Re: [PATCH 1/2] remove mapping from balance_dirty_pages*()

[Jan Kara <jack@suse.cz>]

On Tue 09-08-16 15:08:26, Josef Bacik wrote:
> The only reason we pass in the mapping is to get the inode in order to see if
> writeback cgroups is enabled, and even then it only checks the bdi and a super
> block flag.  balance_dirty_pages() doesn't even use the mapping.  Since
> balance_dirty_pages*() works on a bdi level, just pass in the bdi and super
> block directly so we can avoid using mapping.  This will allow us to still use
> balance_dirty_pages for dirty metadata pages that are not backed by an
> address_mapping.
>
> Signed-off-by: Josef Bacik <jbacik@fb.com>

The patch looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/btrfs/disk-io.c          |  4 ++--
>  fs/btrfs/file.c             |  3 ++-
>  fs/btrfs/ioctl.c            |  3 ++-
>  fs/btrfs/relocation.c       |  3 ++-
>  fs/buffer.c                 |  3 ++-
>  fs/iomap.c                  |  3 ++-
>  include/linux/backing-dev.h | 23 +++++++++++++++++------
>  include/linux/writeback.h   |  3 ++-
>  mm/filemap.c                |  4 +++-
>  mm/memory.c                 |  9 +++++++--
>  mm/page-writeback.c         | 15 +++++++--------
>  11 files changed, 48 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 17346f7..c1d951a 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -4024,8 +4024,8 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
>  	ret = percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
>  				     BTRFS_DIRTY_METADATA_THRESH);
>  	if (ret > 0) {
> -		balance_dirty_pages_ratelimited(
> -				   root->fs_info->btree_inode->i_mapping);
> +		balance_dirty_pages_ratelimited(&root->fs_info->bdi,
> +						root->fs_info->sb);
>  	}
>  }
>  
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 9404121..f060b08 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1686,7 +1686,8 @@ again:
>  
>  		cond_resched();
>  
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		if (dirty_pages < (root->nodesize >> PAGE_SHIFT) + 1)
>  			btrfs_btree_balance_dirty(root);
>  
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 14ed1e9..a222bad 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1410,7 +1410,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
>  		}
>  
>  		defrag_count += ret;
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		inode_unlock(inode);
>  
>  		if (newer_than) {
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 4598e29..7fc6ea7 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -3202,7 +3202,8 @@ static int relocate_file_extent_cluster(struct inode *inode,
>  		put_page(page);
>  
>  		index++;
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		btrfs_throttle(BTRFS_I(inode)->root);
>  	}
>  	WARN_ON(nr != cluster->nr);
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 9c8eb9b..9bbe30d 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2386,7 +2386,8 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
>  		BUG_ON(err != len);
>  		err = 0;
>  
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  
>  		if (unlikely(fatal_signal_pending(current))) {
>  			err = -EINTR;
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 48141b8..937e266 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -226,7 +226,8 @@ again:
>  		written += copied;
>  		length -= copied;
>  
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  	} while (iov_iter_count(i) && length);
>  
>  	return written ? written : status;
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 491a917..3b76eeb 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -252,8 +252,9 @@ void wb_blkcg_offline(struct blkcg *blkcg);
>  int inode_congested(struct inode *inode, int cong_bits);
>  
>  /**
> - * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
> - * @inode: inode of interest
> + * bdi_cgwb_enabled - test wether cgroup writeback is enabled on a filesystem
> + * @bdi: the bdi we care about
> + * @sb: the super for the bdi
>   *
>   * cgroup writeback requires support from both the bdi and filesystem.
>   * Also, both memcg and iocg have to be on the default hierarchy.  Test
> @@ -262,15 +263,25 @@ int inode_congested(struct inode *inode, int cong_bits);
>   * Note that the test result may change dynamically on the same inode
>   * depending on how memcg and iocg are configured.
>   */
> -static inline bool inode_cgwb_enabled(struct inode *inode)
> +static inline bool bdi_cgwb_enabled(struct backing_dev_info *bdi,
> +				    struct super_block *sb)
>  {
> -	struct backing_dev_info *bdi = inode_to_bdi(inode);
> -
>  	return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
>  		cgroup_subsys_on_dfl(io_cgrp_subsys) &&
>  		bdi_cap_account_dirty(bdi) &&
>  		(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
> -		(inode->i_sb->s_iflags & SB_I_CGROUPWB);
> +		(sb->s_iflags & SB_I_CGROUPWB);
> +}
> +
> +/**
> + * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
