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Message-ID: <20250813040455.3900073-1-wangzijie1@honor.com>
Date: Wed, 13 Aug 2025 12:04:55 +0800
From: wangzijie <wangzijie1@...or.com>
To: <jaegeuk@...nel.org>, <chao@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
<bintian.wang@...or.com>, <feng.han@...or.com>, wangzijie
<wangzijie1@...or.com>
Subject: [f2fs-dev] [PATCH] f2fs: reduce nat_tree_lock hold time when flush nat entries
Sometimes I suffered the nat_tree_lock contention between f2fs_write_checkpoint
and f2fs_get_node_info. Commit a9419b6("f2fs: do not bother checkpoint by
f2fs_get_node_info") also mentioned that situation.
My idea is, when flush nat entries, we can use some structures to record nat
pages we may read, and readahead them before hold nat_tree_lock. Before
impletement code, I did some survey and found a submittion in community.
Subject: f2fs: use bucket sort to avoid tree lookup and list sort when nat flushing
Link: https://lore.kernel.org/linux-f2fs-devel/20170520122435.17574-2-houpengyang@huawei.com/
This patch aims to improve nat entry set sort by using bucket.
I steal that structure and readahead nat pages contain nat entry set which cannot be moved
to journal according to dirty nat entry set bucket.
By doing this, I think there are two benefits to reducing nat_tree_lock hold time when
when flush nat entries.
1. avoid nat set tree lookup and sort
2. readahead nat pages before holding nat_tree_lock
Signed-off-by: wangzijie <wangzijie1@...or.com>
---
fs/f2fs/f2fs.h | 1 +
fs/f2fs/node.c | 70 ++++++++++++++++++++++++--------------------------
fs/f2fs/node.h | 2 +-
3 files changed, 35 insertions(+), 38 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 46be75605..b27cc059f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -975,6 +975,7 @@ struct f2fs_nm_info {
struct radix_tree_root nat_set_root;/* root of the nat set cache */
struct f2fs_rwsem nat_tree_lock; /* protect nat entry tree */
struct list_head nat_entries; /* cached nat entry list (clean) */
+ struct list_head nat_dirty_set[NAT_ENTRY_PER_BLOCK + 1]; /* store dirty nat set */
spinlock_t nat_list_lock; /* protect clean nat entry list */
unsigned int nat_cnt[MAX_NAT_STATE]; /* the # of cached nat entries */
unsigned int nat_blocks; /* # of nat blocks */
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 27743b93e..87c975ee8 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -244,6 +244,12 @@ static void __del_from_nat_cache(struct f2fs_nm_info *nm_i, struct nat_entry *e)
__free_nat_entry(e);
}
+static void __relocate_nat_entry_set(struct f2fs_nm_info *nm_i,
+ struct nat_entry_set *set)
+{
+ list_move_tail(&set->set_list, &nm_i->nat_dirty_set[set->entry_cnt]);
+}
+
static struct nat_entry_set *__grab_nat_entry_set(struct f2fs_nm_info *nm_i,
struct nat_entry *ne)
{
@@ -260,6 +266,7 @@ static struct nat_entry_set *__grab_nat_entry_set(struct f2fs_nm_info *nm_i,
head->set = set;
head->entry_cnt = 0;
f2fs_radix_tree_insert(&nm_i->nat_set_root, set, head);
+ __relocate_nat_entry_set(nm_i, head);
}
return head;
}
@@ -279,8 +286,10 @@ static void __set_nat_cache_dirty(struct f2fs_nm_info *nm_i,
* 2. update old block address to new one;
*/
if (!new_ne && (get_nat_flag(ne, IS_PREALLOC) ||
- !get_nat_flag(ne, IS_DIRTY)))
+ !get_nat_flag(ne, IS_DIRTY))) {
head->entry_cnt++;
+ __relocate_nat_entry_set(nm_i, head);
+ }
set_nat_flag(ne, IS_PREALLOC, new_ne);
@@ -309,6 +318,7 @@ static void __clear_nat_cache_dirty(struct f2fs_nm_info *nm_i,
set_nat_flag(ne, IS_DIRTY, false);
set->entry_cnt--;
+ __relocate_nat_entry_set(nm_i, set);
nm_i->nat_cnt[DIRTY_NAT]--;
nm_i->nat_cnt[RECLAIMABLE_NAT]++;
}
@@ -2976,24 +2986,6 @@ static void remove_nats_in_journal(struct f2fs_sb_info *sbi)
