[PATCH 11/12] bdi: invert BDI_CAP_NO_ACCT_WB

[Christoph Hellwig]

Replace BDI_CAP_NO_ACCT_WB with a positive BDI_CAP_WRITEBACK_ACCT to
make the checks more obvious.  Also remove the pointless
bdi_cap_account_writeback wrapper that just obsfucates the check.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn at wdc.com>
---
 fs/fuse/inode.c             |  3 ++-
 include/linux/backing-dev.h | 13 +++----------
 mm/backing-dev.c            |  1 +
 mm/page-writeback.c         |  4 ++--
 4 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 17b00670fb539e..581329203d6860 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1050,7 +1050,8 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
 		return err;
 
 	/* fuse does it's own writeback accounting */
-	sb->s_bdi->capabilities = BDI_CAP_NO_ACCT_WB | BDI_CAP_STRICTLIMIT;
+	sb->s_bdi->capabilities &= ~BDI_CAP_WRITEBACK_ACCT;
+	sb->s_bdi->capabilities |= BDI_CAP_STRICTLIMIT;
 
 	/*
 	 * For a single fuse filesystem use max 1% of dirty +
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 5da4ea3dd0cc5c..b217344a2c63be 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -120,17 +120,17 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
  *
  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
- * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
+ * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages
  * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.
  */
 #define BDI_CAP_NO_ACCT_DIRTY	0x00000001
 #define BDI_CAP_NO_WRITEBACK	0x00000002
-#define BDI_CAP_NO_ACCT_WB	0x00000004
+#define BDI_CAP_WRITEBACK_ACCT	0x00000004
 #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)
+	(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY)
 
 extern struct backing_dev_info noop_backing_dev_info;
 
@@ -179,13 +179,6 @@ static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 	return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 }
 
-static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
-{
-	/* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
-	return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
-				      BDI_CAP_NO_WRITEBACK));
-}
-
 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 {
 	return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index f9a2842bd81c3d..ab0415dde5c66c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -744,6 +744,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
 		kfree(bdi);
 		return NULL;
 	}
+	bdi->capabilities = BDI_CAP_WRITEBACK_ACCT;
 	bdi->ra_pages = VM_READAHEAD_PAGES;
 	bdi->io_pages = VM_READAHEAD_PAGES;
 	return bdi;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e9c36521461aaa..0139f9622a92da 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2738,7 +2738,7 @@ int test_clear_page_writeback(struct page *page)
 		if (ret) {
 			__xa_clear_mark(&mapping->i_pages, page_index(page),
 						PAGECACHE_TAG_WRITEBACK);
-			if (bdi_cap_account_writeback(bdi)) {
+			if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
 				struct bdi_writeback *wb = inode_to_wb(inode);
 
 				dec_wb_stat(wb, WB_WRITEBACK);
@@ -2791,7 +2791,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 						   PAGECACHE_TAG_WRITEBACK);
 
 			xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
-			if (bdi_cap_account_writeback(bdi))
+			if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT)
 				inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
 
 			/*
-- 
2.28.0