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authorHugh Dickins <hugh@veritas.com>2008-03-04 14:29:06 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:14 -0800
commit98837c7f82ef78aa38f40462aa2fcac68fd3acbf (patch)
tree6d76841b18b57a9202d7699ba4dca5b39fdd7aea /include
parent61469f1d51777fc3b6d8d70da8373ee77ee13349 (diff)
memcg: fix VM_BUG_ON from page migration
Page migration gave me free_hot_cold_page's VM_BUG_ON page->page_cgroup. remove_migration_pte was calling mem_cgroup_charge on the new page whenever it found a swap pte, before it had determined it to be a migration entry. That left a surplus reference count on the page_cgroup, so it was still attached when the page was later freed. Move that mem_cgroup_charge down to where we're sure it's a migration entry. We were already under i_mmap_lock or anon_vma->lock, so its GFP_KERNEL was already inappropriate: change that to GFP_ATOMIC. It's essential that remove_migration_pte removes all the migration entries, other crashes follow if not. So proceed even when the charge fails: normally it cannot, but after a mem_cgroup_force_empty it might - comment in the code. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: David Rientjes <rientjes@google.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hirokazu Takahashi <taka@valinux.co.jp> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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