bug#19607: issue with Emacs 24.4.1 but not with 24.3.1 : changed on disk; really edit the buffer

[Paul Eggert <eggert@cs.ucla.edu>]

[-- Attachment #1: Type: text/plain, Size: 822 bytes --]

Thanks, the key problem is the fourth time the breakpoint is hit, where 
the output in your log looks like this:

Breakpoint 3, Fverify_visited_file_modtime (buf=27021317) at fileio.c:5338
5338      if (timespec_cmp (mtime, b->modtime) == 0
(gdb) p mtime
$7 = {
   tv_sec = 1422018451,
   tv_nsec = 132061000
}
(gdb) p b->modtime
$8 = {
   tv_sec = 1422018451,
   tv_nsec = 40059000
}

The two time stamps should be the same, but the nanoseconds component 
differ (the tv_sec components are the same, which is why we don't 
observe any bugs in the strace output).

I suspect a bug in the file system.  Can you please try running the 
attached program, with the current directory being that file system?  It 
should take about 2 seconds.  You might try running it twice (it may 
depend on whether the file already exists).

[-- Attachment #2: test.c --]
[-- Type: text/plain, Size: 1004 bytes --]

#include <unistd.h>
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>

int
main (void)
{
  char const *filename = "test.txt";
  int fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666);
  if (fd < 0)
    return perror ("open"), 1;
  static char const message[] = "This is a test.\n";
  int messagelen = sizeof message - 1;
  if (write (fd, message, messagelen) != messagelen)
    return perror ("write"), 1;
  if (fsync (fd) != 0)
    return perror ("fsync"), 1;
  struct stat st1, st2;
  if (fstat (fd, &st1) != 0)
    return perror ("fstat"), 1;
  if (close (fd) != 0)
    return perror ("close"), 1;
  sleep (2);
  if (stat (filename, &st2) != 0)
    return perror ("stat"), 1;
  if (! (st1.st_mtim.tv_sec == st2.st_mtim.tv_sec
	 && st1.st_mtim.tv_nsec == st2.st_mtim.tv_nsec))
    {
      printf ("last-modified times do not conform to:\n"
	      "http://pubs.opengroup.org/onlinepubs/"
	      "9699919799/basedefs/V1_chap04.html#tag_04_08\n");
      return 1;
    }
  return 0;
}