Date: Wed, 10 Nov 2004 14:09:33 +0100 From: =?iso-8859-2?q?S=B3awek_=AFak?= <zaks@prioris.mini.pw.edu.pl> To: current@freebsd.org Subject: MMAP(2) troubles on smbfs Message-ID: <86lld9df5e.fsf@thirst.unx.era.pl>
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Hi,
I've noticed that msyncing the mmap pointer or fsyncing the file descriptor
is required when filesystem where mmap'ed file resides is smbfs. I use
MMAP_SHARED mode for mmap.
I attach a small test program. I've tried both 5.3-STABLE and 5.2-CURRENT
(built on March 2.) on the client and Samba, Windows XP on the server.
The same operation seems to work fine on both local filesystem and NFS
(ie. no syncing is necessary). Unmounting the filesystem doesn't help - the
changes are not flushed to the file.
/S
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Content-Disposition: inline; filename=mmap.c
#include <sys/mman.h>
#include <stdio.h>
#include <fcntl.h>
int main()
{
int fd;
void *ptr;
fd = open("/mnt/tmp/file", O_RDWR);
if (fd < 0) {
perror("open");
exit(1);
}
ptr = mmap(NULL, 10, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (ptr == MAP_FAILED) {
perror("mmap");
exit(1);
}
*(char *)ptr = '/';
#if 0
if (msync(ptr, 10, MS_SYNC) < 0) {
perror("msync");
exit(1);
}
if (fsync(fd) < 0) {
perror("fsync");
exit(1);
}
#endif
if (munmap(ptr, 10) < 0) {
perror("munmap");
exit(1);
}
if (close(fd) < 0) {
perror("close");
exit(1);
}
return 0;
}
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