Re: [PATCH 01/10] remove mapping from balance_dirty_pages*()

[Liu Bo <bo.li.liu@oracle.com>]

On Tue, Nov 14, 2017 at 04:56:47PM -0500, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> 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.
>

One question below.

> Signed-off-by: Josef Bacik <jbacik@fb.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  drivers/mtd/devices/block2mtd.c | 12 ++++++++----
>  fs/btrfs/disk-io.c              |  3 ++-
>  fs/btrfs/file.c                 |  3 ++-
>  fs/btrfs/ioctl.c                |  3 ++-
>  fs/btrfs/relocation.c           |  3 ++-
>  fs/buffer.c                     |  3 ++-
>  fs/iomap.c                      |  6 ++++--
>  fs/ntfs/attrib.c                | 11 ++++++++---
>  fs/ntfs/file.c                  |  4 ++--
>  include/linux/backing-dev.h     | 29 +++++++++++++++++++++++------
>  include/linux/writeback.h       |  4 +++-
>  mm/filemap.c                    |  4 +++-
>  mm/memory.c                     |  5 ++++-
>  mm/page-writeback.c             | 15 +++++++--------
>  14 files changed, 72 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
> index 7c887f111a7d..7892d0b9fcb0 100644
> --- a/drivers/mtd/devices/block2mtd.c
> +++ b/drivers/mtd/devices/block2mtd.c
> @@ -52,7 +52,8 @@ static struct page *page_read(struct address_space *mapping, int index)
>  /* erase a specified part of the device */
>  static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
>  {
> -	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
> +	struct inode *inode = dev->blkdev->bd_inode;
> +	struct address_space *mapping = inode->i_mapping;
>  	struct page *page;
>  	int index = to >> PAGE_SHIFT;	// page index
>  	int pages = len >> PAGE_SHIFT;
> @@ -71,7 +72,8 @@ static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
>  				memset(page_address(page), 0xff, PAGE_SIZE);
>  				set_page_dirty(page);
>  				unlock_page(page);
> -				balance_dirty_pages_ratelimited(mapping);
> +				balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +								inode->i_sb);
>  				break;
>  			}
>  
> @@ -141,7 +143,8 @@ static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
>  		loff_t to, size_t len, size_t *retlen)
>  {
>  	struct page *page;
> -	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
> +	struct inode *inode = dev->blkdev->bd_inode;
> +	struct address_space *mapping = inode->i_mapping;
>  	int index = to >> PAGE_SHIFT;	// page index
>  	int offset = to & ~PAGE_MASK;	// page offset
>  	int cpylen;
> @@ -162,7 +165,8 @@ static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
>  			memcpy(page_address(page) + offset, buf, cpylen);
>  			set_page_dirty(page);
>  			unlock_page(page);
> -			balance_dirty_pages_ratelimited(mapping);
> +			balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +							inode->i_sb);
>  		}
>  		put_page(page);
>  
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 689b9913ccb5..8b6df7688d52 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -4150,7 +4150,8 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
>  	ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
>  				     BTRFS_DIRTY_METADATA_THRESH);
>  	if (ret > 0) {
> -		balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping);
> +		balance_dirty_pages_ratelimited(fs_info->sb->s_bdi,
> +						fs_info->sb);
>  	}
>  }
>  
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index ab1c38f2dd8c..4bc6cd6509be 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1779,7 +1779,8 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
>  
>  		cond_resched();
>  
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		if (dirty_pages < (fs_info->nodesize >> PAGE_SHIFT) + 1)
>  			btrfs_btree_balance_dirty(fs_info);
>  
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 6a07d4e12fd2..ec92fb5e2b51 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1368,7 +1368,8 @@ 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 4cf2eb67eba6..9f31c5e6c0e5 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -3278,7 +3278,8 @@ static int relocate_file_extent_cluster(struct inode *inode,
>  
>  		index++;
>  		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		btrfs_throttle(fs_info);
>  	}
>  	WARN_ON(nr != cluster->nr);
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 170df856bdb9..36be326a316c 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2421,7 +2421,8 @@ 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 269b24a01f32..0eb1ec680f87 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -223,7 +223,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>  		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;
> @@ -305,7 +306,8 @@ iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>  		written += status;
>  		length -= status;
>  
> -		balance_dirty_pages_ratelimited(inode->i_mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  	} while (length);
