proc: fix vma display mismatch between /proc/pid/{maps,smaps}

proc: fix vma display mismatch between /proc/pid/{maps,smaps}

[ backport of 7c88db0cb589df980acfb2f73c3595a0653004ec to 2.7.27.3 by Joe
Korty <joe.korty@ccur.com ]

proc: fix vma display mismatch between /proc/pid/{maps,smaps}

Commit 4752c369789250eafcd7813e11c8fb689235b0d2 aka
"maps4: simplify interdependence of maps and smaps" broke /proc/pid/smaps,
causing it to display some vmas twice and other vmas not at all.  For example:

    grep .- /proc/1/smaps >/tmp/smaps; diff /proc/1/maps /tmp/smaps

    1  25d24
    2  < 7fd7e23aa000-7fd7e23ac000 rw-p 7fd7e23aa000 00:00 0
    3  28a28
    4  > ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0  [vsyscall]

The bug has something to do with setting m->version before all the
seq_printf's have been performed.  show_map was doing this correctly,
but show_smap was doing this in the middle of its seq_printf sequence.
This patch arranges things so that the setting of m->version in show_smap
is also done at the end of its seq_printf sequence.

Testing: in addition to the above grep test, for each process I summed
up the 'Rss' fields of /proc/pid/smaps and compared that to the 'VmRSS'
field of /proc/pid/status.  All matched except for Xorg (which has a
/dev/mem mapping which Rss accounts for but VmRSS does not).  This result
gives us some confidence that neither /proc/pid/maps nor /proc/pid/smaps
are any longer skipping or double-counting vmas.

Signed-off-by: Joe Korty <joe.korty@ccur.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>