[PATCH 04/12] block_dev: only write bdev inode on close

Christoph Hellwig
2015-01-14T09:42:33Z

Since 018a17bdc865 ("bdi: reimplement bdev_inode_switch_bdi()") the
block device code writes out all dirty data whenever switching the
backing_dev_info for a block device inode. But a block device inode can
only be dirtied when it is in use, which means we only have to write it
out on the final blkdev_put, but not when doing a blkdev_get.

Factoring out the write out from the bdi list switch prepares from
removing the list switch later in the series.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
---
fs/block_dev.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b48c41b..026ca7b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -49,6 +49,17 @@ inline struct block_device *I_BDEV(struct inode *inode)
}
EXPORT_SYMBOL(I_BDEV);

+static void bdev_write_inode(struct inode *inode)
+{
+ spin_lock(&inode->i_lock);
+ while (inode->i_state & I_DIRTY) {
+ spin_unlock(&inode->i_lock);
+ WARN_ON_ONCE(write_inode_now(inode, true));
+ spin_lock(&inode->i_lock);
+ }
+ spin_unlock(&inode->i_lock);
+}
+
/*
* Move the inode from its current bdi to a new bdi. Make sure the inode
* is clean before moving so that it doesn't linger on the old bdi.
@@ -56,16 +67,10 @@ EXPORT_SYMBOL(I_BDEV);
static void bdev_inode_switch_bdi(struct inode *inode,
struct backing_dev_info *dst)
{
- while (true) {
- spin_lock(&inode->i_lock);
- if (!(inode->i_state & I_DIRTY)) {
- inode->i_data.backing_dev_info = dst;
- spin_unlock(&inode->i_lock);
- return;
- }
- spin_unlock(&inode->i_lock);
- WARN_ON_ONCE(write_inode_now(inode, true));
- }
+ spin_lock(&inode->i_lock);
+ WARN_ON_ONCE(inode->i_state & I_DIRTY);
+ inode->i_data.backing_dev_info = dst;
+ spin_unlock(&inode->i_lock);
}

/* Kill _all_ buffers and pagecache , dirty or not.. */
@@ -1464,9 +1469,11 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
WARN_ON_ONCE(bdev->bd_holders);
sync_blockdev(bdev);
kill_bdev(bdev);
- /* ->release can cause the old bdi to disappear,
- * so must switch it out first
+ /*
+ * ->release can cause the queue to disappear, so flush all
+ * dirty data before.
*/
+ bdev_write_inode(bdev->bd_inode);
bdev_inode_switch_bdi(bdev->bd_inode,
&default_backing_dev_info);
}
--
1.9.1