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From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Song Liu <song@kernel.org>, Hans de Goede <hdegoede@redhat.com>,
        Richard Weinberger <richard@nod.at>,
        Minchan Kim <minchan@kernel.org>,
        linux-mtd@lists.infradead.org, dm-devel@redhat.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        drbd-dev@lists.linbit.com, linux-raid@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        cgroups@vger.kernel.org
Subject: [PATCH 13/14] bdi: invert BDI_CAP_NO_ACCT_WB
Date:   Sun, 26 Jul 2020 17:03:32 +0200
Message-Id: <20200726150333.305527-14-hch@lst.de>
In-Reply-To: <20200726150333.305527-1-hch@lst.de>
References: <20200726150333.305527-1-hch@lst.de>
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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@lst.de>
---
 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 41ec322090fca6..5f5958e1d39060 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;
 	return bdi;
 }
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 27a10536adad30..44c4a588f48df5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2740,7 +2740,7 @@ 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);
@@ -2793,7 +2793,7 @@ 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);
 
 			/*
-- 
2.27.0