Re: [PATCH 12/12] bdi: replace BDI_CAP_NO_{WRITEBACK,ACCT_DIRTY} with a single flag

Jan Kara
2020-09-17T09:32:06Z

On Thu 10-09-20 16:48:32, Christoph Hellwig wrote:
> Replace the two negative flags that are always used together with a
> single positive flag that indicates the writeback capability instead
> of two related non-capabilities. Also remove the pointless wrappers
> to just check the flag.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me. You can add:

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

Honza

> ---
> fs/9p/vfs_file.c | 2 +-
> fs/fs-writeback.c | 7 +++---
> include/linux/backing-dev.h | 48 ++++++++-----------------------------
> mm/backing-dev.c | 6 ++---
> mm/filemap.c | 4 ++--
> mm/memcontrol.c | 2 +-
> mm/memory-failure.c | 2 +-
> mm/migrate.c | 2 +-
> mm/mmap.c | 2 +-
> mm/page-writeback.c | 12 +++++-----
> 10 files changed, 29 insertions(+), 58 deletions(-)
>
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 3576123d82990e..6ecf863bfa2f4b 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -625,7 +625,7 @@ static void v9fs_mmap_vm_close(struct vm_area_struct *vma)
>
> inode = file_inode(vma->vm_file);
>
> - if (!mapping_cap_writeback_dirty(inode->i_mapping))
> + if (!mapping_can_writeback(inode->i_mapping))
> wbc.nr_to_write = 0;
>
> might_sleep();
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 149227160ff0b0..d4f84a2fe0878e 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -2321,7 +2321,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
>
> wb = locked_inode_to_wb_and_lock_list(inode);
>
> - WARN(bdi_cap_writeback_dirty(wb->bdi) &&
> + WARN((wb->bdi->capabilities & BDI_CAP_WRITEBACK) &&
> !test_bit(WB_registered, &wb->state),
> "bdi-%s not registered\n", bdi_dev_name(wb->bdi));
>
> @@ -2346,7 +2346,8 @@ void __mark_inode_dirty(struct inode *inode, int flags)
> * to make sure background write-back happens
> * later.
> */
> - if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
> + if (wakeup_bdi &&
> + (wb->bdi->capabilities & BDI_CAP_WRITEBACK))
> wb_wakeup_delayed(wb);
> return;
> }
> @@ -2581,7 +2582,7 @@ int write_inode_now(struct inode *inode, int sync)
> .range_end = LLONG_MAX,
> };
>
> - if (!mapping_cap_writeback_dirty(inode->i_mapping))
> + if (!mapping_can_writeback(inode->i_mapping))
> wbc.nr_to_write = 0;
>
> might_sleep();
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index b217344a2c63be..44df4fcef65c1e 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -110,27 +110,14 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
> /*
> * Flags in backing_dev_info::capability
> *
> - * The first three flags control whether dirty pages will contribute to the
> - * VM's accounting and whether writepages() should be called for dirty pages
> - * (something that would not, for example, be appropriate for ramfs)
> - *
> - * WARNING: these flags are closely related and should not normally be
> - * used separately. The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
> - * three flags into a single convenience macro.
> - *
> - * BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
> - * BDI_CAP_NO_WRITEBACK: Don't write pages back
> - * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages
> - * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
> + * BDI_CAP_WRITEBACK: Supports dirty page writeback, and dirty pages
> + * should contribute to accounting
> + * 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_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)
> +#define BDI_CAP_WRITEBACK (1 << 0)
> +#define BDI_CAP_WRITEBACK_ACCT (1 << 1)
> +#define BDI_CAP_STRICTLIMIT (1 << 2)
>
> extern struct backing_dev_info noop_backing_dev_info;
>
> @@ -169,24 +156,9 @@ static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
> long congestion_wait(int sync, long timeout);
> long wait_iff_congested(int sync, long timeout);
>
> -static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
> -{
> - return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
> -}
> -
> -static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
> -{
> - return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
> -}
> -
> -static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
> -{
> - return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
> -}
> -
> -static inline bool mapping_cap_account_dirty(struct address_space *mapping)
> +static inline bool mapping_can_writeback(struct address_space *mapping)
> {
> - return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
> + return inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK;
> }
>
> static inline int bdi_sched_wait(void *word)
> @@ -223,7 +195,7 @@ static inline bool inode_cgwb_enabled(struct inode *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_WRITEBACK) &&
> (inode->i_sb->s_iflags & SB_I_CGROUPWB);
> }
>
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index ab0415dde5c66c..5d0991e75ca337 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -14,9 +14,7 @@
> #include <linux/device.h>
> #include <trace/events/writeback.h>
>
> -struct backing_dev_info noop_backing_dev_info = {
> - .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
