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Commit 93f78d88 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: move backing_dev_info->bdi_stat[] into bdi_writeback 



Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear.  For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi.  To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->bdi_stat[] into wb.

* enum bdi_stat_item is renamed to wb_stat_item and the prefix of all
  enums is changed from BDI_ to WB_.

* BDI_STAT_BATCH() -> WB_STAT_BATCH()

* [__]{add|inc|dec|sum}_wb_stat(bdi, ...) -> [__]{add|inc}_wb_stat(wb, ...)

* bdi_stat[_error]() -> wb_stat[_error]()

* bdi_writeout_inc() -> wb_writeout_inc()

* stat init is moved to bdi_wb_init() and bdi_wb_exit() is added and
  frees stat.

* As there's still only one bdi_writeback per backing_dev_info, all
  uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
  introducing no behavior changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 4452226e

fs/fs-writeback.c

+1 −1
Original line number Diff line number Diff line
@@ -840,7 +840,7 @@ static bool over_bground_thresh(struct backing_dev_info *bdi) 
	    global_page_state(NR_UNSTABLE_NFS) > background_thresh)

		return true;



	if (bdi_stat(bdi, BDI_RECLAIMABLE) >

	if (wb_stat(&bdi->wb, WB_RECLAIMABLE) >

				bdi_dirty_limit(bdi, background_thresh))

		return true;

fs/fuse/file.c

+6 −6
Original line number Diff line number Diff line
@@ -1445,9 +1445,9 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req) 


	list_del(&req->writepages_entry);

	for (i = 0; i < req->num_pages; i++) {

		dec_bdi_stat(bdi, BDI_WRITEBACK);

		dec_wb_stat(&bdi->wb, WB_WRITEBACK);

		dec_zone_page_state(req->pages[i], NR_WRITEBACK_TEMP);

		bdi_writeout_inc(bdi);

		wb_writeout_inc(&bdi->wb);

	}

	wake_up(&fi->page_waitq);

}
@@ -1634,7 +1634,7 @@ static int fuse_writepage_locked(struct page *page) 
	req->end = fuse_writepage_end;

	req->inode = inode;



	inc_bdi_stat(inode_to_bdi(inode), BDI_WRITEBACK);

	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);

	inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);



	spin_lock(&fc->lock);
@@ -1749,9 +1749,9 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req, 
		copy_highpage(old_req->pages[0], page);

		spin_unlock(&fc->lock);



		dec_bdi_stat(bdi, BDI_WRITEBACK);

		dec_wb_stat(&bdi->wb, WB_WRITEBACK);

		dec_zone_page_state(page, NR_WRITEBACK_TEMP);

		bdi_writeout_inc(bdi);

		wb_writeout_inc(&bdi->wb);

		fuse_writepage_free(fc, new_req);

		fuse_request_free(new_req);

		goto out;
@@ -1848,7 +1848,7 @@ static int fuse_writepages_fill(struct page *page, 
	req->page_descs[req->num_pages].offset = 0;

	req->page_descs[req->num_pages].length = PAGE_SIZE;



	inc_bdi_stat(inode_to_bdi(inode), BDI_WRITEBACK);

	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);

	inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);



	err = 0;

fs/nfs/internal.h

+1 −1
Original line number Diff line number Diff line
@@ -607,7 +607,7 @@ void nfs_mark_page_unstable(struct page *page) 
	struct inode *inode = page_file_mapping(page)->host;



	inc_zone_page_state(page, NR_UNSTABLE_NFS);

	inc_bdi_stat(inode_to_bdi(inode), BDI_RECLAIMABLE);

	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_RECLAIMABLE);

	 __mark_inode_dirty(inode, I_DIRTY_DATASYNC);

}

fs/nfs/write.c

+2 −1
Original line number Diff line number Diff line
@@ -853,7 +853,8 @@ static void 
nfs_clear_page_commit(struct page *page)

{

	dec_zone_page_state(page, NR_UNSTABLE_NFS);

	dec_bdi_stat(inode_to_bdi(page_file_mapping(page)->host), BDI_RECLAIMABLE);

	dec_wb_stat(&inode_to_bdi(page_file_mapping(page)->host)->wb,

		    WB_RECLAIMABLE);

