Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-24 Thread Dmitry Vyukov
On Fri, Mar 24, 2017 at 3:10 PM, Peter Zijlstra wrote: > On Fri, Mar 24, 2017 at 02:50:24PM +0100, Dmitry Vyukov wrote: >> OK, I guess should not have referenced the llvm-linux page. >> So here are reasons on our side that I am ready to vouch: >> >> - clang make it possible

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-24 Thread Peter Zijlstra
On Fri, Mar 24, 2017 at 02:50:24PM +0100, Dmitry Vyukov wrote: > OK, I guess should not have referenced the llvm-linux page. > So here are reasons on our side that I am ready to vouch: > > - clang make it possible to implement KMSAN (dynamic detection of > uses of uninit memory) How does GCC

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-24 Thread Peter Zijlstra
On Fri, Mar 24, 2017 at 02:47:15PM +0100, Dmitry Vyukov wrote: > > Seriously, you should have taken the hack the first time that this > > needs to be fixed. Just because this is a fairly uncommon construct > > in the kernel doesn't mean it is not in userspace. > > There is a reason why it is

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-24 Thread Dmitry Vyukov
On Fri, Mar 17, 2017 at 8:29 PM, Peter Zijlstra wrote: > On Fri, Mar 17, 2017 at 08:26:42PM +0100, Peter Zijlstra wrote: >> On Fri, Mar 17, 2017 at 08:05:16PM +0100, Dmitry Vyukov wrote: >> > You can also find some reasons in the Why section of LLVM-Linux project: >> >

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-24 Thread Dmitry Vyukov
On Fri, Mar 17, 2017 at 9:04 PM, wrote: > On March 17, 2017 12:27:46 PM PDT, Peter Zijlstra > wrote: >>On Fri, Mar 17, 2017 at 11:52:01AM -0700, Michael Davidson wrote: >>> On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra >> wrote: >>>

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Fengguang Wu
Hi Dmitry, On Fri, Mar 17, 2017 at 08:05:16PM +0100, Dmitry Vyukov wrote: On Fri, Mar 17, 2017 at 7:57 PM, Borislav Petkov wrote: On Fri, Mar 17, 2017 at 07:47:33PM +0100, Dmitry Vyukov wrote: This problem is more general and is not specific to clang. It equally applies to

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread hpa
On March 17, 2017 12:27:46 PM PDT, Peter Zijlstra wrote: >On Fri, Mar 17, 2017 at 11:52:01AM -0700, Michael Davidson wrote: >> On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra > wrote: >> > >> > Be that as it may; what you construct above is disgusting.

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Peter Zijlstra
On Fri, Mar 17, 2017 at 08:05:16PM +0100, Dmitry Vyukov wrote: > You can also find some reasons in the Why section of LLVM-Linux project: > http://llvm.linuxfoundation.org/index.php/Main_Page >From that: - LLVM/Clang is a fast moving project with many things fixed quickly and features added.

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Peter Zijlstra
On Fri, Mar 17, 2017 at 08:26:42PM +0100, Peter Zijlstra wrote: > On Fri, Mar 17, 2017 at 08:05:16PM +0100, Dmitry Vyukov wrote: > > You can also find some reasons in the Why section of LLVM-Linux project: > > http://llvm.linuxfoundation.org/index.php/Main_Page > > From that: > > - LLVM/Clang

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Peter Zijlstra
On Fri, Mar 17, 2017 at 11:52:01AM -0700, Michael Davidson wrote: > On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra wrote: > > > > Be that as it may; what you construct above is disgusting. Surely the > > code can be refactored to not look like dog vomit? > > > > Also; its

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Borislav Petkov
On Fri, Mar 17, 2017 at 07:47:33PM +0100, Dmitry Vyukov wrote: > This problem is more general and is not specific to clang. It equally > applies to different versions of gcc, different arches and different > configs (namely, anything else than what a developer used for > testing). I guess. We do

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Dmitry Vyukov
On Fri, Mar 17, 2017 at 7:57 PM, Borislav Petkov wrote: > On Fri, Mar 17, 2017 at 07:47:33PM +0100, Dmitry Vyukov wrote: >> This problem is more general and is not specific to clang. It equally >> applies to different versions of gcc, different arches and different >> configs

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Michael Davidson
On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra wrote: > > Be that as it may; what you construct above is disgusting. Surely the > code can be refactored to not look like dog vomit? > > Also; its not immediately obvious conf->copies is 'small' and this > doesn't blow up the

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Dmitry Vyukov
On Fri, Mar 17, 2017 at 7:03 PM, Borislav Petkov wrote: > On Fri, Mar 17, 2017 at 01:32:00PM +0100, Alexander Potapenko wrote: >> > IIUC there's only a handful of VLAIS instances in LLVM code, why not >> Sorry, "kernel code", not "LLVM code". >> > just drop them for the sake of

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Alexander Potapenko
On Fri, Mar 17, 2017 at 1:31 PM, Alexander Potapenko wrote: > On Fri, Mar 17, 2017 at 1:08 PM, Peter Zijlstra wrote: >> On Thu, Mar 16, 2017 at 05:15:19PM -0700, Michael Davidson wrote: >>> Replace a variable length array in a struct by allocating >>> the

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Peter Zijlstra
On Fri, Mar 17, 2017 at 01:31:23PM +0100, Alexander Potapenko wrote: > On Fri, Mar 17, 2017 at 1:08 PM, Peter Zijlstra wrote: > > On Thu, Mar 16, 2017 at 05:15:19PM -0700, Michael Davidson wrote: > >> Replace a variable length array in a struct by allocating > >> the memory

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Alexander Potapenko
On Fri, Mar 17, 2017 at 1:08 PM, Peter Zijlstra wrote: > On Thu, Mar 16, 2017 at 05:15:19PM -0700, Michael Davidson wrote: >> Replace a variable length array in a struct by allocating >> the memory for the entire struct in a char array on the stack. >> >> Signed-off-by:

Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-17 Thread Peter Zijlstra
On Thu, Mar 16, 2017 at 05:15:19PM -0700, Michael Davidson wrote: > Replace a variable length array in a struct by allocating > the memory for the entire struct in a char array on the stack. > > Signed-off-by: Michael Davidson > --- > drivers/md/raid10.c | 9 - > 1 file

[PATCH 6/7] md/raid10, LLVM: get rid of variable length array

2017-03-16 Thread Michael Davidson
Replace a variable length array in a struct by allocating the memory for the entire struct in a char array on the stack. Signed-off-by: Michael Davidson --- drivers/md/raid10.c | 9 - 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/md/raid10.c