> -};
> +struct backing_dev_info noop_backing_dev_info;
> EXPORT_SYMBOL_GPL(noop_backing_dev_info);
>
> static struct class *bdi_class;
> @@ -744,7 +742,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
> kfree(bdi);
> return NULL;
> }
> - bdi->capabilities = BDI_CAP_WRITEBACK_ACCT;
> + bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
> bdi->ra_pages = VM_READAHEAD_PAGES;
> bdi->io_pages = VM_READAHEAD_PAGES;
> return bdi;
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 1aaea26556cc7e..6c2a0139e22fa3 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -414,7 +414,7 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
> .range_end = end,
> };
>
> - if (!mapping_cap_writeback_dirty(mapping) ||
> + if (!mapping_can_writeback(mapping) ||
> !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
> return 0;
>
> @@ -1702,7 +1702,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> no_page:
> if (!page && (fgp_flags & FGP_CREAT)) {
> int err;
> - if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
> + if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
> gfp_mask |= __GFP_WRITE;
> if (fgp_flags & FGP_NOFS)
> gfp_mask &= ~__GFP_FS;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b807952b4d431b..d2352f76d6519f 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5643,7 +5643,7 @@ static int mem_cgroup_move_account(struct page *page,
> if (PageDirty(page)) {
> struct address_space *mapping = page_mapping(page);
>
> - if (mapping_cap_account_dirty(mapping)) {
> + if (mapping_can_writeback(mapping)) {
> __mod_lruvec_state(from_vec, NR_FILE_DIRTY,
> -nr_pages);
> __mod_lruvec_state(to_vec, NR_FILE_DIRTY,
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index f1aa6433f40416..a1e73943445e77 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1006,7 +1006,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
> */
> mapping = page_mapping(hpage);
> if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
> - mapping_cap_writeback_dirty(mapping)) {
> + mapping_can_writeback(mapping)) {
> if (page_mkclean(hpage)) {
> SetPageDirty(hpage);
> } else {
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 34a842a8eb6a7b..9d2f42a3a16294 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -503,7 +503,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
> __dec_lruvec_state(old_lruvec, NR_SHMEM);
> __inc_lruvec_state(new_lruvec, NR_SHMEM);
> }
> - if (dirty && mapping_cap_account_dirty(mapping)) {
> + if (dirty && mapping_can_writeback(mapping)) {
> __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
> __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
> __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 40248d84ad5fbd..1fc0e92be4ba9b 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1666,7 +1666,7 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
>
> /* Can the mapping track the dirty pages? */
> return vma->vm_file && vma->vm_file->f_mapping &&
> - mapping_cap_account_dirty(vma->vm_file->f_mapping);
> + mapping_can_writeback(vma->vm_file->f_mapping);
> }
>
> /*
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0139f9622a92da..358d6f28c627b7 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1882,7 +1882,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
> int ratelimit;
> int *p;
>
> - if (!bdi_cap_account_dirty(bdi))
> + if (!(bdi->capabilities & BDI_CAP_WRITEBACK))
> return;
>
> if (inode_cgwb_enabled(inode))
> @@ -2423,7 +2423,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
>
> trace_writeback_dirty_page(page, mapping);
>
> - if (mapping_cap_account_dirty(mapping)) {
> + if (mapping_can_writeback(mapping)) {
> struct bdi_writeback *wb;
>
> inode_attach_wb(inode, page);
> @@ -2450,7 +2450,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
> void account_page_cleaned(struct page *page, struct address_space *mapping,
> struct bdi_writeback *wb)
> {
> - if (mapping_cap_account_dirty(mapping)) {
> + if (mapping_can_writeback(mapping)) {
> dec_lruvec_page_state(page, NR_FILE_DIRTY);
> dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
> dec_wb_stat(wb, WB_RECLAIMABLE);
> @@ -2513,7 +2513,7 @@ void account_page_redirty(struct page *page)
> {
> struct address_space *mapping = page->mapping;
>
> - if (mapping && mapping_cap_account_dirty(mapping)) {
> + if (mapping && mapping_can_writeback(mapping)) {
> struct inode *inode = mapping->host;
> struct bdi_writeback *wb;
> struct wb_lock_cookie cookie = {};
> @@ -2625,7 +2625,7 @@ void __cancel_dirty_page(struct page *page)
> {
> struct address_space *mapping = page_mapping(page);
>
> - if (mapping_cap_account_dirty(mapping)) {
> + if (mapping_can_writeback(mapping)) {
> struct inode *inode = mapping->host;
> struct bdi_writeback *wb;
> struct wb_lock_cookie cookie = {};
> @@ -2665,7 +2665,7 @@ int clear_page_dirty_for_io(struct page *page)
>
> VM_BUG_ON_PAGE(!PageLocked(page), page);
>
> - if (mapping && mapping_cap_account_dirty(mapping)) {
> + if (mapping && mapping_can_writeback(mapping)) {
> struct inode *inode = mapping->host;
> struct bdi_writeback *wb;
> struct wb_lock_cookie cookie = {};
> --
> 2.28.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR