linux-kernel - Re: [PATCH] selftests/vm: Fix map_hugetlb length used for testing read and write

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Date:   Mon, 17 Feb 2020 11:10:54 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Michael Ellerman <mpe@...erman.id.au>,
        Shuah Khan <shuah@...nel.org>
Cc:     linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] selftests/vm: Fix map_hugetlb length used for testing
 read and write

On Sat, 2020-02-15 at 03:49 -0300, Leonardo Bras wrote:
> Hello Christophe, thank you for the patch.
> 
> On Thu, 2020-02-06 at 08:42 +0000, Christophe Leroy wrote:
> > Commit fa7b9a805c79 ("tools/selftest/vm: allow choosing mem size and
> > page size in map_hugetlb") added the possibility to change the size
> > of memory mapped for the test, but left the read and write test using
> > the default value. This is unnoticed when mapping a length greater
> > than the default one, but segfaults otherwise.
> > 
> > Fix read_bytes() and write_bytes() by giving them the real length.
> > 
> > Also fix the call to munmap().
> > 
> > Fixes: fa7b9a805c79 ("tools/selftest/vm: allow choosing mem size and page size in map_hugetlb")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> > ---
> >  tools/testing/selftests/vm/map_hugetlb.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/vm/map_hugetlb.c b/tools/testing/selftests/vm/map_hugetlb.c
> > index 5a2d7b8efc40..6af951900aa3 100644
> > --- a/tools/testing/selftests/vm/map_hugetlb.c
> > +++ b/tools/testing/selftests/vm/map_hugetlb.c
> > @@ -45,20 +45,20 @@ static void check_bytes(char *addr)
> >  	printf("First hex is %x\n", *((unsigned int *)addr));
> >  }
> >  
> > -static void write_bytes(char *addr)
> > +static void write_bytes(char *addr, size_t length)
> >  {
> >  	unsigned long i;
> >  
> > -	for (i = 0; i < LENGTH; i++)
> > +	for (i = 0; i < length; i++)
> >  		*(addr + i) = (char)i;
> >  }
> >  
> > -static int read_bytes(char *addr)
> > +static int read_bytes(char *addr, size_t length)
> >  {
> >  	unsigned long i;
> >  
> >  	check_bytes(addr);
> > -	for (i = 0; i < LENGTH; i++)
> > +	for (i = 0; i < length; i++)
> >  		if (*(addr + i) != (char)i) {
> >  			printf("Mismatch at %lu\n", i);
> >  			return 1;
> > @@ -96,11 +96,11 @@ int main(int argc, char **argv)
> >  
> >  	printf("Returned address is %p\n", addr);
> >  	check_bytes(addr);
> > -	write_bytes(addr);
> > -	ret = read_bytes(addr);
> > +	write_bytes(addr, length);
> > +	ret = read_bytes(addr, length);
> >  
> >  	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
> > -	if (munmap(addr, LENGTH)) {
> > +	if (munmap(addr, length)) {
> >  		perror("munmap");
> >  		exit(1);
> >  	}
> 
> I agree with you, it's a needed fix.
> 
> FWIW:
> Reviwed-by: Leonardo Bras <leonardo@...ux.ibm.com>
Sorry, typo.
Reviewed-by: Leonardo Bras <leonardo@...ux.ibm.com>

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