On Wed, Jul 07, 2010 at 10:03:39PM +0530, Aneesh Kumar K. V wrote: > On Wed, 7 Jul 2010 10:45:11 -0400, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > > On Wed, Jul 07, 2010 at 03:35:50PM +0200, Miklos Szeredi wrote: > > > On Wed, 7 Jul 2010, J. Bruce Fields wrote: > > > > > > If you use sys or proc, is it possible to get the uuid from a file > > > > > > descriptor or pathname without races? > > > > > > > > > > You can do stat/fstat to find out the device number (which is unique, > > > > > but not persistent) > > > > > > > > Is it really unique over time? (Can't a given st_dev value map to one > > > > filesystem now, and another later?) > > > > > > It's unique at a single point in time. But if you have a reference > > > (e.g. open file descriptor) on the mount then that's not a problem. > > > > > > fd = open(path, ...); > > > fstat(fd, &st); > > > search st.st_dev in mountinfo > > > close(fd) > > > > > > is effectively the same as an getuuid(path) syscall (lazy unmounted > > > filesystems will not be found in mountinfo, but the reference is still > > > there so st_dev will not be reused for other filesystems). > > > > OK, cool. > > > > That still leaves the problem that there isn't always an underlying > > block device, and/or when there is it doesn't always uniquely specify > > the filesystem. > > > > And for this reason we would need this as a syscall right ? That's the only solution I see. (Or use an xattr?) --b. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
