This patch add a member to swap_info_struct for cgroup.

This member, array of pointers to mem_cgroup, is used to
remember to which cgroup each swap entries are charged.

The memory for this array of pointers is allocated on swapon,
and freed on swapoff.


Change log
v2->v3
- Rebased on 2.6.26-rc5-mm3
- add helper functions and removed #ifdef from sys_swapon()/sys_swapoff().
- add check on mem_cgroup_subsys.disabled
v1->v2
- Rebased on 2.6.26-rc2-mm1
- Implemented as a add-on to memory cgroup.


Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

---
 include/linux/memcontrol.h |   20 +++++++++++++++++++-
 include/linux/swap.h       |    3 +++
 mm/memcontrol.c            |   36 ++++++++++++++++++++++++++++++++++++
 mm/swapfile.c              |   11 +++++++++++
 4 files changed, 69 insertions(+), 1 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ee1b2fc..b6ff509 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -24,6 +24,7 @@ struct mem_cgroup;
 struct page_cgroup;
 struct page;
 struct mm_struct;
+struct swap_info_struct;
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 
@@ -165,5 +166,22 @@ static inline long mem_cgroup_calc_reclaim(struct mem_cgroup *mem,
 }
 #endif /* CONFIG_CGROUP_MEM_CONT */
 
-#endif /* _LINUX_MEMCONTROL_H */
+#ifdef CONFIG_CGROUP_SWAP_RES_CTLR
+extern struct mem_cgroup **swap_info_clear_memcg(struct swap_info_struct *p);
+extern int swap_info_alloc_memcg(struct swap_info_struct *p,
+				unsigned long maxpages);
+#else
+static inline
+struct mem_cgroup **swap_info_clear_memcg(struct swap_info_struct *p)
+{
+	return NULL;
+}
 
+static inline
+int swap_info_alloc_memcg(struct swap_info_struct *p, unsigned long maxpages)
+{
+	return 0;
+}
+#endif
+
+#endif /* _LINUX_MEMCONTROL_H */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index a3af95b..6e1b03d 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -142,6 +142,9 @@ struct swap_info_struct {
 	struct swap_extent *curr_swap_extent;
 	unsigned old_block_size;
 	unsigned short * swap_map;
+#ifdef CONFIG_CGROUP_SWAP_RES_CTLR
+	struct mem_cgroup **memcg;
+#endif
 	unsigned int lowest_bit;
 	unsigned int highest_bit;
 	unsigned int cluster_next;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ddc842b..81bb7fa 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1209,3 +1209,39 @@ struct cgroup_subsys mem_cgroup_subsys = {
 	.attach = mem_cgroup_move_task,
 	.early_init = 0,
 };
+
+#ifdef CONFIG_CGROUP_SWAP_RES_CTLR
+/* called with swap_lock held */
+struct mem_cgroup **swap_info_clear_memcg(struct swap_info_struct *p)
+{
+	struct mem_cgroup **mem;
+
+	/* just clear p->memcg, without checking mem_cgroup_subsys.disabled */
+	mem = p->memcg;
+	p->memcg = NULL;
+
+	return mem;
+}
+
+/* called without swap_lock held */
+int swap_info_alloc_memcg(struct swap_info_struct *p, unsigned long maxpages)
+{
+	int ret = 0;
+
+	if (mem_cgroup_subsys.disabled)
+		goto out;
+
+	p->memcg = vmalloc(maxpages * sizeof(struct mem_cgroup *));
+	if (!p->memcg) {
+		/* make swapon fail */
+		printk(KERN_ERR "Unable to allocate memory for memcg\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+	memset(p->memcg, 0, maxpages * sizeof(struct mem_cgroup *));
+
+out:
+	return ret;
+}
+#endif
+
diff --git a/mm/swapfile.c b/mm/swapfile.c
index bf7d13d..312c573 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1228,6 +1228,7 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
 	unsigned short *swap_map;
 	struct file *swap_file, *victim;
 	struct address_space *mapping;
+	struct mem_cgroup **memcg = NULL;
 	struct inode *inode;
 	char * pathname;
 	int i, type, prev;
@@ -1328,10 +1329,12 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
 	p->max = 0;
 	swap_map = p->swap_map;
 	p->swap_map = NULL;
+	memcg = swap_info_clear_memcg(p);
 	p->flags = 0;
 	spin_unlock(&swap_lock);
 	mutex_unlock(&swapon_mutex);
 	vfree(swap_map);
+	vfree(memcg);
 	inode = mapping->host;
 	if (S_ISBLK(inode->i_mode)) {
 		struct block_device *bdev = I_BDEV(inode);
@@ -1475,6 +1478,7 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 	unsigned long maxpages = 1;
 	int swapfilesize;
 	unsigned short *swap_map;
+	struct mem_cgroup **memcg = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
 	int did_down = 0;
@@ -1498,6 +1502,7 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 	p->swap_file = NULL;
 	p->old_block_size = 0;
 	p->swap_map = NULL;
+	swap_info_clear_memcg(p);
 	p->lowest_bit = 0;
 	p->highest_bit = 0;
 	p->cluster_nr = 0;
@@ -1670,6 +1675,10 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 				1 /* header page */;
 		if (error)
 			goto bad_swap;
+
+		error = swap_info_alloc_memcg(p, maxpages);
+		if (error)
+			goto bad_swap;
 	}
 
 	if (nr_good_pages) {
@@ -1729,11 +1738,13 @@ bad_swap_2:
 	swap_map = p->swap_map;
 	p->swap_file = NULL;
 	p->swap_map = NULL;
+	memcg = swap_info_clear_memcg(p);
 	p->flags = 0;
 	if (!(swap_flags & SWAP_FLAG_PREFER))
 		++least_priority;
 	spin_unlock(&swap_lock);
 	vfree(swap_map);
+	vfree(memcg);
 	if (swap_file)
 		filp_close(swap_file, NULL);
 out:
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