Messages in this thread | | | Subject | Re: /proc/$pid/pagemap troubles | From | Dave Hansen <> | Date | Tue, 31 Jul 2007 16:06:21 -0700 |
| |
On Wed, 2007-08-01 at 00:58 +0200, Andreas Schwab wrote: > Matt Mackall <mpm@selenic.com> writes: > > > On Tue, Jul 31, 2007 at 01:36:14PM -0700, Dave Hansen wrote: > >> Since the pagemap code has a little header on it to help describe the > >> format, I wrote a little c program to parse its output. I get some > >> strange results. If I do this: > >> > >> fd = open("/proc/1/pagemap", O_RDONLY); > >> count = read(fd, &endianness, 1); > >> > >> count will always be 4. > > > > Known bug, fixed in my pending and not-currently-working update. It > > ought to return 0 for short reads. > > That's not a good choice. Returning 0 means EOF, but there is actually > data to be read.
This should actually be pretty easy to fix. We have a nice PAGE_SIZE buffer. So, if we are unaligned and would have overflowed the PAGE_SIZE buffer, we return a short read.
If they ask for a <sizeof(unsigned long) read, we can copy that into the PAGE_SIZE buffer, then just copy_to_user() the portion that was asked for.
-- Dave
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |