Re: [PATCH v3] f2fs: fix out-of-free problem caused by atomic write

[Jaegeuk Kim]

On 11/07, Chao Yu wrote:
> On 2017/11/7 9:55, Jaegeuk Kim wrote:
> > On 11/06, Yunlong Song wrote:
> >> f2fs_balance_fs only actives once in the commit_inmem_pages, but there
> >> are more than one page to commit, so all the other pages will miss the
> >> check. This will lead to out-of-free problem when commit a very large
> >> file. However, we cannot do f2fs_balance_fs for each inmem page, since
> >> this will break atomicity. As a result, we should collect prefree
> >> segments if needed.
> >>
> >> Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> >> ---
> >>  fs/f2fs/f2fs.h    |  1 +
> >>  fs/f2fs/segment.c | 24 +++++++++++++++++++++++-
> >>  2 files changed, 24 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >> index 13a96b8..04ce48f 100644
> >> --- a/fs/f2fs/f2fs.h
> >> +++ b/fs/f2fs/f2fs.h
> >> @@ -610,6 +610,7 @@ struct f2fs_inode_info {
> >>  	struct list_head inmem_pages;	/* inmemory pages managed by f2fs */
> >>  	struct task_struct *inmem_task;	/* store inmemory task */
> >>  	struct mutex inmem_lock;	/* lock for inmemory pages */
> >> +	unsigned long inmem_blocks;	/* inmemory blocks */
> >>  	struct extent_tree *extent_tree;	/* cached extent_tree entry */
> >>  	struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
> >>  	struct rw_semaphore i_mmap_sem;
> >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> >> index 46dfbca..b87ede4 100644
> >> --- a/fs/f2fs/segment.c
> >> +++ b/fs/f2fs/segment.c
> >> @@ -210,6 +210,7 @@ void register_inmem_page(struct inode *inode, struct page *page)
> >>  		list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> >>  	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> >>  	inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
> >> +	fi->inmem_blocks++;
> >>  	mutex_unlock(&fi->inmem_lock);
> >>  
> >>  	trace_f2fs_register_inmem_page(page, INMEM);
> >> @@ -221,6 +222,7 @@ static int __revoke_inmem_pages(struct inode *inode,
> >>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>  	struct inmem_pages *cur, *tmp;
> >>  	int err = 0;
> >> +	struct f2fs_inode_info *fi = F2FS_I(inode);
> >>  
> >>  	list_for_each_entry_safe(cur, tmp, head, list) {
> >>  		struct page *page = cur->page;
> >> @@ -263,6 +265,7 @@ static int __revoke_inmem_pages(struct inode *inode,
> >>  		list_del(&cur->list);
> >>  		kmem_cache_free(inmem_entry_slab, cur);
> >>  		dec_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
> >> +		fi->inmem_blocks--;
> >>  	}
> >>  	return err;
> >>  }
> >> @@ -302,6 +305,10 @@ void drop_inmem_pages(struct inode *inode)
> >>  	if (!list_empty(&fi->inmem_ilist))
> >>  		list_del_init(&fi->inmem_ilist);
> >>  	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> >> +	if (fi->inmem_blocks) {
> >> +		f2fs_bug_on(sbi, 1);
> >> +		fi->inmem_blocks = 0;
> >> +	}
> >>  	mutex_unlock(&fi->inmem_lock);
> >>  
> >>  	clear_inode_flag(inode, FI_ATOMIC_FILE);
> >> @@ -326,6 +333,7 @@ void drop_inmem_page(struct inode *inode, struct page *page)
> >>  
> >>  	f2fs_bug_on(sbi, !cur || cur->page != page);
> >>  	list_del(&cur->list);
> >> +	fi->inmem_blocks--;
> >>  	mutex_unlock(&fi->inmem_lock);
> >>  
> >>  	dec_page_count(sbi, F2FS_INMEM_PAGES);
> >> @@ -410,6 +418,16 @@ int commit_inmem_pages(struct inode *inode)
> >>  
> >>  	INIT_LIST_HEAD(&revoke_list);
> >>  	f2fs_balance_fs(sbi, true);
> >> +	if (prefree_segments(sbi)
> >> +		&& has_not_enough_free_secs(sbi, 0,
> >> +		fi->inmem_blocks / BLKS_PER_SEC(sbi))) {
> >> +		struct cp_control cpc;
> >> +
> >> +		cpc.reason = __get_cp_reason(sbi);
> >> +		err = write_checkpoint(sbi, &cpc);
> >> +		if (err)
> >> +			goto drop;
> > 
> > What do you want to guarantee with this? How about passing target # of segments
> > into f2fs_balance_fs() so that f2fs_gc() could secure wanted free space in a
> > loop?
> 
> Agreed, Jaegeuk, IMO, later we can add one more dirty type F2FS_DIRTY_BUDGET in
> enum count_type, and introduce below function, add them around dirtying
> node/dent/imeta datas.
> 
> void f2fs_budget_space(struct f2fs_sb_info *sbi, unsigned int dirty_budget)
> {
> 	if (dirty_budget)
> 		atomic_add(&sbi->nr_pages[F2FS_DIRTY_BUDGET], dirty_budget);
> 
> 	f2fs_balance_fs(sbi, dirty_budget);
> }
> 
> void f2fs_release_budget(struct f2fs_sb_info *sbi, unsigned int dirty_budget)
> {
> 	atomic_dec(&sbi->nr_pages[F2FS_DIRTY_BUDGET], dirty_budget);
> }
> 
> So that in has_not_enough_free_secs we can calculate all dirty datas include
> F2FS_DIRTY_BUDGET type datas more precisely.
> 
> How about that?

That'd be actually same as what has_not_enough_free_space() does? Missing part
would be inmem_pages case which needs quite larger space.

> 
> Thanks,
> 
> > 
> > Thanks,
> > 
> >> +	}
> >>  	f2fs_lock_op(sbi);
> >>  
> >>  	set_inode_flag(inode, FI_ATOMIC_COMMIT);
> >> @@ -429,7 +447,7 @@ int commit_inmem_pages(struct inode *inode)
> >>  		ret = __revoke_inmem_pages(inode, &revoke_list, false, true);
> >>  		if (ret)
> >>  			err = ret;
> >> -
> >> +drop:
> >>  		/* drop all uncommitted pages */
> >>  		__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
> >>  	}
> >> @@ -437,6 +455,10 @@ int commit_inmem_pages(struct inode *inode)
> >>  	if (!list_empty(&fi->inmem_ilist))
> >>  		list_del_init(&fi->inmem_ilist);
> >>  	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> >> +	if (fi->inmem_blocks) {
> >> +		f2fs_bug_on(sbi, 1);
> >> +		fi->inmem_blocks = 0;
> >> +	}
> >>  	mutex_unlock(&fi->inmem_lock);
> >>  
> >>  	clear_inode_flag(inode, FI_ATOMIC_COMMIT);
> >> -- 
> >> 1.8.5.2
> > 
> > .
> >