From def5efe0376501ef7bd6b53ed061512c142e59aa Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Fri, 24 Feb 2017 14:58:47 -0800 Subject: 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 Cc: Jonathan Corbet Cc: Johannes Weiner Cc: Jerome Marchand Cc: "Kirill A. Shutemov" Cc: Michael Kerrisk Cc: Anshuman Khandual Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/mm.h b/include/linux/mm.h index c6fcba1d1ae5..ed233b002e33 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2041,8 +2041,10 @@ extern struct vm_area_struct *vma_merge(struct mm_struct *, unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t, struct mempolicy *, struct vm_userfaultfd_ctx); extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *); -extern int split_vma(struct mm_struct *, - struct vm_area_struct *, unsigned long addr, int new_below); +extern int __split_vma(struct mm_struct *, struct vm_area_struct *, + unsigned long addr, int new_below); +extern int split_vma(struct mm_struct *, struct vm_area_struct *, + unsigned long addr, int new_below); extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *); extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *, struct rb_node **, struct rb_node *); -- cgit v1.2.3