>  
>  	return written;
> diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
> index 44a39a099b54..d85368dd82e7 100644
> --- a/fs/ntfs/attrib.c
> +++ b/fs/ntfs/attrib.c
> @@ -25,6 +25,7 @@
>  #include <linux/slab.h>
>  #include <linux/swap.h>
>  #include <linux/writeback.h>
> +#include <linux/backing-dev.h>
>  
>  #include "attrib.h"
>  #include "debug.h"
> @@ -2493,6 +2494,7 @@ s64 ntfs_attr_extend_allocation(ntfs_inode *ni, s64 new_alloc_size,
>  int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
>  {
>  	ntfs_volume *vol = ni->vol;
> +	struct inode *inode = VFS_I(ni);
>  	struct address_space *mapping;
>  	struct page *page;
>  	u8 *kaddr;
> @@ -2545,7 +2547,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
>  		kunmap_atomic(kaddr);
>  		set_page_dirty(page);
>  		put_page(page);
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		cond_resched();
>  		if (idx == end)
>  			goto done;
> @@ -2586,7 +2589,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
>  		/* Finally unlock and release the page. */
>  		unlock_page(page);
>  		put_page(page);
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		cond_resched();
>  	}
>  	/* If there is a last partial page, need to do it the slow way. */
> @@ -2603,7 +2607,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
>  		kunmap_atomic(kaddr);
>  		set_page_dirty(page);
>  		put_page(page);
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
> +						inode->i_sb);
>  		cond_resched();
>  	}
>  done:
> diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
> index 331910fa8442..77b04be4a157 100644
> --- a/fs/ntfs/file.c
> +++ b/fs/ntfs/file.c
> @@ -276,7 +276,7 @@ static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)
>  		 * number of pages we read and make dirty in the case of sparse
>  		 * files.
>  		 */
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(vi), vi->i_sb);
>  		cond_resched();
>  	} while (++index < end_index);
>  	read_lock_irqsave(&ni->size_lock, flags);
> @@ -1913,7 +1913,7 @@ static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
>  		iov_iter_advance(i, copied);
>  		pos += copied;
>  		written += copied;
> -		balance_dirty_pages_ratelimited(mapping);
> +		balance_dirty_pages_ratelimited(inode_to_bdi(vi), vi->i_sb);
>  		if (fatal_signal_pending(current)) {
>  			status = -EINTR;
>  			break;
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 854e1bdd0b2a..14e266d12620 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -228,8 +228,9 @@ 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
> @@ -238,15 +239,25 @@ 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);
>  }
>  
>  /**
> @@ -389,6 +400,12 @@ static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
>  
>  #else	/* CONFIG_CGROUP_WRITEBACK */
>  
> +static inline bool bdi_cgwb_enabled(struct backing_dev_info *bdi,
> +				    struct super_block *sb)
> +{
> +	return false;
> +}
> +
>  static inline bool inode_cgwb_enabled(struct inode *inode)
>  {
>  	return false;
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index d5815794416c..fa799a4a7755 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -376,7 +376,9 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
>  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 balance_dirty_pages_ratelimited(struct address_space *mapping);
> +void page_writeback_init(void);

I'm not getting why page_writeback_init() is exported here.

Others look good.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo

> +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 870971e20967..5ea4878e9c78 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2971,6 +2971,7 @@ 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;
> @@ -3044,7 +3045,8 @@ ssize_t generic_perform_write(struct file *file,
>  		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 ec4e15494901..86f31b3d54c6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -70,6 +70,7 @@
>  #include <linux/userfaultfd_k.h>
>  #include <linux/dax.h>
>  #include <linux/oom.h>
> +#include <linux/backing-dev.h>
>  
>  #include <asm/io.h>
>  #include <asm/mmu_context.h>
> @@ -2391,11 +2392,13 @@ static void fault_dirty_shared_page(struct vm_area_struct *vma,
>  	unlock_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)
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0b9c5cbe8eba..1a47d4296750 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) };
> @@ -1850,7 +1849,8 @@ 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
> @@ -1861,10 +1861,9 @@ 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;
> @@ -1872,7 +1871,7 @@ 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;
> @@ -1910,7 +1909,7 @@ 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);
>  }
> -- 
> 2.7.5
> 

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