
> and safer to resolve this outside of mmotm as it'll require a full round
> of testing which takes 3-4 days.

Ok. I've done a new version of my debug patch now, will follow up here
so you can do some testing on top of that as well if you like. We probably
don't want to apply my patch for the type checking, but you might find it
useful for your own testing.

	Arnd

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[RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into node_page_state Arnd Bergmann <arnd@arndb.de> - 2016-06-23 12:10 +0200
  Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into  node_page_state Mel Gorman <mgorman@techsingularity.net> - 2016-06-23 12:50 +0200
    Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into node_page_state Arnd Bergmann <arnd@arndb.de> - 2016-06-23 15:20 +0200
      Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into  node_page_state Mel Gorman <mgorman@techsingularity.net> - 2016-06-23 16:00 +0200
        Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into node_page_state Arnd Bergmann <arnd@arndb.de> - 2016-06-23 18:00 +0200
          Re: [RFC, DEBUGGING 1/2] mm: pass NR_FILE_PAGES/NR_SHMEM into  node_page_state Mel Gorman <mgorman@techsingularity.net> - 2016-06-23 18:40 +0200

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