Hi Yunlong,

On 07/29, Yunlong Song wrote:
> f2fs_balance_fs of dentry pages is skipped in __write_data_page due to 
> deadlock
> of gc_mutex in write_checkpoint flow. This patch enables f2fs_balance_fs for
> normal dentry page writeback to ensure there are always enough free segments.

So, how about adding SBI_BLOCK_OPS 

/* For s_flag in struct f2fs_sb_info */
enum {
        SBI_IS_DIRTY,                           /* dirty flag for checkpoint */
        SBI_IS_CLOSE,                           /* specify unmounting */
        SBI_NEED_FSCK,                          /* need fsck.f2fs to fix */
        SBI_POR_DOING,                          /* recovery is doing or not */
        SBI_NEED_SB_WRITE,                      /* need to recover superblock */
        SBI_NEED_CP,                            /* need to checkpoint */
===
        SBI_BLOCK_OPS,                          /* doing block_operations */
===
};

How aboud avoiding f2fs_balance_fs() in __write_data_page() by:

        if (!is_sbi_flag_set(sbi, SBI_BLOCK_OPS) || !S_ISDIR(inode->i_mode))
                f2fs_balance_fs();

In block_operations(),
        set_sbi_flag(sbi, SBI_BLOCK_OPS);
        ...
        clear_sbi_flag(sbi, SBI_BLOCK_OPS);

Thanks,

> 
> Reported-by: Chao Yu <yuch...@huawei.com>
> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
> ---
>  fs/f2fs/checkpoint.c |  2 +-
>  fs/f2fs/data.c       | 67 
> +++++++++++++++++++++++++++++++++++++++++++++-------
>  fs/f2fs/f2fs.h       |  1 +
>  3 files changed, 61 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 3c84a25..2882878 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -904,7 +904,7 @@ int sync_dirty_inodes(struct f2fs_sb_info *sbi, enum 
> inode_type type)
>       if (inode) {
>               unsigned long cur_ino = inode->i_ino;
>  
> -             filemap_fdatawrite(inode->i_mapping);
> +             f2fs_filemap_fdatawrite(inode->i_mapping, is_dir);
>               iput(inode);
>               /* We need to give cpu to another writers. */
>               if (ino == cur_ino) {
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index aefc2a5..ed7efa5 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1475,7 +1475,7 @@ int do_write_data_page(struct f2fs_io_info *fio)
>  }
>  
>  static int __write_data_page(struct page *page, bool *submitted,
> -                             struct writeback_control *wbc)
> +                             struct writeback_control *wbc, bool do_balance)
>  {
>       struct inode *inode = page->mapping->host;
>       struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> @@ -1578,7 +1578,7 @@ static int __write_data_page(struct page *page, bool 
> *submitted,
>       }
>  
>       unlock_page(page);
> -     if (!S_ISDIR(inode->i_mode))
> +     if (do_balance)
>               f2fs_balance_fs(sbi, need_balance_fs);
>  
>       if (unlikely(f2fs_cp_error(sbi))) {
> @@ -1602,7 +1602,7 @@ static int __write_data_page(struct page *page, bool 
> *submitted,
>  static int f2fs_write_data_page(struct page *page,
>                                       struct writeback_control *wbc)
>  {
> -     return __write_data_page(page, NULL, wbc);
> +     return __write_data_page(page, NULL, wbc, true);
>  }
>  
>  /*
> @@ -1611,7 +1611,7 @@ static int f2fs_write_data_page(struct page *page,
>   * warm/hot data page.
>   */
>  static int f2fs_write_cache_pages(struct address_space *mapping,
> -                                     struct writeback_control *wbc)
> +                                     struct writeback_control *wbc, bool 
> do_balance)
>  {
>       int ret = 0;
>       int done = 0;
> @@ -1701,7 +1701,7 @@ static int f2fs_write_cache_pages(struct address_space 
> *mapping,
>                       if (!clear_page_dirty_for_io(page))
>                               goto continue_unlock;
>  
> -                     ret = __write_data_page(page, &submitted, wbc);
> +                     ret = __write_data_page(page, &submitted, wbc, 
> do_balance);
>                       if (unlikely(ret)) {
>                               /*
>                                * keep nr_to_write, since vfs uses this to
> @@ -1756,8 +1756,8 @@ static int f2fs_write_cache_pages(struct address_space 
> *mapping,
>       return ret;
>  }
>  
> -static int f2fs_write_data_pages(struct address_space *mapping,
> -                         struct writeback_control *wbc)
> +static int _f2fs_write_data_pages(struct address_space *mapping,
> +                         struct writeback_control *wbc, bool do_balance)
>  {
>       struct inode *inode = mapping->host;
>       struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> @@ -1794,7 +1794,7 @@ static int f2fs_write_data_pages(struct address_space 
> *mapping,
>               goto skip_write;
>  
>       blk_start_plug(&plug);
> -     ret = f2fs_write_cache_pages(mapping, wbc);
> +     ret = f2fs_write_cache_pages(mapping, wbc, do_balance);
>       blk_finish_plug(&plug);
>  
>       if (wbc->sync_mode == WB_SYNC_ALL)
> @@ -1813,6 +1813,57 @@ static int f2fs_write_data_pages(struct address_space 
> *mapping,
>       return 0;
>  }
>  
> +static int f2fs_write_data_pages(struct address_space *mapping,
> +                         struct writeback_control *wbc)
> +{
> +     return  _f2fs_write_data_pages(mapping, wbc, true);
> +}
> +
> +/*
> + * This function was copied from do_writepages from mm/page-writeback.c.
> + * The major change is changing writepages to _f2fs_write_data_pages.
> + */
> +static int f2fs_do_writepages(struct address_space *mapping,
> +                             struct writeback_control *wbc, bool is_dir)
> +{
> +     int ret;
> +
> +     if (wbc->nr_to_write <= 0)
> +             return 0;
> +     while (1) {
> +             ret = _f2fs_write_data_pages(mapping, wbc, !is_dir);
> +             if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL))
> +                     break;
> +             cond_resched();
> +             congestion_wait(BLK_RW_ASYNC, HZ/50);
> +     }
> +     return ret;
> +}
> +
> +/*
> + * This function was copied from __filemap_fdatawrite_range from
> + * mm/filemap.c. The major change is changing do_writepages to
> + * f2fs_do_writepages.
> + */
> +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool is_dir)
> +{
> +     int ret;
> +     struct writeback_control wbc = {
> +             .sync_mode = WB_SYNC_ALL,
> +             .nr_to_write = LONG_MAX,
> +             .range_start = 0,
> +             .range_end = LLONG_MAX,
> +     };
> +
> +     if (!mapping_cap_writeback_dirty(mapping))
> +             return 0;
> +
> +     wbc_attach_fdatawrite_inode(&wbc, mapping->host);
> +     ret = f2fs_do_writepages(mapping, &wbc, is_dir);
> +     wbc_detach_inode(&wbc);
> +     return ret;
> +}
> +
>  static void f2fs_write_failed(struct address_space *mapping, loff_t to)
>  {
>       struct inode *inode = mapping->host;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9280283..ea9bebb 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2572,6 +2572,7 @@ void f2fs_invalidate_page(struct page *page, unsigned 
> int offset,
>  int f2fs_migrate_page(struct address_space *mapping, struct page *newpage,
>                       struct page *page, enum migrate_mode mode);
>  #endif
> +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool is_dir);
>  
>  /*
>   * gc.c
> -- 
> 1.8.5.2

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