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.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>
---
fs/f2fs/f2fs.h | 2 +-
fs/f2fs/node.c | 82 ++++++++++++++++++++++++++--------------------------------
2 files changed, 37 insertions(+), 47 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 6283c8d..20aab02 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -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 */
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index c8f48d4..aede910 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -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);
@@ -1375,41 +1371,36 @@ 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);
- return false;
- }
- }
- mutex_unlock(&nm_i->build_lock);
+ if (sbi->total_valid_node_count + 1 >= nm_i->max_nid)
+ return false;
- /*
- * 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;
- }
- 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);
- if (i->state == NID_NEW)
- break;
- }
+ /* 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);
+ if (i->state == NID_NEW)
+ break;
+ }
- BUG_ON(i->state != NID_NEW);
- *nid = i->nid;
- i->state = NID_ALLOC;
- nm_i->fcnt--;
+ BUG_ON(i->state != NID_NEW);
+ *nid = i->nid;
+ i->state = NID_ALLOC;
+ nm_i->fcnt--;
+ spin_unlock(&nm_i->free_nid_list_lock);
+ return true;
+ }
spin_unlock(&nm_i->free_nid_list_lock);
- return true;
+
+ /* 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;
}
/*
@@ -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);
--
1.8.1.3.566.gaa39828
--
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