This patch introduces __count_free_nids/try_to_free_nids and registers
them in slab shrinker for shrinking under memory pressure.

Signed-off-by: Chao Yu <chao2...@samsung.com>
---
 fs/f2fs/f2fs.h     |  1 +
 fs/f2fs/node.c     | 26 ++++++++++++++++++++++++++
 fs/f2fs/segment.c  |  3 +++
 fs/f2fs/shrinker.c | 14 ++++++++++++++
 4 files changed, 44 insertions(+)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d0b294f..9052bd2 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1682,6 +1682,7 @@ int sync_node_pages(struct f2fs_sb_info *, nid_t, struct 
writeback_control *);
 bool alloc_nid(struct f2fs_sb_info *, nid_t *);
 void alloc_nid_done(struct f2fs_sb_info *, nid_t);
 void alloc_nid_failed(struct f2fs_sb_info *, nid_t);
+int try_to_free_nids(struct f2fs_sb_info *, int);
 void recover_inline_xattr(struct inode *, struct page *);
 void recover_xattr_data(struct inode *, struct page *, block_t);
 int recover_inode_page(struct f2fs_sb_info *, struct page *);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index ac91107..bb0a4d5 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1635,6 +1635,32 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t 
nid)
                kmem_cache_free(free_nid_slab, i);
 }
 
+int try_to_free_nids(struct f2fs_sb_info *sbi, int nr_shrink)
+{
+       struct f2fs_nm_info *nm_i = NM_I(sbi);
+       int nr = nr_shrink;
+
+       if (!mutex_trylock(&nm_i->build_lock))
+               return 0;
+
+       spin_lock(&nm_i->free_nid_list_lock);
+       while (nr_shrink && nm_i->fcnt > NAT_ENTRY_PER_BLOCK) {
+               struct free_nid *i;
+
+               i = list_first_entry(&nm_i->free_nid_list,
+                                       struct free_nid, list);
+               f2fs_bug_on(sbi, i->state == NID_ALLOC);
+               __del_from_free_nid_list(nm_i, i);
+               nm_i->fcnt--;
+               kmem_cache_free(free_nid_slab, i);
+               nr_shrink--;
+       }
+       spin_unlock(&nm_i->free_nid_list_lock);
+       mutex_unlock(&nm_i->build_lock);
+
+       return nr - nr_shrink;
+}
+
 void recover_inline_xattr(struct inode *inode, struct page *page)
 {
        void *src_addr, *dst_addr;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 08b2ebc..85c0433 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -310,6 +310,9 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
        if (!available_free_memory(sbi, NAT_ENTRIES))
                try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK);
 
+       if (!available_free_memory(sbi, FREE_NIDS))
+               try_to_free_nids(sbi, NAT_ENTRY_PER_BLOCK * FREE_NID_PAGES);
+
        /* checkpoint is the only way to shrink partial cached entries */
        if (!available_free_memory(sbi, NAT_ENTRIES) ||
                        excess_prefree_segs(sbi) ||
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index 9aa4235..da0d8e0 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -23,6 +23,13 @@ static unsigned long __count_nat_entries(struct f2fs_sb_info 
*sbi)
        return NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
 }
 
+static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
+{
+       if (NM_I(sbi)->fcnt > NAT_ENTRY_PER_BLOCK)
+               return NM_I(sbi)->fcnt - NAT_ENTRY_PER_BLOCK;
+       return 0;
+}
+
 static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
 {
        return sbi->total_ext_tree + atomic_read(&sbi->total_ext_node);
@@ -53,6 +60,9 @@ unsigned long f2fs_shrink_count(struct shrinker *shrink,
                /* shrink clean nat cache entries */
                count += __count_nat_entries(sbi);
 
+               /* count free nids cache entries */
+               count += __count_free_nids(sbi);
+
                spin_lock(&f2fs_list_lock);
                p = p->next;
                mutex_unlock(&sbi->umount_mutex);
@@ -97,6 +107,10 @@ unsigned long f2fs_shrink_scan(struct shrinker *shrink,
                if (freed < nr)
                        freed += try_to_free_nats(sbi, nr - freed);
 
+               /* shrink free nids cache entries */
+               if (freed < nr)
+                       freed += try_to_free_nids(sbi, nr - freed);
+
                spin_lock(&f2fs_list_lock);
                p = p->next;
                list_move_tail(&sbi->s_list, &f2fs_list);
-- 
2.4.2


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