Re: [PATCH] f2fs: provide f2fs_balance_fs to __write_data_page for dentry pages

[Yunlong Song <yunlong.song@xxxxxxxxxx>]

Hi Jay,
    The SBI_BLOCK_OPS can not cover all the case, once SBI_BLOCK_OPS is 
set, all the normal writeback
(before the SBI_BLOCK_OPS is clear) of dentry pages which do not come 
from write_checkpoint flow will
totally miss all the f2fs_balance_fs check.

On 2017/8/1 8:44, Jaegeuk Kim wrote:
> 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 <yuchao0@xxxxxxxxxx>
> > Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> > ---
> >   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
> .

--
Thanks,
Yunlong Song