The patch titled
thp: split_huge_page anon_vma ordering dependency
has been removed from the -mm tree. Its filename was
thp-split_huge_page-anon_vma-ordering-dependency.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: thp: split_huge_page anon_vma ordering dependency
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
This documents how split_huge_page is safe vs new vma inserctions into the
anon_vma that may have already released the anon_vma->lock but not
established pmds yet when split_huge_page starts.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 16 ++++++++++++++++
mm/rmap.c | 4 ++++
2 files changed, 20 insertions(+)
diff -puN mm/huge_memory.c~thp-split_huge_page-anon_vma-ordering-dependency mm/huge_memory.c
--- a/mm/huge_memory.c~thp-split_huge_page-anon_vma-ordering-dependency
+++ a/mm/huge_memory.c
@@ -841,6 +841,19 @@ static void __split_huge_page(struct pag
continue;
mapcount += __split_huge_page_splitting(page, vma, addr);
}
+ /*
+ * It is critical that new vmas are added to the tail of the
+ * anon_vma list. This guarantes that if copy_huge_pmd() runs
+ * and establishes a child pmd before
+ * __split_huge_page_splitting() freezes the parent pmd (so if
+ * we fail to prevent copy_huge_pmd() from running until the
+ * whole __split_huge_page() is complete), we will still see
+ * the newly established pmd of the child later during the
+ * walk, to be able to set it as pmd_trans_splitting too.
+ */
+ if (mapcount != page_mapcount(page))
+ printk(KERN_ERR "mapcount %d page_mapcount %d\n",
+ mapcount, page_mapcount(page));
BUG_ON(mapcount != page_mapcount(page));
__split_huge_page_refcount(page);
@@ -854,6 +867,9 @@ static void __split_huge_page(struct pag
continue;
mapcount2 += __split_huge_page_map(page, vma, addr);
}
+ if (mapcount != mapcount2)
+ printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
+ mapcount, mapcount2, page_mapcount(page));
BUG_ON(mapcount != mapcount2);
}
diff -puN mm/rmap.c~thp-split_huge_page-anon_vma-ordering-dependency mm/rmap.c
--- a/mm/rmap.c~thp-split_huge_page-anon_vma-ordering-dependency
+++ a/mm/rmap.c
@@ -177,6 +177,10 @@ static void anon_vma_chain_link(struct v
list_add(&avc->same_vma, &vma->anon_vma_chain);
anon_vma_lock(anon_vma);
+ /*
+ * It's critical to add new vmas to the tail of the anon_vma,
+ * see comment in huge_memory.c:__split_huge_page().
+ */
list_add_tail(&avc->same_anon_vma, &anon_vma->head);
anon_vma_unlock(anon_vma);
}
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
origin.patch
thp-add-pagetranscompound.patch
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