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: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan 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: Jens Axboe <axboe@fb.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 5ef05b5c4cff..8c5e2fa68835 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -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;