Re: [PATCH 0/10] Fix page_mkwrite() for blocksize < pagesize (version 3)

Jan Kara
2009-06-16T14:42:27Z

[-- Attachment #1: Type: text/plain, Size: 739 bytes --]

On Tue 16-06-09 10:34:24, Christoph Hellwig wrote:
> On Mon, Jun 15, 2009 at 07:59:47PM +0200, Jan Kara wrote:
> >
> > patches below are an attempt to solve problems filesystems have with
> > page_mkwrite() when blocksize < pagesize (see the changelog of the second patch
> > for details).
>
> It would be useful if you had a test case reproducing these issues,
> so that I can verify how well your patches work in various scenarios.
Good point, I should have mentioned in the changelog: fsx-linux is able
to trigger the problem quite quickly.
I have also written a simple program for initial testing of the fix
(works only for 1K blocksize and 4K pagesize) - it's attached.

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR

[-- Attachment #2: test-mkwrite.c --]
[-- Type: text/x-c++src, Size: 1242 bytes --]

#define _XOPEN_SOURCE 500
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>

#define MMAP_THREADS 4

void map_file(int fd)
{
char *addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
int i;

if (addr == MAP_FAILED) {
perror("mmap");
exit(1);
}
while (1) {
for (i = 0; i < 128; i++)
addr[i + 1024] = 'c';
}
}

char buf2[4096] __attribute__ ((aligned (4096)));

int main(int argc, char **argv)
{
int i;
int ret;
int fd;
char buf[1024];

if (argc != 2) {
printf("Usage: test-mkwrite <file>\n");
return 1;
}
fd = open(argv[1], O_RDWR | O_CREAT | O_TRUNC, 0644);
if (fd < 0) {
perror("open");
return 1;
}
memset(buf, 'a', sizeof(buf));
pwrite(fd, buf, sizeof(buf), 0);

for (i = 0; i < MMAP_THREADS; i++) {
ret = fork();
if (ret < 0) {
perror("fork");
return 1;
} else if (ret == 0)
map_file(fd);
}
close(fd);

memset(buf2, 'b', sizeof(buf2));
fd = open(argv[1], O_RDWR | O_DIRECT);
if (fd < 0) {
perror("dopen");
return 1;
}
while (1) {
if (pwrite(fd, buf2, 4096, 4096) < 0)
perror("pwrite");
usleep(10000000);
ftruncate(fd, 1024);
usleep(10000000);
}

return 0;
}