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.
Yep, let me reuse nm_i::avaiable_nids in v2 patch. :) Thanks, > > 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 > > . >
