Commit 55008d84 authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

f2fs: enhance alloc_nid and build_free_nids flows 



In order to avoid build_free_nid lock contention, let's change the order of
function calls as follows.

At first, check whether there is enough free nids.
 - If available, just get a free nid with spin_lock without any overhead.
 - Otherwise, conduct build_free_nids.
  : scan nat pages, journal nat entries, and nat cache entries.

We should consider carefullly not to serve free nids intermediately made by
build_free_nids.
We can get stable free nids only after build_free_nids is done.

Reviewed-by: default avatarNamjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent d70b4f53

fs/f2fs/f2fs.h

+1 −1
Original line number Diff line number Diff line
@@ -190,7 +190,6 @@ static inline void set_raw_extent(struct extent_info *ext, 
struct f2fs_nm_info {

	block_t nat_blkaddr;		/* base disk address of NAT */

	nid_t max_nid;			/* maximum possible node ids */

	nid_t init_scan_nid;		/* the first nid to be scanned */

	nid_t next_scan_nid;		/* the next nid to be scanned */



	/* NAT cache management */
@@ -360,6 +359,7 @@ struct f2fs_sb_info { 
	struct mutex writepages;		/* mutex for writepages() */

	unsigned char next_lock_num;		/* round-robin global locks */

	int por_doing;				/* recovery is doing or not */

	int on_build_free_nids;			/* build_free_nids is doing */



	/* for orphan inode management */

	struct list_head orphan_inode_list;	/* orphan inode list */

fs/f2fs/node.c

+36 −46
Original line number Diff line number Diff line
@@ -1309,14 +1309,14 @@ static void build_free_nids(struct f2fs_sb_info *sbi) 
	struct f2fs_nm_info *nm_i = NM_I(sbi);

	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);

	struct f2fs_summary_block *sum = curseg->sum_blk;

	nid_t nid = 0;

	bool is_cycled = false;

	int fcnt = 0;

	int i;

	int fcnt = 0, i = 0;

	nid_t nid = nm_i->next_scan_nid;



	nid = nm_i->next_scan_nid;

	nm_i->init_scan_nid = nid;

	/* Enough entries */

	if (nm_i->fcnt > NAT_ENTRY_PER_BLOCK)

		return;



	/* readahead nat pages to be scanned */

	ra_nat_pages(sbi, nid);



	while (1) {
@@ -1326,19 +1326,15 @@ static void build_free_nids(struct f2fs_sb_info *sbi) 
		f2fs_put_page(page, 1);



		nid += (NAT_ENTRY_PER_BLOCK - (nid % NAT_ENTRY_PER_BLOCK));



		if (nid >= nm_i->max_nid) {

		if (nid >= nm_i->max_nid)

			nid = 0;

			is_cycled = true;

		}

		if (fcnt > MAX_FREE_NIDS)

			break;

		if (is_cycled && nm_i->init_scan_nid <= nid)



		if (i++ == FREE_NID_PAGES)

			break;

	}



	/* go to the next nat page in order to reuse free nids first */

	nm_i->next_scan_nid = nm_i->init_scan_nid + NAT_ENTRY_PER_BLOCK;

	/* go to the next free nat pages to find free nids abundantly */

	nm_i->next_scan_nid = nid;



	/* find free nids from current sum_pages */

	mutex_lock(&curseg->curseg_mutex);
@@ -1375,28 +1371,13 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid) 
	struct free_nid *i = NULL;

	struct list_head *this;

retry:

	mutex_lock(&nm_i->build_lock);

	if (!nm_i->fcnt) {

		/* scan NAT in order to build free nid list */

		build_free_nids(sbi);

		if (!nm_i->fcnt) {

			mutex_unlock(&nm_i->build_lock);

	if (sbi->total_valid_node_count + 1 >= nm_i->max_nid)

		return false;

		}

	}

	mutex_unlock(&nm_i->build_lock);



	/*

	 * We check fcnt again since previous check is racy as

	 * we didn't hold free_nid_list_lock. So other thread

	 * could consume all of free nids.

	 */

	spin_lock(&nm_i->free_nid_list_lock);

	if (!nm_i->fcnt) {

		spin_unlock(&nm_i->free_nid_list_lock);

		goto retry;

	}



	/* We should not use stale free nids created by build_free_nids */

	if (nm_i->fcnt && !sbi->on_build_free_nids) {

		BUG_ON(list_empty(&nm_i->free_nid_list));

		list_for_each(this, &nm_i->free_nid_list) {

			i = list_entry(this, struct free_nid, list);
@@ -1411,6 +1392,16 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid) 
		spin_unlock(&nm_i->free_nid_list_lock);

		return true;

	}

	spin_unlock(&nm_i->free_nid_list_lock);



	/* Let's scan nat pages and its caches to get free nids */

	mutex_lock(&nm_i->build_lock);

	sbi->on_build_free_nids = 1;

	build_free_nids(sbi);

	sbi->on_build_free_nids = 0;

	mutex_unlock(&nm_i->build_lock);

	goto retry;

}



/*

 * alloc_nid() should be called prior to this function.
@@ -1696,7 +1687,6 @@ static int init_node_manager(struct f2fs_sb_info *sbi) 
	spin_lock_init(&nm_i->free_nid_list_lock);

	rwlock_init(&nm_i->nat_tree_lock);



	nm_i->init_scan_nid = le32_to_cpu(sbi->ckpt->next_free_nid);

	nm_i->next_scan_nid = le32_to_cpu(sbi->ckpt->next_free_nid);

	nm_i->bitmap_size = __bitmap_size(sbi, NAT_BITMAP);

	version_bitmap = __bitmap_ptr(sbi, NAT_BITMAP);