The patch titled
Remove nid_lock from alloc_fresh_huge_page
has been added to the -mm tree. Its filename is
remove-nid_lock-from-alloc_fresh_huge_page.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Remove nid_lock from alloc_fresh_huge_page
From: Hugh Dickins <hugh@xxxxxxxxxxx>
The fix to that race in alloc_fresh_huge_page() which could give an illegal
node ID did not need nid_lock at all: the fix was to replace static int nid
by static int prev_nid and do the work on local int nid. nid_lock did make
sure that racers strictly roundrobin the nodes, but that's not something we
need to enforce strictly. Kill nid_lock.
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff -puN mm/hugetlb.c~remove-nid_lock-from-alloc_fresh_huge_page mm/hugetlb.c
--- a/mm/hugetlb.c~remove-nid_lock-from-alloc_fresh_huge_page
+++ a/mm/hugetlb.c
@@ -107,15 +107,19 @@ static int alloc_fresh_huge_page(void)
{
static int prev_nid;
struct page *page;
- static DEFINE_SPINLOCK(nid_lock);
int nid;
- spin_lock(&nid_lock);
+ /*
+ * Copy static prev_nid to local nid, work on that, then copy it
+ * back to prev_nid afterwards: otherwise there's a window in which
+ * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
+ * But we don't need to use a spin_lock here: it really doesn't
+ * matter if occasionally a racer chooses the same nid as we do.
+ */
nid = next_node(prev_nid, node_online_map);
if (nid == MAX_NUMNODES)
nid = first_node(node_online_map);
prev_nid = nid;
- spin_unlock(&nid_lock);
page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
HUGETLB_PAGE_ORDER);
_
Patches currently in -mm which might be from hugh@xxxxxxxxxxx are
origin.patch
pa-risc-use-page-allocator-instead-of-slab-allocator.patch
x86_64-acpi-disable-srat-when-numa-emulation-succeeds.patch
remove-nid_lock-from-alloc_fresh_huge_page.patch
ext2-reservations.patch
fix-for-ext2-reservation.patch
ext2-balloc-use-io_error-label.patch
mm-variable-length-argument-support.patch
add-__gfp_movable-for-callers-to-flag-allocations-from-high-memory-that-may-be-migrated-swap-prefetch.patch
coredump-masking-bound-suid_dumpable-sysctl.patch
coredump-masking-reimplementation-of-dumpable-using-two-flags.patch
coredump-masking-add-an-interface-for-core-dump-filter.patch
coredump-masking-elf-enable-core-dump-filtering.patch
coredump-masking-elf-fdpic-remove-an-unused-argument.patch
coredump-masking-elf-fdpic-enable-core-dump-filtering.patch
coredump-masking-documentation-for-proc-pid-coredump_filter.patch
prio_tree-debugging-patch.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
