Keep track of the inodes that have been dirtied by each blkcg cgroup and
make sure that a blkcg issuing a sync() can trigger the writeback + wait
of only those pages that belong to the cgroup itself.
This behavior is applied only when io.sync_isolation is enabled in the
cgroup, otherwise the old behavior is applied: sync() triggers the
writeback of any dirty page.
Signed-off-by: Andrea Righi <andrea.ri...@canonical.com>
---
block/blk-cgroup.c | 47 ++++++++++++++++++++++++++++++++++
fs/fs-writeback.c | 52 +++++++++++++++++++++++++++++++++++---
fs/inode.c | 1 +
include/linux/blk-cgroup.h | 22 ++++++++++++++++
include/linux/fs.h | 4 +++
mm/page-writeback.c | 1 +
6 files changed, 124 insertions(+), 3 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 4305e78d1bb2..7d3b26ba4575 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1480,6 +1480,53 @@ void blkcg_stop_wb_wait_on_bdi(struct backing_dev_info
*bdi)
spin_unlock(&blkcg_wb_sleeper_lock);
rcu_read_unlock();
}
+
+/**
+ * blkcg_set_mapping_dirty - set owner of a dirty mapping
+ * @mapping: target address space
+ *
+ * Set the current blkcg as the owner of the address space @mapping (the first
+ * blkcg that dirties @mapping becomes the owner).
+ */
+void blkcg_set_mapping_dirty(struct address_space *mapping)
+{
+ struct blkcg *curr_blkcg, *blkcg;
+
+ if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK) ||
+ mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+ return;
+
+ rcu_read_lock();
+ curr_blkcg = blkcg_from_current();
+ blkcg = blkcg_from_mapping(mapping);
+ if (curr_blkcg != blkcg) {
+ if (blkcg)
+ css_put(&blkcg->css);
+ css_get(&curr_blkcg->css);
+ rcu_assign_pointer(mapping->i_blkcg, curr_blkcg);
+ }
+ rcu_read_unlock();
+}
+
+/**
+ * blkcg_set_mapping_clean - clear the owner of a dirty mapping
+ * @mapping: target address space
+ *
+ * Unset the owner of @mapping when it becomes clean.
+ */
+
+void blkcg_set_mapping_clean(struct address_space *mapping)
+{
+ struct blkcg *blkcg;
+
+ rcu_read_lock();
+ blkcg = rcu_dereference(mapping->i_blkcg);
+ if (blkcg) {
+ css_put(&blkcg->css);
+ RCU_INIT_POINTER(mapping->i_blkcg, NULL);
+ }
+ rcu_read_unlock();
+}
#endif
/**
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 77c039a0ec25..d003d0593f41 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -58,6 +58,9 @@ struct wb_writeback_work {
struct list_head list; /* pending work list */
struct wb_completion *done; /* set if the caller waits */
+#ifdef CONFIG_CGROUP_WRITEBACK
+ struct blkcg *blkcg;
+#endif
};
/*
@@ -916,6 +919,29 @@ static int __init cgroup_writeback_init(void)
}
fs_initcall(cgroup_writeback_init);
+static void blkcg_set_sync_domain(struct wb_writeback_work *work)
+{
+ rcu_read_lock();
+ work->blkcg = blkcg_from_current();
+ rcu_read_unlock();
+}
+
+static bool blkcg_same_sync_domain(struct wb_writeback_work *work,
+ struct address_space *mapping)
+{
+ struct blkcg *blkcg;
+
+ if (!work->blkcg || work->blkcg == &blkcg_root)
+ return true;
+ if (!test_bit(BLKCG_SYNC_ISOLATION, &work->blkcg->flags))
+ return true;
+ rcu_read_lock();
+ blkcg = blkcg_from_mapping(mapping);
+ rcu_read_unlock();
+
+ return blkcg == work->blkcg;
+}
+
#else /* CONFIG_CGROUP_WRITEBACK */
static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
@@ -959,6 +985,15 @@ static void bdi_split_work_to_wbs(struct backing_dev_info
*bdi,
}
}
+static void blkcg_set_sync_domain(struct wb_writeback_work *work)
+{
+}
+
+static bool blkcg_same_sync_domain(struct wb_writeback_work *work,
+ struct address_space *mapping)
+{
+ return true;
+}
#endif /* CONFIG_CGROUP_WRITEBACK */
/*
@@ -1131,7 +1166,7 @@ static int move_expired_inodes(struct list_head
*delaying_queue,
LIST_HEAD(tmp);
struct list_head *pos, *node;
struct super_block *sb = NULL;
- struct inode *inode;
+ struct inode *inode, *next;
int do_sb_sort = 0;
int moved = 0;
@@ -1141,11 +1176,12 @@ static int move_expired_inodes(struct list_head
*delaying_queue,
expire_time = jiffies - (dirtytime_expire_interval * HZ);
older_than_this = &expire_time;
}
- while (!list_empty(delaying_queue)) {
- inode = wb_inode(delaying_queue->prev);
+ list_for_each_entry_safe(inode, next, delaying_queue, i_io_list) {
if (older_than_this &&
inode_dirtied_after(inode, *older_than_this))
break;
+ if (!blkcg_same_sync_domain(work, inode->i_mapping))
+ continue;
list_move(&inode->i_io_list, &tmp);
moved++;
if (flags & EXPIRE_DIRTY_ATIME)
@@ -1560,6 +1596,15 @@ static long writeback_sb_inodes(struct super_block *sb,
break;
}
+ /*
+ * Only write out inodes that belong to the blkcg that issued
+ * the sync().
