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memcg: fix race at move_parent around compound_order()
A fix up mem_cgroup_move_parent() which use compound_order() in asynchronous manner. This compound_order() may return unknown value because we don't take lock. Use PageTransHuge() and HPAGE_SIZE instead of it. Also clean up for mem_cgroup_move_parent(). - remove unnecessary initialization of local variable. - rename charge_size -> page_size - remove unnecessary (wrong) comment. - added a comment about THP. Note: Current design take compound_page_lock() in caller of move_account(). This should be revisited when we implement direct move_task of hugepage without splitting. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
3d37c4a919
commit
52dbb90509
1 changed files with 16 additions and 9 deletions
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@ -2236,7 +2236,12 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
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{
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{
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int ret = -EINVAL;
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int ret = -EINVAL;
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unsigned long flags;
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unsigned long flags;
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/*
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* The page is isolated from LRU. So, collapse function
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* will not handle this page. But page splitting can happen.
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* Do this check under compound_page_lock(). The caller should
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* hold it.
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*/
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if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page))
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if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page))
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return -EBUSY;
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return -EBUSY;
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@ -2268,7 +2273,7 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
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struct cgroup *cg = child->css.cgroup;
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struct cgroup *cg = child->css.cgroup;
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struct cgroup *pcg = cg->parent;
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struct cgroup *pcg = cg->parent;
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struct mem_cgroup *parent;
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struct mem_cgroup *parent;
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int charge = PAGE_SIZE;
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int page_size = PAGE_SIZE;
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unsigned long flags;
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unsigned long flags;
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int ret;
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int ret;
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@ -2281,22 +2286,24 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
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goto out;
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goto out;
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if (isolate_lru_page(page))
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if (isolate_lru_page(page))
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goto put;
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goto put;
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/* The page is isolated from LRU and we have no race with splitting */
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charge = PAGE_SIZE << compound_order(page);
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if (PageTransHuge(page))
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page_size = HPAGE_SIZE;
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parent = mem_cgroup_from_cont(pcg);
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parent = mem_cgroup_from_cont(pcg);
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ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, charge);
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ret = __mem_cgroup_try_charge(NULL, gfp_mask,
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&parent, false, page_size);
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if (ret || !parent)
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if (ret || !parent)
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goto put_back;
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goto put_back;
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if (charge > PAGE_SIZE)
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if (page_size > PAGE_SIZE)
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flags = compound_lock_irqsave(page);
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flags = compound_lock_irqsave(page);
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ret = mem_cgroup_move_account(pc, child, parent, true, charge);
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ret = mem_cgroup_move_account(pc, child, parent, true, page_size);
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if (ret)
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if (ret)
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mem_cgroup_cancel_charge(parent, charge);
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mem_cgroup_cancel_charge(parent, page_size);
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if (charge > PAGE_SIZE)
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if (page_size > PAGE_SIZE)
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compound_unlock_irqrestore(page, flags);
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compound_unlock_irqrestore(page, flags);
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put_back:
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put_back:
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putback_lru_page(page);
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putback_lru_page(page);
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