Re: [f2fs-dev] [PATCH] f2fs: fix to account total free nid correctly

[heyunlei]

On 2016/11/15 4:45, Jaegeuk Kim wrote:
> On Mon, Nov 14, 2016 at 07:24:56PM +0800, Chao Yu wrote:
> > Thread A		Thread B		Thread C
> > - f2fs_create
> >  - f2fs_new_inode
> >   - f2fs_lock_op
> >    - alloc_nid
> >     alloc last nid
> >   - f2fs_unlock_op
> > 			- f2fs_create
> > 			 - f2fs_new_inode
> > 			  - f2fs_lock_op
> > 			   - alloc_nid
> > 			    as node count still not
> > 			    be increased, we will
> > 			    loop in alloc_nid
> > 						- f2fs_write_node_pages
> > 						 - f2fs_balance_fs_bg
> > 						  - f2fs_sync_fs
> > 						   - write_checkpoint
> > 						    - block_operations
> > 						     - f2fs_lock_all
> >  - f2fs_lock_op
> >
> > While creating new inode, we do not allocate and account nid atomically,
> > so that when there is almost no free nids left, we may encounter deadloop
> > like above stack.
> >
> > In order to avoid that, add nm_i::free_nid_cnt for accounting free nids
> > and do nid allocation atomically during node creation.
>
> How about using nm_i::avaiable_nids for this?
> It seems that we don't need both of variables at the same time.
>
> Thanks,
>
> > Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> > ---
> >  fs/f2fs/f2fs.h |  1 +
> >  fs/f2fs/node.c | 19 +++++++++++++++----
> >  2 files changed, 16 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 6de1fbf..9de6f20 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -551,6 +551,7 @@ struct f2fs_nm_info {
> >  	struct radix_tree_root free_nid_root;/* root of the free_nid cache */
> >  	struct list_head nid_list[MAX_NID_LIST];/* lists for free nids */
> >  	unsigned int nid_cnt[MAX_NID_LIST];	/* the number of free node id */
> > +	unsigned int free_nid_cnt;	/* the number of total free nid */
> >  	spinlock_t nid_list_lock;	/* protect nid lists ops */
> >  	struct mutex build_lock;	/* lock for build free nids */
> >
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index d58438f..e412d0e 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -1885,11 +1885,13 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
> >  		return false;
> >  	}
> >  #endif
> > -	if (unlikely(sbi->total_valid_node_count + 1 > nm_i->available_nids))
> > -		return false;
> > -
> >  	spin_lock(&nm_i->nid_list_lock);
> >
> > +	if (unlikely(nm_i->free_nid_cnt == 0)) {
> > +		spin_unlock(&nm_i->nid_list_lock);
> > +		return false;
> > +	}
> > +
> >  	/* We should not use stale free nids created by build_free_nids */
> >  	if (nm_i->nid_cnt[FREE_NID_LIST] && !on_build_free_nids(nm_i)) {
> >  		f2fs_bug_on(sbi, list_empty(&nm_i->nid_list[FREE_NID_LIST]));
> > @@ -1900,6 +1902,7 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
> >  		__remove_nid_from_list(sbi, i, FREE_NID_LIST, true);
> >  		i->state = NID_ALLOC;
> >  		__insert_nid_to_list(sbi, i, ALLOC_NID_LIST, false);
> > +		nm_i->free_nid_cnt--;
> >  		spin_unlock(&nm_i->nid_list_lock);
> >  		return true;
> >  	}
> > @@ -1951,6 +1954,9 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid)
> >  		i->state = NID_NEW;
> >  		__insert_nid_to_list(sbi, i, FREE_NID_LIST, false);
> >  	}
> > +
> > +	nm_i->free_nid_cnt++;
> > +
> >  	spin_unlock(&nm_i->nid_list_lock);
> >
> >  	if (need_free)
> > @@ -2222,8 +2228,12 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
> >  		raw_nat_from_node_info(raw_ne, &ne->ni);
> >  		nat_reset_flag(ne);
> >  		__clear_nat_cache_dirty(NM_I(sbi), ne);
> > -		if (nat_get_blkaddr(ne) == NULL_ADDR)
> > +		if (nat_get_blkaddr(ne) == NULL_ADDR) {
> >  			add_free_nid(sbi, nid, false);
> > +			spin_lock(&NM_I(sbi)->nid_list_lock);
> > +			NM_I(sbi)->free_nid_cnt++;
Hi all,
	Here, we should consider clean NULL_ADDR nat entry in journal.

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index dcfab29..b22ecb0 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -158,6 +158,13 @@ static void __set_nat_cache_dirty(struct f2fs_nm_info *nm_i,
        if (get_nat_flag(ne, IS_DIRTY))
                return;

+       if (ne->ni.blk_addr == NULL_ADDR) {
+               spin_lock(&nm_i->free_nid_list_lock);
+               nm_i->available_nids--;
+               spin_unlock(&nm_i->free_nid_list_lock);
+       }
+
+

Thanks.

> > +			spin_unlock(&NM_I(sbi)->nid_list_lock);
> > +		}
> >  	}
> >
> >  	if (to_journal)
> > @@ -2302,6 +2312,7 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
> >  	nm_i->nid_cnt[FREE_NID_LIST] = 0;
> >  	nm_i->nid_cnt[ALLOC_NID_LIST] = 0;
> >  	nm_i->nat_cnt = 0;
> > +	nm_i->free_nid_cnt = nm_i->available_nids - sbi->total_valid_node_count;
> >  	nm_i->ram_thresh = DEF_RAM_THRESHOLD;
> >  	nm_i->ra_nid_pages = DEF_RA_NID_PAGES;
> >  	nm_i->dirty_nats_ratio = DEF_DIRTY_NAT_RATIO_THRESHOLD;
> > --
> > 2.8.2.311.gee88674
>
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