mm, madvise: fail with ENOMEM when splitting vma will hit max_map_count
authorDavid Rientjes <rientjes@google.com>
Fri, 24 Feb 2017 22:58:47 +0000 (14:58 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 25 Feb 2017 01:46:55 +0000 (17:46 -0800)
commitdef5efe0376501ef7bd6b53ed061512c142e59aa
tree46c957c37989924f2a970f09e15fc90d757999bf
parent712c604dcdf8186295e2af694adf52c6842ad100
mm, madvise: fail with ENOMEM when splitting vma will hit max_map_count

If madvise(2) advice will result in the underlying vma being split and
the number of areas mapped by the process will exceed
/proc/sys/vm/max_map_count as a result, return ENOMEM instead of EAGAIN.

EAGAIN is returned by madvise(2) when a kernel resource, such as slab,
is temporarily unavailable.  It indicates that userspace should retry
the advice in the near future.  This is important for advice such as
MADV_DONTNEED which is often used by malloc implementations to free
memory back to the system: we really do want to free memory back when
madvise(2) returns EAGAIN because slab allocations (for vmas, anon_vmas,
or mempolicies) cannot be allocated.

Encountering /proc/sys/vm/max_map_count is not a temporary failure,
however, so return ENOMEM to indicate this is a more serious issue.  A
followup patch to the man page will specify this behavior.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701241431120.42507@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Documentation/sysctl/vm.txt
Documentation/vm/ksm.txt
include/linux/mm.h
mm/madvise.c
mm/mmap.c