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authorDavid Rientjes <rientjes@google.com>2017-02-24 14:58:47 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:55 -0800
commitdef5efe0376501ef7bd6b53ed061512c142e59aa (patch)
tree46c957c37989924f2a970f09e15fc90d757999bf /mm
parent712c604dcdf8186295e2af694adf52c6842ad100 (diff)
downloadlinux-def5efe0376501ef7bd6b53ed061512c142e59aa.tar.gz
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/madvise.c51
-rw-r--r--mm/mmap.c8
2 files changed, 46 insertions, 13 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index 0012071a6..11fc65f 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -92,14 +92,28 @@ static long madvise_behavior(struct vm_area_struct *vma,
case MADV_MERGEABLE:
case MADV_UNMERGEABLE:
error = ksm_madvise(vma, start, end, behavior, &new_flags);
- if (error)
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
goto out;
+ }
break;
case MADV_HUGEPAGE:
case MADV_NOHUGEPAGE:
error = hugepage_madvise(vma, &new_flags, behavior);
- if (error)
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
goto out;
+ }
break;
}
@@ -120,15 +134,37 @@ static long madvise_behavior(struct vm_area_struct *vma,
*prev = vma;
if (start != vma->vm_start) {
- error = split_vma(mm, vma, start, 1);
- if (error)
+ if (unlikely(mm->map_count >= sysctl_max_map_count)) {
+ error = -ENOMEM;
goto out;
+ }
+ error = __split_vma(mm, vma, start, 1);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
+ goto out;
+ }
}
if (end != vma->vm_end) {
- error = split_vma(mm, vma, end, 0);
- if (error)
+ if (unlikely(mm->map_count >= sysctl_max_map_count)) {
+ error = -ENOMEM;
+ goto out;
+ }
+ error = __split_vma(mm, vma, end, 0);
+ if (error) {
+ /*
+ * madvise() returns EAGAIN if kernel resources, such as
+ * slab, are temporarily unavailable.
+ */
+ if (error == -ENOMEM)
+ error = -EAGAIN;
goto out;
+ }
}
success:
@@ -136,10 +172,7 @@ success:
* vm_flags is protected by the mmap_sem held in write mode.
*/
vma->vm_flags = new_flags;
-
out:
- if (error == -ENOMEM)
- error = -EAGAIN;
return error;
}
diff --git a/mm/mmap.c b/mm/mmap.c
index 1cec28d..499b988 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2499,11 +2499,11 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
}
/*
- * __split_vma() bypasses sysctl_max_map_count checking. We use this on the
- * munmap path where it doesn't make sense to fail.
+ * __split_vma() bypasses sysctl_max_map_count checking. We use this where it
+ * has already been checked or doesn't make sense to fail.
*/
-static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long addr, int new_below)
+int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr, int new_below)
{
struct vm_area_struct *new;
int err;