I have a new feature for the Linux virtual filesystem. My patch against
2.1.118 adds a new fcntl() function (F_SET_SIGVFS) that instructs the VFS
to send a signal to userland if a specific inode (file/dir) has changed. =
You only
have to open the file/dir for reading and give a mask and signalnr to fcn=
tl().
Thats all. The program wakes up when something happens and you can do a=20
fstat() or readdir() to figure out _what_ the changes are. Simple, small,=
no obscure API.
Currently the only way to do this is by frequently polling which is mostl=
y not
what you would like to do.
Please check the patch out. I dont see any complications.
Cheers,
Rene Janssen
cc me :
<reney@plex.nl>
/* small test program for F_SET_SIGVFS
*/
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
static int stop;
void sigusr1(int sig)
{
=09printf("VFS signal\n");=09
}
void stopit(int sig)
{
=09stop =3D 1;
}
int main(int argc, char *argv[])
{
=09int err,fh =3D -1;
=09struct sigvfsinfo info;
=09struct sigaction sa;
=09fh =3D open(argv[1],O_RDONLY);
=09if (!fh) {=20
=09=09perror("open");
=09=09exit(1);
=09}
=09
=09sigemptyset(&sa.sa_mask);
=09sa.sa_handler =3D &sigusr1;
=09sa.sa_flags =3D 0;
=09sigaction(SIGUSR1,&sa,NULL);
=09sigemptyset(&sa.sa_mask);
=09sa.sa_handler =3D &stopit;
=09sa.sa_flags =3D 0;
=09sigaction(SIGINT,&sa,NULL);
=09
=09info.sig =3D SIGUSR1;
=09
//=09info.mask =3D F_ATTR_MTIME | F_ATTR_ATIME | F_ATTR_CTIME;
//=09info.mask =3D F_ATTR_UID | F_ATTR_GID;
//=09info.mask =3D F_ATTR_MODE;
=09info.mask =3D F_MKDIR | F_RMDIR | F_CREATE | F_RENAME;
//=09info.mask =3D F_ATTR_ATIME;
//=09info.mask =3D F_UNLINK;
=09
=09err =3D fcntl(fh,F_SET_SIGVFS,&info);
=09if (err) {
=09=09perror("fcntl");
=09=09exit(1);
=09}=09
=09do sleep(~0);
=09while (!stop);
=09printf("exiting\n");
//=09err =3D fcntl(fh,F_CLR_SIGVFS,NULL);
//=09close(fh);=09
=09exit(0);
}
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