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Commit 7ed5cb2b authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

Remove nid_lock from alloc_fresh_huge_page 



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: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e3aded3c

mm/hugetlb.c

+7 −3
Original line number Original line Diff line number Diff line
@@ -104,15 +104,19 @@ static int alloc_fresh_huge_page(void) 
{

{

	static int prev_nid;

	static int prev_nid;

	struct page *page;

	struct page *page;

	static DEFINE_SPINLOCK(nid_lock);

	int nid;

	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);

	nid = next_node(prev_nid, node_online_map);

	if (nid == MAX_NUMNODES)

	if (nid == MAX_NUMNODES)

		nid = first_node(node_online_map);

		nid = first_node(node_online_map);

	prev_nid = nid;

	prev_nid = nid;

	spin_unlock(&nid_lock);





	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,

	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,

					HUGETLB_PAGE_ORDER);

					HUGETLB_PAGE_ORDER);