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

Jan Kara
2015-01-14T12:59:22Z

On Wed 14-01-15 10:42:33, Christoph Hellwig wrote:
> 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>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> 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
>
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--
Jan Kara <jack@suse.cz>
SUSE Labs, CR