memcg: move charge of file pages

This patch adds support for moving charge of file pages, which include
normal file, tmpfs file and swaps of tmpfs file.  It's enabled by setting
bit 1 of <target cgroup>/memory.move_charge_at_immigrate.

Unlike the case of anonymous pages, file pages(and swaps) in the range
mmapped by the task will be moved even if the task hasn't done page fault,
i.e.  they might not be the task's "RSS", but other task's "RSS" that maps
the same file.  And mapcount of the page is ignored(the page can be moved
even if page_mapcount(page) > 1).  So, conditions that the page/swap
should be met to be moved is that it must be in the range mmapped by the
target task and it must be charged to the old cgroup.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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>

2 files changed, 108 insertions, 12 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e5277e8..be5f478 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -250,6 +250,7 @@ struct mem_cgroup {
  */
 enum move_type {
 	MOVE_CHARGE_TYPE_ANON,	/* private anonymous page and swap of it */
+	MOVE_CHARGE_TYPE_FILE,	/* file page(including tmpfs) and swap of it */
 	NR_MOVE_TYPE,
 };
 
@@ -272,6 +273,12 @@ static bool move_anon(void)
 					&mc.to->move_charge_at_immigrate);
 }
 
+static bool move_file(void)
+{
+	return test_bit(MOVE_CHARGE_TYPE_FILE,
+					&mc.to->move_charge_at_immigrate);
+}
+
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
@@ -4179,11 +4186,8 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
 		/* we don't move shared anon */
 		if (!move_anon() || page_mapcount(page) > 2)
 			return NULL;
-	} else
-		/*
-		 * TODO: We don't move charges of file(including shmem/tmpfs)
-		 * pages for now.
-		 */
+	} else if (!move_file())
+		/* we ignore mapcount for file pages */
 		return NULL;
 	if (!get_page_unless_zero(page))
 		return NULL;
@@ -4212,6 +4216,39 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
 	return page;
 }
 
+static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
+			unsigned long addr, pte_t ptent, swp_entry_t *entry)
+{
+	struct page *page = NULL;
+	struct inode *inode;
+	struct address_space *mapping;
+	pgoff_t pgoff;
+
+	if (!vma->vm_file) /* anonymous vma */
+		return NULL;
+	if (!move_file())
+		return NULL;
+
+	inode = vma->vm_file->f_path.dentry->d_inode;
+	mapping = vma->vm_file->f_mapping;
+	if (pte_none(ptent))
+		pgoff = linear_page_index(vma, addr);
+	else /* pte_file(ptent) is true */
+		pgoff = pte_to_pgoff(ptent);
+
+	/* page is moved even if it's not RSS of this task(page-faulted). */
+	if (!mapping_cap_swap_backed(mapping)) { /* normal file */
+		page = find_get_page(mapping, pgoff);
+	} else { /* shmem/tmpfs file. we should take account of swap too. */
+		swp_entry_t ent;
+		mem_cgroup_get_shmem_target(inode, pgoff, &page, &ent);
+		if (do_swap_account)
+			entry->val = ent.val;
+	}
+
+	return page;
+}
+
 static int is_target_pte_for_mc(struct vm_area_struct *vma,
 		unsigned long addr, pte_t ptent, union mc_target *target)
 {
@@ -4224,7 +4261,8 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
 		page = mc_handle_present_pte(vma, addr, ptent);
 	else if (is_swap_pte(ptent))
 		page = mc_handle_swap_pte(vma, addr, ptent, &ent);
-	/* TODO: handle swap of shmes/tmpfs */
+	else if (pte_none(ptent) || pte_file(ptent))
+		page = mc_handle_file_pte(vma, addr, ptent, &ent);
 
 	if (!page && !ent.val)
 		return 0;
@@ -4285,9 +4323,6 @@ static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
 		};
 		if (is_vm_hugetlb_page(vma))
 			continue;
-		/* TODO: We don't move charges of shmem/tmpfs pages for now. */
-		if (vma->vm_flags & VM_SHARED)
-			continue;
 		walk_page_range(vma->vm_start, vma->vm_end,
 					&mem_cgroup_count_precharge_walk);
 	}
@@ -4484,9 +4519,6 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
 		};
 		if (is_vm_hugetlb_page(vma))
 			continue;
-		/* TODO: We don't move charges of shmem/tmpfs pages for now. */
-		if (vma->vm_flags & VM_SHARED)
-			continue;
 		ret = walk_page_range(vma->vm_start, vma->vm_end,
 						&mem_cgroup_move_charge_walk);
 		if (ret)
diff --git a/mm/shmem.c b/mm/shmem.c
index 4ef9797..855eaf5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2559,6 +2559,45 @@ out4:
 	return error;
 }
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+/**
+ * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
+ * @inode: the inode to be searched
+ * @pgoff: the offset to be searched
+ * @pagep: the pointer for the found page to be stored
+ * @ent: the pointer for the found swap entry to be stored
+ *
+ * If a page is found, refcount of it is incremented. Callers should handle
+ * these refcount.
+ */
+void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
+					struct page **pagep, swp_entry_t *ent)
+{
+	swp_entry_t entry = { .val = 0 }, *ptr;
+	struct page *page = NULL;
+	struct shmem_inode_info *info = SHMEM_I(inode);
+
+	if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
+		goto out;
+
+	spin_lock(&info->lock);
+	ptr = shmem_swp_entry(info, pgoff, NULL);
+#ifdef CONFIG_SWAP
+	if (ptr && ptr->val) {
+		entry.val = ptr->val;
+		page = find_get_page(&swapper_space, entry.val);
+	} else
+#endif
+		page = find_get_page(inode->i_mapping, pgoff);
+	if (ptr)
+		shmem_swp_unmap(ptr);
+	spin_unlock(&info->lock);
+out:
+	*pagep = page;
+	*ent = entry;
+}
+#endif
+
 #else /* !CONFIG_SHMEM */
 
 /*
@@ -2598,6 +2637,31 @@ int shmem_lock(struct file *file, int lock, struct user_struct *user)
 	return 0;
 }
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+/**
+ * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
+ * @inode: the inode to be searched
+ * @pgoff: the offset to be searched
+ * @pagep: the pointer for the found page to be stored
+ * @ent: the pointer for the found swap entry to be stored
+ *
+ * If a page is found, refcount of it is incremented. Callers should handle
+ * these refcount.
+ */
+void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
+					struct page **pagep, swp_entry_t *ent)
+{
+	struct page *page = NULL;
+
+	if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
+		goto out;
+	page = find_get_page(inode->i_mapping, pgoff);
+out:
+	*pagep = page;
+	*ent = (swp_entry_t){ .val = 0 };
+}
+#endif
+
 #define shmem_vm_ops				generic_file_vm_ops
 #define shmem_file_operations			ramfs_file_operations
 #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)