We now have slub's ->freelist usage impinging on page->mapping's
storage space. The buddy allocator wants ->mapping to be NULL
when a page is handed back, so we have to make sure that it is
cleared.
Note that slab already doeds this, so just create a common helper
and have all the slabs do it this way. ->mapping is right next
to ->flags, so it's virtually guaranteed to be in the L1 at this
point, so this shouldn't cost very much to do in practice.
---
linux.git-davehans/mm/slab.c | 3 +--
linux.git-davehans/mm/slab.h | 11 +++++++++++
linux.git-davehans/mm/slob.c | 2 +-
linux.git-davehans/mm/slub.c | 2 +-
4 files changed, 14 insertions(+), 4 deletions(-)
diff -puN mm/slab.c~slub-reset-page-at-free mm/slab.c
--- linux.git/mm/slab.c~slub-reset-page-at-free 2013-12-11 13:19:55.026994096 -0800
+++ linux.git-davehans/mm/slab.c 2013-12-11 13:19:55.036994538 -0800
@@ -1725,8 +1725,7 @@ static void kmem_freepages(struct kmem_c
BUG_ON(!PageSlab(page));
__ClearPageSlabPfmemalloc(page);
__ClearPageSlab(page);
- page_mapcount_reset(page);
- page->mapping = NULL;
+ slab_reset_page(page);
memcg_release_pages(cachep, cachep->gfporder);
if (current->reclaim_state)
diff -puN mm/slab.h~slub-reset-page-at-free mm/slab.h
--- linux.git/mm/slab.h~slub-reset-page-at-free 2013-12-11 13:19:55.028994185 -0800
+++ linux.git-davehans/mm/slab.h 2013-12-11 13:19:55.036994538 -0800
@@ -279,3 +279,14 @@ struct kmem_cache_node {
void *slab_next(struct seq_file *m, void *p, loff_t *pos);
void slab_stop(struct seq_file *m, void *p);
+/*
+ * The slab allocators use 'struct page' fields for all kinds of
+ * things. This resets the page so that the buddy allocator will
+ * be happy with it.
+ */
+static inline void slab_reset_page(struct page *page)
+{
+ page->mapping = NULL;
+ page_mapcount_reset(page);
+}
+
diff -puN mm/slob.c~slub-reset-page-at-free mm/slob.c
--- linux.git/mm/slob.c~slub-reset-page-at-free 2013-12-11 13:19:55.029994229 -0800
+++ linux.git-davehans/mm/slob.c 2013-12-11 13:19:55.036994538 -0800
@@ -371,7 +371,7 @@ static void slob_free(void *block, int s
clear_slob_page_free(sp);
spin_unlock_irqrestore(&slob_lock, flags);
__ClearPageSlab((struct page *)sp);
- page_mapcount_reset((struct page *)sp);
+ slab_reset_page((struct page *)sp);
slob_free_pages(b, 0);
return;
}
diff -puN mm/slub.c~slub-reset-page-at-free mm/slub.c
--- linux.git/mm/slub.c~slub-reset-page-at-free 2013-12-11 13:19:55.031994317 -0800
+++ linux.git-davehans/mm/slub.c 2013-12-11 13:19:55.039994671 -0800
@@ -1530,7 +1530,7 @@ static void __free_slab(struct kmem_cach
__ClearPageSlab(page);
memcg_release_pages(s, order);
- page_mapcount_reset(page);
+ slab_reset_page(page);
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab += pages;
__free_memcg_kmem_pages(page, order);
_
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