}



/* Called holding inode (/cinfo) lock */

include/linux/backing-dev.h

+32 −36
Original line number Diff line number Diff line
@@ -36,15 +36,15 @@ enum wb_state { 


typedef int (congested_fn)(void *, int);



enum bdi_stat_item {

	BDI_RECLAIMABLE,

	BDI_WRITEBACK,

	BDI_DIRTIED,

	BDI_WRITTEN,

	NR_BDI_STAT_ITEMS

enum wb_stat_item {

	WB_RECLAIMABLE,

	WB_WRITEBACK,

	WB_DIRTIED,

	WB_WRITTEN,

	NR_WB_STAT_ITEMS

};



#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))

#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))



struct bdi_writeback {

	struct backing_dev_info *bdi;	/* our parent bdi */
@@ -58,6 +58,8 @@ struct bdi_writeback { 
	struct list_head b_more_io;	/* parked for more writeback */

	struct list_head b_dirty_time;	/* time stamps are dirty */

	spinlock_t list_lock;		/* protects the b_* lists */



	struct percpu_counter stat[NR_WB_STAT_ITEMS];

};



struct backing_dev_info {
@@ -69,8 +71,6 @@ struct backing_dev_info { 


	char *name;



	struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];



	unsigned long bw_time_stamp;	/* last time write bw is updated */

	unsigned long dirtied_stamp;

	unsigned long written_stamp;	/* pages written at bw_time_stamp */
@@ -137,78 +137,74 @@ static inline int wb_has_dirty_io(struct bdi_writeback *wb) 
	       !list_empty(&wb->b_more_io);

}



static inline void __add_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item, s64 amount)

static inline void __add_wb_stat(struct bdi_writeback *wb,

				 enum wb_stat_item item, s64 amount)

{

	__percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);

	__percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);

}



static inline void __inc_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline void __inc_wb_stat(struct bdi_writeback *wb,

				 enum wb_stat_item item)

{

	__add_bdi_stat(bdi, item, 1);

	__add_wb_stat(wb, item, 1);

}



static inline void inc_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)

{

	unsigned long flags;



	local_irq_save(flags);

	__inc_bdi_stat(bdi, item);

	__inc_wb_stat(wb, item);

	local_irq_restore(flags);

}



static inline void __dec_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline void __dec_wb_stat(struct bdi_writeback *wb,

				 enum wb_stat_item item)

{

	__add_bdi_stat(bdi, item, -1);

	__add_wb_stat(wb, item, -1);

}



static inline void dec_bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)

{

	unsigned long flags;



	local_irq_save(flags);

	__dec_bdi_stat(bdi, item);

	__dec_wb_stat(wb, item);

	local_irq_restore(flags);

}



static inline s64 bdi_stat(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)

{

	return percpu_counter_read_positive(&bdi->bdi_stat[item]);

	return percpu_counter_read_positive(&wb->stat[item]);

}



static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline s64 __wb_stat_sum(struct bdi_writeback *wb,

				enum wb_stat_item item)

{

	return percpu_counter_sum_positive(&bdi->bdi_stat[item]);

	return percpu_counter_sum_positive(&wb->stat[item]);

}



static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,

		enum bdi_stat_item item)

static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)

{

	s64 sum;

	unsigned long flags;



	local_irq_save(flags);

	sum = __bdi_stat_sum(bdi, item);

	sum = __wb_stat_sum(wb, item);

	local_irq_restore(flags);



	return sum;

}



extern void bdi_writeout_inc(struct backing_dev_info *bdi);

extern void wb_writeout_inc(struct bdi_writeback *wb);



/*

 * maximal error of a stat counter.

 */

static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)

static inline unsigned long wb_stat_error(struct bdi_writeback *wb)

{

#ifdef CONFIG_SMP

	return nr_cpu_ids * BDI_STAT_BATCH;

	return nr_cpu_ids * WB_STAT_BATCH;

#else

	return 1;

#endif