f2fs: add bitmaps for empty or full NAT blocks

This patches adds bitmaps to represent empty or full NAT blocks containing
free nid entries.

If we can find valid crc|cp_ver in the last block of checkpoint pack, we'll
use these bitmaps when building free nids. In order to avoid checkpointing
burden, up-to-date bitmaps will be flushed only during umount time. So,
normally we can get this gain, but when power-cut happens, we rely on fsck.f2fs
which recovers this bitmap again.

After this patch, we build free nids from nid #0 at mount time to make more
full NAT blocks, but in runtime, we check empty NAT blocks to load free nids
without loading any NAT pages from disk.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

6 files changed, 231 insertions, 20 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 042f8d9afe44..cd7132121573 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1024,6 +1024,10 @@ static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
         spin_lock(&sbi->cp_lock);
 
+        if (cpc->reason == CP_UMOUNT && ckpt->cp_pack_total_block_count >
+                        sbi->blocks_per_seg - NM_I(sbi)->nat_bits_blocks)
+                disable_nat_bits(sbi, false);
+
         if (cpc->reason == CP_UMOUNT)
                 __set_ckpt_flags(ckpt, CP_UMOUNT_FLAG);
         else
@@ -1136,6 +1140,28 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
         start_blk = __start_cp_next_addr(sbi);
 
+        /* write nat bits */
+        if (enabled_nat_bits(sbi, cpc)) {
+                __u64 cp_ver = cur_cp_version(ckpt);
+                unsigned int i;
+                block_t blk;
+
+                cp_ver |= ((__u64)crc32 << 32);
+                *(__le64 *)nm_i->nat_bits = cpu_to_le64(cp_ver);
+
+                blk = start_blk + sbi->blocks_per_seg - nm_i->nat_bits_blocks;
+                for (i = 0; i < nm_i->nat_bits_blocks; i++)
+                        update_meta_page(sbi, nm_i->nat_bits +
+                                        (i << F2FS_BLKSIZE_BITS), blk + i);
+
+                /* Flush all the NAT BITS pages */
+                while (get_pages(sbi, F2FS_DIRTY_META)) {
+                        sync_meta_pages(sbi, META, LONG_MAX);
+                        if (unlikely(f2fs_cp_error(sbi)))
+                                return -EIO;
+                }
+        }
+
         /* need to wait for end_io results */
         wait_on_all_pages_writeback(sbi);
         if (unlikely(f2fs_cp_error(sbi)))
@@ -1272,7 +1298,7 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
         ckpt->checkpoint_ver = cpu_to_le64(++ckpt_ver);
 
         /* write cached NAT/SIT entries to NAT/SIT area */
-        flush_nat_entries(sbi);
+        flush_nat_entries(sbi, cpc);
         flush_sit_entries(sbi, cpc);
 
         /* unlock all the fs_lock[] in do_checkpoint() */
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index de8da9fc5c99..015ad2b73a92 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -193,6 +193,7 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
         /* build nm */
         si->base_mem += sizeof(struct f2fs_nm_info);
         si->base_mem += __bitmap_size(sbi, NAT_BITMAP);
+        si->base_mem += (NM_I(sbi)->nat_bits_blocks << F2FS_BLKSIZE_BITS);
 
 get_cache:
         si->cache_mem = 0;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e26cc6909a54..d1156cdd211e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -554,6 +554,7 @@ struct f2fs_nm_info {
         struct list_head nat_entries;   /* cached nat entry list (clean) */
         unsigned int nat_cnt;           /* the # of cached nat entries */
         unsigned int dirty_nat_cnt;     /* total num of nat entries in set */
+        unsigned int nat_blocks;        /* # of nat blocks */
 
         /* free node ids management */
         struct radix_tree_root free_nid_root;/* root of the free_nid cache */
@@ -564,6 +565,11 @@ struct f2fs_nm_info {
 
         /* for checkpoint */
         char *nat_bitmap;               /* NAT bitmap pointer */
+
+        unsigned int nat_bits_blocks;   /* # of nat bits blocks */
+        unsigned char *nat_bits;        /* NAT bits blocks */
+        unsigned char *full_nat_bits;   /* full NAT pages */
+        unsigned char *empty_nat_bits;  /* empty NAT pages */
 #ifdef CONFIG_F2FS_CHECK_FS
         char *nat_bitmap_mir;           /* NAT bitmap mirror */
 #endif
@@ -1171,6 +1177,27 @@ static inline void clear_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
         spin_unlock(&sbi->cp_lock);
 }
 
