Re: [PATCH 11/12] bdi: invert BDI_CAP_NO_ACCT_WB

Jan Kara
2020-09-17T09:27:51Z

On Thu 10-09-20 16:48:31, Christoph Hellwig wrote:
> Replace BDI_CAP_NO_ACCT_WB with a positive BDI_CAP_WRITEBACK_ACCT to
> make the checks more obvious. Also remove the pointless
> bdi_cap_account_writeback wrapper that just obsfucates the check.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

The patch looks good to me. You can add:

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

Honza

> ---
> fs/fuse/inode.c | 3 ++-
> include/linux/backing-dev.h | 13 +++----------
> mm/backing-dev.c | 1 +
> mm/page-writeback.c | 4 ++--
> 4 files changed, 8 insertions(+), 13 deletions(-)
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 17b00670fb539e..581329203d6860 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1050,7 +1050,8 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
> return err;
>
> /* fuse does it's own writeback accounting */
> - sb->s_bdi->capabilities = BDI_CAP_NO_ACCT_WB | BDI_CAP_STRICTLIMIT;
> + sb->s_bdi->capabilities &= ~BDI_CAP_WRITEBACK_ACCT;
> + sb->s_bdi->capabilities |= BDI_CAP_STRICTLIMIT;
>
> /*
> * For a single fuse filesystem use max 1% of dirty +
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 5da4ea3dd0cc5c..b217344a2c63be 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -120,17 +120,17 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
> *
> * BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
> * BDI_CAP_NO_WRITEBACK: Don't write pages back
> - * BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
> + * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages
> * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
> */
> #define BDI_CAP_NO_ACCT_DIRTY 0x00000001
> #define BDI_CAP_NO_WRITEBACK 0x00000002
> -#define BDI_CAP_NO_ACCT_WB 0x00000004
> +#define BDI_CAP_WRITEBACK_ACCT 0x00000004
> #define BDI_CAP_STRICTLIMIT 0x00000010
> #define BDI_CAP_CGROUP_WRITEBACK 0x00000020
>
> #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
> - (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
> + (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY)
>
> extern struct backing_dev_info noop_backing_dev_info;
>
> @@ -179,13 +179,6 @@ static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
> return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
> }
>
> -static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
> -{
> - /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
> - return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
> - BDI_CAP_NO_WRITEBACK));
> -}
> -
> static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
> {
> return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index f9a2842bd81c3d..ab0415dde5c66c 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -744,6 +744,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
> kfree(bdi);
> return NULL;
> }
> + bdi->capabilities = BDI_CAP_WRITEBACK_ACCT;
> bdi->ra_pages = VM_READAHEAD_PAGES;
> bdi->io_pages = VM_READAHEAD_PAGES;
> return bdi;
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index e9c36521461aaa..0139f9622a92da 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2738,7 +2738,7 @@ int test_clear_page_writeback(struct page *page)
> if (ret) {
> __xa_clear_mark(&mapping->i_pages, page_index(page),
> PAGECACHE_TAG_WRITEBACK);
> - if (bdi_cap_account_writeback(bdi)) {
> + if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
> struct bdi_writeback *wb = inode_to_wb(inode);
>
> dec_wb_stat(wb, WB_WRITEBACK);
> @@ -2791,7 +2791,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
> PAGECACHE_TAG_WRITEBACK);
>
> xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
> - if (bdi_cap_account_writeback(bdi))
> + if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT)
> inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
>
> /*
> --
> 2.28.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR