linux-kernel - [PATCH 29/45] writeback: move i_wb_list emptiness test into inode_wb_list

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Date:	Tue,  6 Jan 2015 16:26:06 -0500
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk
Cc:	linux-kernel@...r.kernel.org, jack@...e.cz, hch@...radead.org,
	hannes@...xchg.org, linux-fsdevel@...r.kernel.org,
	vgoyal@...hat.com, lizefan@...wei.com, cgroups@...r.kernel.org,
	linux-mm@...ck.org, mhocko@...e.cz, clm@...com,
	fengguang.wu@...el.com, david@...morbit.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 29/45] writeback: move i_wb_list emptiness test into inode_wb_list_del() from its caller

inode_wb_list_del() has one caller, evict(), which tests whether
inode->i_wb_list is empty before invoking the function.  With cgroup
writeback support, an inode may belong to multiple bdi_writeback's
rendering this test incorrect or at least insufficient.  This patch
moves the test into inode_wb_list_del() so that later patches can
update the logic in the function proper.

This does add a function call and jump when a clean inode is being
evicted but this shouldn't be anything noticeable and if it ever is
making that part an inline logic in fs/internal.h is easy.

This patch is pure code reorganization.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Jan Kara <jack@...e.cz>
---
 fs/fs-writeback.c | 3 +++
 fs/inode.c        | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4094d30..0fcdfe9 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -510,6 +510,9 @@ void inode_wb_list_del(struct inode *inode)
 	struct backing_dev_info *bdi = inode_to_bdi(inode);
 	struct bdi_writeback *wb = &bdi->wb;
 
+	if (list_empty(&inode->i_wb_list))
+		return;
+
 	spin_lock(&wb->list_lock);
 	inode_wb_list_del_locked(inode, wb);
 	spin_unlock(&wb->list_lock);
diff --git a/fs/inode.c b/fs/inode.c
index aa149e7..7fbfc00 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -536,9 +536,7 @@ static void evict(struct inode *inode)
 	BUG_ON(!(inode->i_state & I_FREEING));
 	BUG_ON(!list_empty(&inode->i_lru));
 
-	if (!list_empty(&inode->i_wb_list))
-		inode_wb_list_del(inode);
-
+	inode_wb_list_del(inode);
 	inode_sb_list_del(inode);
 
 	/*
-- 
2.1.0

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