+static inline void disable_nat_bits(struct f2fs_sb_info *sbi, bool lock)
+{
+        set_sbi_flag(sbi, SBI_NEED_FSCK);
+
+        if (lock)
+                spin_lock(&sbi->cp_lock);
+        __clear_ckpt_flags(F2FS_CKPT(sbi), CP_NAT_BITS_FLAG);
+        kfree(NM_I(sbi)->nat_bits);
+        NM_I(sbi)->nat_bits = NULL;
+        if (lock)
+                spin_unlock(&sbi->cp_lock);
+}
+
+static inline bool enabled_nat_bits(struct f2fs_sb_info *sbi,
+                                        struct cp_control *cpc)
+{
+        bool set = is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG);
+
+        return (cpc) ? (cpc->reason == CP_UMOUNT) && set : set;
+}
+
 static inline void f2fs_lock_op(struct f2fs_sb_info *sbi)
 {
         down_read(&sbi->cp_rwsem);
@@ -2131,7 +2158,7 @@ void move_node_page(struct page *node_page, int gc_type);
 int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
                         struct writeback_control *wbc, bool atomic);
 int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc);
-void build_free_nids(struct f2fs_sb_info *sbi, bool sync);
+void build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount);
 bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid);
 void alloc_nid_done(struct f2fs_sb_info *sbi, nid_t nid);
 void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid);
@@ -2142,7 +2169,7 @@ int recover_xattr_data(struct inode *inode, struct page *page,
 int recover_inode_page(struct f2fs_sb_info *sbi, struct page *page);
 int restore_node_summary(struct f2fs_sb_info *sbi,
                         unsigned int segno, struct f2fs_summary_block *sum);
-void flush_nat_entries(struct f2fs_sb_info *sbi);
+void flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc);
 int build_node_manager(struct f2fs_sb_info *sbi);
 void destroy_node_manager(struct f2fs_sb_info *sbi);
 int __init create_node_manager_caches(void);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 8ebc4c78e6a4..43d35ec11851 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -338,6 +338,9 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
                 set_nat_flag(e, IS_CHECKPOINTED, false);
         __set_nat_cache_dirty(nm_i, e);
 
+        if (enabled_nat_bits(sbi, NULL) && new_blkaddr == NEW_ADDR)
+                clear_bit_le(NAT_BLOCK_OFFSET(ni->nid), nm_i->empty_nat_bits);
+
         /* update fsync_mark if its inode nat entry is still alive */
         if (ni->nid != ni->ino)
                 e = __lookup_nat_cache(nm_i, ni->ino);
@@ -1841,7 +1844,60 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
         }
 }
 
-static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync)
+static int scan_nat_bits(struct f2fs_sb_info *sbi)
+{
+        struct f2fs_nm_info *nm_i = NM_I(sbi);
+        struct page *page;
+        unsigned int i = 0;
+        nid_t target = FREE_NID_PAGES * NAT_ENTRY_PER_BLOCK;
+        nid_t nid;
+
+        if (!enabled_nat_bits(sbi, NULL))
+                return -EAGAIN;
+
+        down_read(&nm_i->nat_tree_lock);
+check_empty:
+        i = find_next_bit_le(nm_i->empty_nat_bits, nm_i->nat_blocks, i);
+        if (i >= nm_i->nat_blocks) {
+                i = 0;
+                goto check_partial;
+        }
+
+        for (nid = i * NAT_ENTRY_PER_BLOCK; nid < (i + 1) * NAT_ENTRY_PER_BLOCK;
+                                                                        nid++) {
+                if (unlikely(nid >= nm_i->max_nid))
+                        break;
+                add_free_nid(sbi, nid, true);
+        }
+
+        if (nm_i->nid_cnt[FREE_NID_LIST] >= target)
+                goto out;
+        i++;
+        goto check_empty;
+
+check_partial:
+        i = find_next_zero_bit_le(nm_i->full_nat_bits, nm_i->nat_blocks, i);
+        if (i >= nm_i->nat_blocks) {
+                disable_nat_bits(sbi, true);
+                up_read(&nm_i->nat_tree_lock);
+                return -EINVAL;
+        }
+
+        nid = i * NAT_ENTRY_PER_BLOCK;
+        page = get_current_nat_page(sbi, nid);
+        scan_nat_page(sbi, page, nid);
+        f2fs_put_page(page, 1);
+
+        if (nm_i->nid_cnt[FREE_NID_LIST] < target) {
+                i++;
+                goto check_partial;
+        }
+out:
+        up_read(&nm_i->nat_tree_lock);
+        return 0;
+}
+
+static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
 {
         struct f2fs_nm_info *nm_i = NM_I(sbi);
         struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
@@ -1856,6 +1912,21 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync)
         if (!sync && !available_free_memory(sbi, FREE_NIDS))
                 return;
 
