On Tue, Dec 25 2012, Sha Zhengju wrote:
> From: Sha Zhengju <handai.szj@xxxxxxxxxx>
>
> Similar to dirty page, we add per cgroup writeback pages accounting. The lock
> rule still is:
> mem_cgroup_begin_update_page_stat()
> modify page WRITEBACK stat
> mem_cgroup_update_page_stat()
> mem_cgroup_end_update_page_stat()
>
> There're two writeback interface to modify: test_clear/set_page_writeback.
>
> Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 1 +
> mm/memcontrol.c | 5 +++++
> mm/page-writeback.c | 17 +++++++++++++++++
> 3 files changed, 23 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 358019e..1d22b81 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -45,6 +45,7 @@ enum mem_cgroup_stat_index {
> MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
> MEM_CGROUP_STAT_SWAP, /* # of pages, swapped out */
> MEM_CGROUP_STAT_FILE_DIRTY, /* # of dirty pages in page cache */
> + MEM_CGROUP_STAT_WRITEBACK, /* # of pages under writeback */
> MEM_CGROUP_STAT_NSTATS,
> };
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 21df36d..13cd14a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -96,6 +96,7 @@ static const char * const mem_cgroup_stat_names[] = {
> "mapped_file",
> "swap",
> "dirty",
> + "writeback",
> };
>
> enum mem_cgroup_events_index {
> @@ -3676,6 +3677,10 @@ static int mem_cgroup_move_account(struct page *page,
> mem_cgroup_move_account_page_stat(from, to, nr_pages,
> MEM_CGROUP_STAT_FILE_DIRTY);
>
> + if (PageWriteback(page))
> + mem_cgroup_move_account_page_stat(from, to, nr_pages,
> + MEM_CGROUP_STAT_WRITEBACK);
> +
> mem_cgroup_charge_statistics(from, anon, -nr_pages);
>
> /* caller should have done css_get */
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 526ddd7..ae6498a 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2002,11 +2002,17 @@ EXPORT_SYMBOL(account_page_dirtied);
>
> /*
> * Helper function for set_page_writeback family.
> + *
> + * The caller must hold mem_cgroup_begin/end_update_page_stat() lock
> + * while modifying struct page state and accounting writeback pages.
> + * See test_set_page_writeback for example.
> + *
> * NOTE: Unlike account_page_dirtied this does not rely on being atomic
> * wrt interrupts.
> */
> void account_page_writeback(struct page *page)
> {
> + mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
> inc_zone_page_state(page, NR_WRITEBACK);
> }
> EXPORT_SYMBOL(account_page_writeback);
> @@ -2242,7 +2248,10 @@ int test_clear_page_writeback(struct page *page)
> {
> struct address_space *mapping = page_mapping(page);
> int ret;
> + bool locked;
> + unsigned long memcg_flags;
>
> + mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags);
Does this violate lock ordering? Here we are grabbing
mem_cgroup_begin_update_page_stat and below we grab tree_lock. I
thought the prescribed order was tree_lock first, then
mem_cgroup_begin_update_page_stat.
> if (mapping) {
> struct backing_dev_info *bdi = mapping->backing_dev_info;
> unsigned long flags;
> @@ -2263,9 +2272,12 @@ int test_clear_page_writeback(struct page *page)
> ret = TestClearPageWriteback(page);
> }
> if (ret) {
> + mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
> dec_zone_page_state(page, NR_WRITEBACK);
> inc_zone_page_state(page, NR_WRITTEN);
> }
> +
> + mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
> return ret;
> }
>
> @@ -2273,7 +2285,10 @@ int test_set_page_writeback(struct page *page)
> {
> struct address_space *mapping = page_mapping(page);
> int ret;
> + bool locked;
> + unsigned long flags;
>
> + mem_cgroup_begin_update_page_stat(page, &locked, &flags);
Same "Does this violate lock ordering?" question as above.
> if (mapping) {
> struct backing_dev_info *bdi = mapping->backing_dev_info;
> unsigned long flags;
> @@ -2300,6 +2315,8 @@ int test_set_page_writeback(struct page *page)
> }
> if (!ret)
> account_page_writeback(page);
> +
> + mem_cgroup_end_update_page_stat(page, &locked, &flags);
> return ret;
>
> }
--
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