On Tue, 9 Jun 2015 18:39:02 -0700 Calvin Owens <calvinow...@fb.com> wrote:
> On Tuesday 06/09 at 14:13 -0700, Andrew Morton wrote: > > On Mon, 8 Jun 2015 20:39:33 -0700 Calvin Owens <calvinow...@fb.com> wrote: > > > > > Currently, /proc/<pid>/map_files/ is restricted to CAP_SYS_ADMIN, and > > > is only exposed if CONFIG_CHECKPOINT_RESTORE is set. > > > > > > This interface very useful because it allows userspace to stat() > > > deleted files that are still mapped by some process, which enables a > > > much quicker and more accurate answer to the question "How much disk > > > space is being consumed by files that are deleted but still mapped?" > > > than is currently possible. > > > > Why is that information useful? > > > > I could perhaps think of some use for "How much disk space is being > > consumed by files that are deleted but still open", but to count the > > mmapped-then-unlinked files while excluding the opened-then-unlinked > > files seems damned peculiar. > > Let's phrase the question a bit more generically: > > "How much disk space is being consumed by files that have been > unlinked, but are still referenced by some process?" > > There are two pieces to this problem: > 1) Unlinked files that are still open (whether mapped or not) > 2) Unlinked files that are not open, but are still mapped > > You can track down everything in (1) using /proc/<pid>/fd/*, and you > can use stat() to figure out how much space they're using. This doesn't work if the mapped file has been unlinked? What does the /proc/pid/map_files listing look like for these? > Does that all seem sensible? Spose so. Please capture all this info in the changelog. It all seems a bit awkward though. If we want to know "how much disk space is this process using" (or similar) then I wonder what a syscall (or prctl mode?) which does this would look like. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
