On Fri 22-05-15 17:13:44, Tejun Heo wrote:
> In several places, bdi_congested() and its wrappers are used to
> determine whether more IOs should be issued. With cgroup writeback
> support, this question can't be answered solely based on the bdi
> (backing_dev_info). It's dependent on whether the filesystem and bdi
> support cgroup writeback and the blkcg the inode is associated with.
>
> This patch implements inode_congested() and its wrappers which take
> @inode and determines the congestion state considering cgroup
> writeback. The new functions replace bdi_*congested() calls in places
> where the query is about specific inode and task.
>
> There are several filesystem users which also fit this criteria but
> they should be updated when each filesystem implements cgroup
> writeback support.
>
> v2: Now that a given inode is associated with only one wb, congestion
> state can be determined independent from the asking task. Drop
> @task. Spotted by Vivek. Also, converted to take @inode instead
> of @mapping and renamed to inode_congested().
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
> fs/fs-writeback.c | 29 +++++++++++++++++++++++++++++
> include/linux/backing-dev.h | 22 ++++++++++++++++++++++
> mm/fadvise.c | 2 +-
> mm/readahead.c | 2 +-
> mm/vmscan.c | 11 +++++------
> 5 files changed, 58 insertions(+), 8 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 99a2440..7ec491b 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -142,6 +142,35 @@ static void __wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
> wb_queue_work(wb, work);
> }
>
> +#ifdef CONFIG_CGROUP_WRITEBACK
> +
> +/**
> + * inode_congested - test whether an inode is congested
> + * @inode: inode to test for congestion
> + * @cong_bits: mask of WB_[a]sync_congested bits to test
> + *
> + * Tests whether @inode is congested. @cong_bits is the mask of congestion
> + * bits to test and the return value is the mask of set bits.
> + *
> + * If cgroup writeback is enabled for @inode, the congestion state is
> + * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
> + * associated with @inode is congested; otherwise, the root wb's congestion
> + * state is used.
> + */
> +int inode_congested(struct inode *inode, int cong_bits)
> +{
> + if (inode) {
Hum, is there any point in supporting NULL inode with inode_congested()?
That would look more like a programming bug than anything... Otherwise the
patch looks good to me so you can add:
Reviewed-by: Jan Kara <jack@xxxxxxxx>
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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