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 <[email protected]> > --- > 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++; > + 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