+ */
+ if (!blkcg_same_sync_domain(work, inode->i_mapping)) {
+ redirty_tail(inode, wb);
+ continue;
+ }
+
/*
* Don't bother with new inodes or inodes being freed, first
* kind does not need periodic writeout yet, and for the latter
@@ -2447,6 +2492,7 @@ void sync_inodes_sb(struct super_block *sb)
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
+ blkcg_set_sync_domain(&work);
blkcg_start_wb_wait_on_bdi(bdi);
/* protect against inode wb switch, see inode_switch_wbs_work_fn() */
diff --git a/fs/inode.c b/fs/inode.c
index e9d97add2b36..b9659aaa8546 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -564,6 +564,7 @@ static void evict(struct inode *inode)
bd_forget(inode);
if (S_ISCHR(inode->i_mode) && inode->i_cdev)
cd_forget(inode);
+ blkcg_set_mapping_clean(&inode->i_data);
remove_inode_hash(inode);
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 6ac5aa049334..a2bcc83c8c3e 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -441,6 +441,15 @@ extern void blkcg_destroy_blkgs(struct blkcg *blkcg);
#ifdef CONFIG_CGROUP_WRITEBACK
+static inline struct blkcg *blkcg_from_mapping(struct address_space *mapping)
+{
+ WARN_ON_ONCE(!rcu_read_lock_held());
+ return rcu_dereference(mapping->i_blkcg);
+}
+
+void blkcg_set_mapping_dirty(struct address_space *mapping);
+void blkcg_set_mapping_clean(struct address_space *mapping);
+
/**
* blkcg_cgwb_get - get a reference for blkcg->cgwb_list
* @blkcg: blkcg of interest
@@ -474,6 +483,19 @@ void blkcg_stop_wb_wait_on_bdi(struct backing_dev_info
*bdi);
#else
+static inline struct blkcg *blkcg_from_mapping(struct address_space *mapping)
+{
+ return NULL;
+}
+
+static inline void blkcg_set_mapping_dirty(struct address_space *mapping)
+{
+}
+
+static inline void blkcg_set_mapping_clean(struct address_space *mapping)
+{
+}
+
static inline void blkcg_cgwb_get(struct blkcg *blkcg) { }
static inline void blkcg_cgwb_put(struct blkcg *blkcg)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 08f26046233e..19e99b4a9fa2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -420,6 +420,7 @@ int pagecache_write_end(struct file *, struct address_space
*mapping,
* @nrpages: Number of page entries, protected by the i_pages lock.
* @nrexceptional: Shadow or DAX entries, protected by the i_pages lock.
* @writeback_index: Writeback starts here.
+ * @i_blkcg: blkcg owner (that dirtied the address_space)
* @a_ops: Methods.
* @flags: Error bits and flags (AS_*).
* @wb_err: The most recent error which has occurred.
@@ -438,6 +439,9 @@ struct address_space {
unsigned long nrexceptional;
pgoff_t writeback_index;
const struct address_space_operations *a_ops;
+#ifdef CONFIG_CGROUP_WRITEBACK
+ struct blkcg __rcu *i_blkcg;
+#endif
unsigned long flags;
errseq_t wb_err;
spinlock_t private_lock;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9f61dfec6a1f..e16574f946a7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2418,6 +2418,7 @@ void account_page_dirtied(struct page *page, struct
address_space *mapping)
inode_attach_wb(inode, page);
wb = inode_to_wb(inode);
+ blkcg_set_mapping_dirty(mapping);
__inc_lruvec_page_state(page, NR_FILE_DIRTY);
__inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
__inc_node_page_state(page, NR_DIRTIED);
--
2.19.1