up_write(&curseg->journal_rwsem);
}
-static void __adjust_nat_entry_set(struct nat_entry_set *nes,
- struct list_head *head, int max)
-{
- struct nat_entry_set *cur;
-
- if (nes->entry_cnt >= max)
- goto add_out;
-
- list_for_each_entry(cur, head, set_list) {
- if (cur->entry_cnt >= nes->entry_cnt) {
- list_add(&nes->set_list, cur->set_list.prev);
- return;
- }
- }
-add_out:
- list_add_tail(&nes->set_list, head);
-}
-
static void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
const struct f2fs_nat_block *nat_blk)
{
@@ -3095,6 +3087,7 @@ static int __flush_nat_entry_set(struct f2fs_sb_info *sbi,
/* Allow dirty nats by node block allocation in write_begin */
if (!set->entry_cnt) {
+ list_del(&set->set_list);
radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
kmem_cache_free(nat_entry_set_slab, set);
}
@@ -3109,11 +3102,8 @@ int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
struct f2fs_nm_info *nm_i = NM_I(sbi);
struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
struct f2fs_journal *journal = curseg->journal;
- struct nat_entry_set *setvec[NAT_VEC_SIZE];
struct nat_entry_set *set, *tmp;
- unsigned int found;
- nid_t set_idx = 0;
- LIST_HEAD(sets);
+ int i;
int err = 0;
/*
@@ -3129,6 +3119,16 @@ int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
if (!nm_i->nat_cnt[DIRTY_NAT])
return 0;
+ /* readahead sets which cannot be moved to journal */
+ if (!__has_cursum_space(journal, nm_i->nat_cnt[DIRTY_NAT], NAT_JOURNAL)) {
+ for (i = MAX_NAT_JENTRIES(journal); i <= NAT_ENTRY_PER_BLOCK; i++) {
+ list_for_each_entry_safe(set, tmp, &nm_i->nat_dirty_set[i], set_list) {
+ f2fs_ra_meta_pages(sbi, set->set, 1,
+ META_NAT, true);
+ }
+ }
+ }
+
f2fs_down_write(&nm_i->nat_tree_lock);
/*
@@ -3141,21 +3141,13 @@ int f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
nm_i->nat_cnt[DIRTY_NAT], NAT_JOURNAL))
remove_nats_in_journal(sbi);
- while ((found = __gang_lookup_nat_set(nm_i,
- set_idx, NAT_VEC_SIZE, setvec))) {
- unsigned idx;
-
- set_idx = setvec[found - 1]->set + 1;
- for (idx = 0; idx < found; idx++)
- __adjust_nat_entry_set(setvec[idx], &sets,
- MAX_NAT_JENTRIES(journal));
- }
-
/* flush dirty nats in nat entry set */
- list_for_each_entry_safe(set, tmp, &sets, set_list) {
- err = __flush_nat_entry_set(sbi, set, cpc);
- if (err)
- break;
+ for (i = 0; i <= NAT_ENTRY_PER_BLOCK; i++) {
+ list_for_each_entry_safe(set, tmp, &nm_i->nat_dirty_set[i], set_list) {
+ err = __flush_nat_entry_set(sbi, set, cpc);
+ if (err)
+ break;
+ }
}
f2fs_up_write(&nm_i->nat_tree_lock);
@@ -3249,6 +3241,7 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
struct f2fs_nm_info *nm_i = NM_I(sbi);
unsigned char *version_bitmap;
unsigned int nat_segs;
+ int i;
int err;
nm_i->nat_blkaddr = le32_to_cpu(sb_raw->nat_blkaddr);
@@ -3275,6 +3268,9 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
INIT_LIST_HEAD(&nm_i->nat_entries);
spin_lock_init(&nm_i->nat_list_lock);
+ for (i = 0; i <= NAT_ENTRY_PER_BLOCK; i++)
+ INIT_LIST_HEAD(&nm_i->nat_dirty_set[i]);
+
mutex_init(&nm_i->build_lock);
spin_lock_init(&nm_i->nid_list_lock);
init_f2fs_rwsem(&nm_i->nat_tree_lock);
diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 030390543..d805d4ce7 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -158,7 +158,7 @@ enum mem_type {
};
struct nat_entry_set {
- struct list_head set_list; /* link with other nat sets */
+ struct list_head set_list; /* link with nat sets which have same entry_cnt */
struct list_head entry_list; /* link with dirty nat entries */
nid_t set; /* set number*/
unsigned int entry_cnt; /* the # of nat entries in set */
--
2.25.1
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