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Date:      Mon, 20 Mar 1995 17:30:01 -0800
From:      ache@astral.msk.su
To:        freebsd-bugs
Subject:   kern/260: msync(...,0) broken & msync don't update mod times
Message-ID:  <199503210130.RAA20019@freefall.cdrom.com>
In-Reply-To: Your message of Tue, 21 Mar 1995 04:27:14 %2B0300 <199503210127.EAA13069@deep-thought.demos.su>
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>Number:         260
>Category:       kern
>Synopsis:       msync can't handle 0 and don't bother to update mod times
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs (FreeBSD bugs mailing list)
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Mar 20 17:30:01 1995
>Originator:     Andrey A. Chernov;  Black Mage
>Organization:
Ha-olahm Yetzirah
>Release:        FreeBSD 2.1.0-Development i386
>Environment:

	-current

>Description:

1) msync(..., 0) always return -1
2) msync() don't update file times, as manpage sayd:
       The  msync system  call writes any modified pages back to
       the filesystem and updates the file modification time.
			  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>How-To-Repeat:

---------------------------------- cut here ----------------------------
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <stdio.h>

static char             ICDactpath[] = "testfile";
static char             *ICDactpointer;
static int              ICDactfd;
static int              ICDactsize;

#if	defined(MAP_FILE)
#define MAP__ARG	(MAP_FILE | MAP_SHARED)
#else
#define MAP__ARG	(MAP_SHARED)
#endif	/* defined(MAP_FILE) */

char *
ICDread()
{
    struct stat		Sb;
    int i;

    if ((ICDactfd = open(ICDactpath, O_WRONLY|O_TRUNC|O_CREAT, 0666)) < 0) {
	perror("open");
	fprintf(stderr, "read: cant open %s\n", ICDactpath);
	exit(1);
    }
    for (i = 0; i < 7; i++)
	write(ICDactfd, "1234567890", 10);
    if (close(ICDactfd) < 0) {
	perror("close");
	fprintf(stderr, "Close: cant close %s\n", ICDactpath);
	exit(1);
    }

    if ((ICDactfd = open(ICDactpath, O_RDWR)) < 0) {
	perror("open");
	fprintf(stderr, "read: cant open %s\n", ICDactpath);
	exit(1);
    }

    if (fstat(ICDactfd, &Sb) < 0) {
	perror("fstat");
	fprintf(stderr, "read: cant fstat %d %s\n", ICDactfd, ICDactpath);
	exit(1);
    }
    ICDactsize = Sb.st_size;
    ICDactpointer = mmap((caddr_t)0, ICDactsize, PROT_READ|PROT_WRITE,
			MAP__ARG, ICDactfd, (off_t)0);
    if (ICDactpointer == (char *)-1) {
	perror("mmap");
	fprintf(stderr, "read: cant mmap %d %s\n", ICDactfd, ICDactpath);
	exit(1);
    }

    return ICDactpointer;
}

ICDclose()
{
    if (ICDactpointer) {
	if (msync(ICDactpointer, ICDactsize) < 0) {
	    perror("msync");
	    fprintf(stderr, "Close: cant msync %s in closeactive()\n",  ICDactpath);
	}

	if (munmap(ICDactpointer, ICDactsize) < 0) {
	    perror("munmap");
	    fprintf(stderr, "Close: cant munmap\n", ICDactpath);
	}
	ICDactpointer = NULL;
	if (close(ICDactfd) < 0) {
	   perror("close");
	   fprintf(stderr, "Close: cant close %s\n", ICDactpath);
	   exit(1);
	}
    }
}

ICDwrite()
{
    /* No-op. */
		    /* ICDactsize */
    if (msync(ICDactpointer, 0) < 0) {
	perror("msync");
	fprintf(stderr, "Write: cant msync %s\n", ICDactpath);
    }
}

spy() {
	system("cat testfile; echo; ls -l testfile");
}

main()
{
	char *file_p;
	int to_sleep = 2;

	file_p = ICDread();

	fprintf(stderr, "Original file and time\n");
	spy();
	*(file_p + 20) = '\n';
#if 0
	fprintf(stderr, "After 1st write to mapped region\n");
	spy();
#endif
	sleep(to_sleep);
	*(file_p + 30) = '\n';
#if 0
	fprintf(stderr, "After 2nd write to mapped region and sleep()\n");
	spy();
#endif
	ICDwrite();
	fprintf(stderr, "After msync(..., 0)\n");
	spy();
	sleep(to_sleep);
	ICDclose();
	fprintf(stderr, "After sleep(), msync(..., size) and close()\n");
	spy();
	unlink(ICDactpath);
}
---------------------------------- cut here ----------------------------

Here FreeBSD-current results:

Original file and time
1234567890123456789012345678901234567890123456789012345678901234567890
-rw-r--r--  1 ache  wheel  70 Mar  4 20:50 testfile
msync: Invalid argument
Write: cant msync testfile
After msync(..., 0)
12345678901234567890
234567890
234567890123456789012345678901234567890
-rw-r--r--  1 ache  wheel  70 Mar  4 20:50 testfile
After sleep(), msync(..., size) and close()
12345678901234567890
234567890
234567890123456789012345678901234567890
-rw-r--r--  1 ache  wheel  70 Mar  4 20:50 testfile

As you can see, msync(..., 0) works, but returns -1 and EINVAL
in -current. File modification times not updated at all.

>Fix:
	
	Unknown

>Audit-Trail:
>Unformatted:
help

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