Messages in this thread | | | Date | Mon, 14 Sep 2015 11:53:46 +0100 | From | Will Deacon <> | Subject | LTP regressions due to 6dc296e7df4c ("mm: make sure all file VMAs have ->vm_ops set") |
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Hi Kirill,
Your patch 6dc296e7df4c ("mm: make sure all file VMAs have ->vm_ops set") causes some mmap regressions in LTP, which appears to use a MAP_PRIVATE mmap of /dev/zero as a way to get anonymous pages in some of its tests (specifically mmap10 [1]).
Dead simple reproducer below. Is this change in behaviour intentional?
Will
[1] http://sourceforge.net/p/ltp/git/ci/1eb440c2b5fe43a3e5023015a16aa5d7d3385b1e/tree/testcases/kernel/syscalls/mmap/mmap10.c
--->8
#include <sys/mman.h> #include <sys/stat.h>
#include <fcntl.h> #include <stdio.h>
#define MAP_SZ 5*1024*1024
int main(void) { char *foo; int fd;
fd = open("/dev/zero", O_RDWR, 0666); if (fd < 0) { perror(NULL); return fd; }
foo = mmap(NULL, MAP_SZ, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); if (foo == MAP_FAILED) { perror(NULL); return -1; }
foo[MAP_SZ >> 1] = 0; // Generates SIGBUS with 4.3-rc1 return 0; }
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