> + * @inode: inode of interest
> + *
> + * Does the inode have cgroup writeback support.
> + */
> +static inline bool inode_cgwb_enabled(struct inode *inode)
> +{
> +	return bdi_cgwb_enabled(inode_to_bdi(inode), inode->i_sb);
>  }
>  
>  /**
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index fc1e16c..256ffc3 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -364,7 +364,8 @@ unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
>  
>  void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
>  void page_writeback_init(void);
> -void balance_dirty_pages_ratelimited(struct address_space *mapping);
> +void balance_dirty_pages_ratelimited(struct backing_dev_info *bdi,
> +				     struct super_block *sb);
>  bool wb_over_bg_thresh(struct bdi_writeback *wb);
>  
>  typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 3083ded..abb0e98 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2667,6 +2667,7 @@ ssize_t generic_perform_write(struct file *file,
>  				struct iov_iter *i, loff_t pos)
>  {
>  	struct address_space *mapping = file->f_mapping;
> +	struct inode *inode = mapping->host;
>  	const struct address_space_operations *a_ops = mapping->a_ops;
>  	long status = 0;
>  	ssize_t written = 0;
> @@ -2746,7 +2747,8 @@ again:
>  		pos += copied;
>  		written += copied;
>  
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  	} while (iov_iter_count(i));
>  
>  	return written ? written : status;
> diff --git a/mm/memory.c b/mm/memory.c
> index 83be99d..d43e73b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -64,6 +64,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/userfaultfd_k.h>
>  #include <linux/dax.h>
> +#include <linux/backing-dev.h>
>  
>  #include <asm/io.h>
>  #include <asm/mmu_context.h>
> @@ -2105,11 +2106,13 @@ static inline int wp_page_reuse(struct fault_env *fe, pte_t orig_pte,
>  		put_page(page);
>  
>  		if ((dirtied || page_mkwrite) && mapping) {
> +			struct inode *inode = mapping->host;
>  			/*
>  			 * Some device drivers do not set page.mapping
>  			 * but still dirty their pages
>  			 */
> -			balance_dirty_pages_ratelimited(mapping);
> +			balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +							inode->i_sb);
>  		}
>  
>  		if (!page_mkwrite)
> @@ -3291,11 +3294,13 @@ static int do_shared_fault(struct fault_env *fe, pgoff_t pgoff)
>  	mapping = page_rmapping(fault_page);
>  	unlock_page(fault_page);
>  	if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
> +		struct inode *inode = mapping->host;
>  		/*
>  		 * Some device drivers do not set page.mapping but still
>  		 * dirty their pages
>  		 */
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  	}
>  
>  	if (!vma->vm_ops->page_mkwrite)
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index f4cd7d8..121a6e3 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1559,8 +1559,7 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
>   * If we're over `background_thresh' then the writeback threads are woken to
>   * perform some writeout.
>   */
> -static void balance_dirty_pages(struct address_space *mapping,
> -				struct bdi_writeback *wb,
> +static void balance_dirty_pages(struct bdi_writeback *wb,
>  				unsigned long pages_dirtied)
>  {
>  	struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) };
> @@ -1849,7 +1848,8 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
>  
>  /**
>   * balance_dirty_pages_ratelimited - balance dirty memory state
> - * @mapping: address_space which was dirtied
> + * @bdi: the bdi that was dirtied
> + * @sb: the super block that was dirtied
>   *
>   * Processes which are dirtying memory should call in here once for each page
>   * which was newly dirtied.  The function will periodically check the system's
> @@ -1860,10 +1860,9 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
>   * limit we decrease the ratelimiting by a lot, to prevent individual processes
>   * from overshooting the limit by (ratelimit_pages) each.
>   */
> -void balance_dirty_pages_ratelimited(struct address_space *mapping)
> +void balance_dirty_pages_ratelimited(struct backing_dev_info *bdi,
> +				     struct super_block *sb)
>  {
> -	struct inode *inode = mapping->host;
> -	struct backing_dev_info *bdi = inode_to_bdi(inode);
>  	struct bdi_writeback *wb = NULL;
>  	int ratelimit;
>  	int *p;
> @@ -1871,7 +1870,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
>  	if (!bdi_cap_account_dirty(bdi))
>  		return;
>  
> -	if (inode_cgwb_enabled(inode))
> +	if (bdi_cgwb_enabled(bdi, sb))
>  		wb = wb_get_create_current(bdi, GFP_KERNEL);
>  	if (!wb)
>  		wb = &bdi->wb;
> @@ -1909,7 +1908,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
>  	preempt_enable();
>  
>  	if (unlikely(current->nr_dirtied >= ratelimit))
> -		balance_dirty_pages(mapping, wb, current->nr_dirtied);
> +		balance_dirty_pages(wb, current->nr_dirtied);
>  
>  	wb_put(wb);
>  }
> -- 
> 1.8.3.1
> 
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR