[PATCH 21/49] writeback: add {CONFIG|BDI_CAP|FS}_CGROUP_WRITEBACK

Tejun Heo
2015-04-06T20:18:11Z

cgroup writeback requires support from both bdi and filesystem sides.
Add BDI_CAP_CGROUP_WRITEBACK and FS_CGROUP_WRITEBACK to indicate
support and enable BDI_CAP_CGROUP_WRITEBACK on block based bdi's by
default. Also, define CONFIG_CGROUP_WRITEBACK which is enabled if
both MEMCG and BLK_CGROUP are enabled.

inode_cgwb_enabled() which determines whether a given inode's both bdi
and fs support cgroup writeback is added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
---
block/blk-core.c | 2 +-
include/linux/backing-dev.h | 32 +++++++++++++++++++++++++++++++-
include/linux/fs.h | 1 +
init/Kconfig | 5 +++++
4 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index fa1314e..c44018a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -606,7 +606,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)

q->backing_dev_info.ra_pages =
(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
- q->backing_dev_info.capabilities = 0;
+ q->backing_dev_info.capabilities = BDI_CAP_CGROUP_WRITEBACK;
q->backing_dev_info.name = "block";
q->node = node_id;

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index bfdaa18..6bb3123 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -134,12 +134,15 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
* BDI_CAP_NO_WRITEBACK: Don't write pages back
* BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
* BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
+ *
+ * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
*/
#define BDI_CAP_NO_ACCT_DIRTY 0x00000001
#define BDI_CAP_NO_WRITEBACK 0x00000002
#define BDI_CAP_NO_ACCT_WB 0x00000004
#define BDI_CAP_STABLE_WRITES 0x00000008
#define BDI_CAP_STRICTLIMIT 0x00000010
+#define BDI_CAP_CGROUP_WRITEBACK 0x00000020

#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
@@ -229,4 +232,31 @@ static inline int bdi_sched_wait(void *word)
return 0;
}

-#endif /* _LINUX_BACKING_DEV_H */
+#ifdef CONFIG_CGROUP_WRITEBACK
+
+/**
+ * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
+ * @inode: inode of interest
+ *
+ * cgroup writeback requires support from both the bdi and filesystem.
+ * Test whether @inode has both.
+ */
+static inline bool inode_cgwb_enabled(struct inode *inode)
+{
+ struct backing_dev_info *bdi = inode_to_bdi(inode);
+
+ return bdi_cap_account_dirty(bdi) &&
+ (bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
+ (inode->i_sb->s_type->fs_flags & FS_CGROUP_WRITEBACK);
+}
+
+#else /* CONFIG_CGROUP_WRITEBACK */
+
+static inline bool inode_cgwb_enabled(struct inode *inode)
+{
+ return false;
+}
+
+#endif /* CONFIG_CGROUP_WRITEBACK */
+
+#endif /* _LINUX_BACKING_DEV_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ccf4b64..bc72737 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1862,6 +1862,7 @@ struct file_system_type {
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
+#define FS_CGROUP_WRITEBACK 32 /* Supports cgroup-aware writeback */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);
diff --git a/init/Kconfig b/init/Kconfig
index f5dbc6d..9f17798 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1132,6 +1132,11 @@ config DEBUG_BLK_CGROUP
Enable some debugging help. Currently it exports additional stat
files in a cgroup which can be useful for debugging.

+config CGROUP_WRITEBACK
+ bool
+ depends on MEMCG && BLK_CGROUP
+ default y
+
endif # CGROUPS

config CHECKPOINT_RESTORE
--
2.1.0