mm: add a field to store names for private anonymous memory

Userspace processes often have multiple allocators that each do
anonymous mmaps to get memory.  When examining memory usage of
individual processes or systems as a whole, it is useful to be
able to break down the various heaps that were allocated by
each layer and examine their size, RSS, and physical memory
usage.

This patch adds a user pointer to the shared union in
vm_area_struct that points to a null terminated string inside
the user process containing a name for the vma.  vmas that
point to the same address will be merged, but vmas that
point to equivalent strings at different addresses will
not be merged.

Userspace can set the name for a region of memory by calling
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name);
Setting the name to NULL clears it.

The names of named anonymous vmas are shown in /proc/pid/maps
as [anon:<name>] and in /proc/pid/smaps in a new "Name" field
that is only present for named vmas.  If the userspace pointer
is no longer valid all or part of the name will be replaced
with "<fault>".

The idea to store a userspace pointer to reduce the complexity
within mm (at the expense of the complexity of reading
/proc/pid/mem) came from Dave Hansen.  This results in no
runtime overhead in the mm subsystem other than comparing
the anon_name pointers when considering vma merging.  The pointer
is stored in a union with fieds that are only used on file-backed
mappings, so it does not increase memory usage.

Change-Id: Ie2ffc0967d4ffe7ee4c70781313c7b00cf7e3092
Signed-off-by: Colin Cross <ccross@android.com>
net: wireless: bcmdhd: Remove chatty message from wl_cfgp2p_act_frm_search

Change-Id: I06ffddddf239443f3684f97a5c31b6872c89d769
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
net: ipv6: add missing lock in ping_v6_sendmsg

Bug: 9469865
Change-Id: I5e9db559d22e35d27fa1df948b70c70ed8b42115
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: ipv6: fix wrong ping_v6_sendmsg return value

ping_v6_sendmsg currently returns 0 on success. It should return
the number of bytes written instead.

Bug: 9469865
Change-Id: I14aad6018f0c3fd92dad315bc3ade04c0b3982e0
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>