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writeback: implement bdi_for_each_wb() 

This will be used to implement bdi-wide operations which should be
distributed across all its cgroup bdi_writebacks.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-05-22 17:13:50 -04:00 committed by Jens Axboe
parent 693108a8a6
commit ebe41ab0c7
1 changed files with 63 additions and 0 deletions
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63
include/linux/backing-dev.h
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@ -383,6 +383,61 @@ static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
return inode->i_wb;
}
struct wb_iter {
int start_blkcg_id;
struct radix_tree_iter tree_iter;
void **slot;
};
static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *iter,
struct backing_dev_info *bdi)
{
struct radix_tree_iter *titer = &iter->tree_iter;
WARN_ON_ONCE(!rcu_read_lock_held());
if (iter->start_blkcg_id >= 0) {
iter->slot = radix_tree_iter_init(titer, iter->start_blkcg_id);
iter->start_blkcg_id = -1;
} else {
iter->slot = radix_tree_next_slot(iter->slot, titer, 0);
}
if (!iter->slot)
iter->slot = radix_tree_next_chunk(&bdi->cgwb_tree, titer, 0);
if (iter->slot)
return *iter->slot;
return NULL;
}
static inline struct bdi_writeback *__wb_iter_init(struct wb_iter *iter,
struct backing_dev_info *bdi,
int start_blkcg_id)
{
iter->start_blkcg_id = start_blkcg_id;
if (start_blkcg_id)
return __wb_iter_next(iter, bdi);
else
return &bdi->wb;
}
/**
* bdi_for_each_wb - walk all wb's of a bdi in ascending blkcg ID order
* @wb_cur: cursor struct bdi_writeback pointer
* @bdi: bdi to walk wb's of
* @iter: pointer to struct wb_iter to be used as iteration buffer
* @start_blkcg_id: blkcg ID to start iteration from
*
* Iterate @wb_cur through the wb's (bdi_writeback's) of @bdi in ascending
* blkcg ID order starting from @start_blkcg_id. @iter is struct wb_iter
* to be used as temp storage during iteration. rcu_read_lock() must be
* held throughout iteration.
*/
#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \
for ((wb_cur) = __wb_iter_init(iter, bdi, start_blkcg_id); \
(wb_cur); (wb_cur) = __wb_iter_next(iter, bdi))
#else /* CONFIG_CGROUP_WRITEBACK */
static inline bool inode_cgwb_enabled(struct inode *inode)
@ -445,6 +500,14 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)
{
}
struct wb_iter {
int next_id;
};
#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \
for ((iter)->next_id = (start_blkcg_id); \
({ (wb_cur) = !(iter)->next_id++ ? &(bdi)->wb : NULL; }); )
static inline int inode_congested(struct inode *inode, int cong_bits)
{
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);