+        /* try to find free nids with nat_bits */
+        if (!mount && !scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
+                return;
+
+        /* find next valid candidate */
+        if (enabled_nat_bits(sbi, NULL)) {
+                int idx = find_next_zero_bit_le(nm_i->full_nat_bits,
+                                        nm_i->nat_blocks, 0);
+
+                if (idx >= nm_i->nat_blocks)
+                        set_sbi_flag(sbi, SBI_NEED_FSCK);
+                else
+                        nid = idx * NAT_ENTRY_PER_BLOCK;
+        }
+
         /* readahead nat pages to be scanned */
         ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), FREE_NID_PAGES,
                                                         META_NAT, true);
@@ -1898,10 +1969,10 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync)
                                         nm_i->ra_nid_pages, META_NAT, false);
 }
 
-void build_free_nids(struct f2fs_sb_info *sbi, bool sync)
+void build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
 {
         mutex_lock(&NM_I(sbi)->build_lock);
-        __build_free_nids(sbi, sync);
+        __build_free_nids(sbi, sync, mount);
         mutex_unlock(&NM_I(sbi)->build_lock);
 }
 
@@ -1943,7 +2014,7 @@ retry:
         spin_unlock(&nm_i->nid_list_lock);
 
         /* Let's scan nat pages and its caches to get free nids */
-        build_free_nids(sbi, true);
+        build_free_nids(sbi, true, false);
         goto retry;
 }
 
@@ -2235,8 +2306,39 @@ add_out:
         list_add_tail(&nes->set_list, head);
 }
 
+void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
+                                                struct page *page)
+{
+        struct f2fs_nm_info *nm_i = NM_I(sbi);
+        unsigned int nat_index = start_nid / NAT_ENTRY_PER_BLOCK;
+        struct f2fs_nat_block *nat_blk = page_address(page);
+        int valid = 0;
+        int i;
+
+        if (!enabled_nat_bits(sbi, NULL))
+                return;
+
+        for (i = 0; i < NAT_ENTRY_PER_BLOCK; i++) {
+                if (start_nid == 0 && i == 0)
+                        valid++;
+                if (nat_blk->entries[i].block_addr)
+                        valid++;
+        }
+        if (valid == 0) {
+                set_bit_le(nat_index, nm_i->empty_nat_bits);
+                clear_bit_le(nat_index, nm_i->full_nat_bits);
+                return;
+        }
+
+        clear_bit_le(nat_index, nm_i->empty_nat_bits);
+        if (valid == NAT_ENTRY_PER_BLOCK)
+                set_bit_le(nat_index, nm_i->full_nat_bits);
+        else
+                clear_bit_le(nat_index, nm_i->full_nat_bits);
+}
+
 static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
-                                        struct nat_entry_set *set)
+                struct nat_entry_set *set, struct cp_control *cpc)
 {
         struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
         struct f2fs_journal *journal = curseg->journal;
@@ -2251,7 +2353,8 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
          * #1, flush nat entries to journal in current hot data summary block.
          * #2, flush nat entries to nat page.
          */
-        if (!__has_cursum_space(journal, set->entry_cnt, NAT_JOURNAL))
+        if (enabled_nat_bits(sbi, cpc) ||
+                !__has_cursum_space(journal, set->entry_cnt, NAT_JOURNAL))
                 to_journal = false;
 
         if (to_journal) {
@@ -2291,10 +2394,12 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
                 }
         }
 
-        if (to_journal)
+        if (to_journal) {
                 up_write(&curseg->journal_rwsem);
-        else
+        } else {
+                __update_nat_bits(sbi, start_nid, page);
                 f2fs_put_page(page, 1);
+        }
 
         f2fs_bug_on(sbi, set->entry_cnt);
 
@@ -2305,7 +2410,7 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 /*
  * This function is called during the checkpointing process.
  */
-void flush_nat_entries(struct f2fs_sb_info *sbi)
+void 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);
@@ -2326,7 +2431,8 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
          * entries, remove all entries from journal and merge them
          * into nat entry set.
          */
-        if (!__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
+        if (cpc->reason == CP_UMOUNT ||
+                !__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
                 remove_nats_in_journal(sbi);
 
         while ((found = __gang_lookup_nat_set(nm_i,
@@ -2340,27 +2446,72 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 
         /* flush dirty nats in nat entry set */
         list_for_each_entry_safe(set, tmp, &sets, set_list)
-                __flush_nat_entry_set(sbi, set);
+                __flush_nat_entry_set(sbi, set, cpc);
 
         up_write(&nm_i->nat_tree_lock);
 
         f2fs_bug_on(sbi, nm_i->dirty_nat_cnt);
 }
 
+static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
+{
+        struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
+        struct f2fs_nm_info *nm_i = NM_I(sbi);
+        unsigned int nat_bits_bytes = nm_i->nat_blocks / BITS_PER_BYTE;
+        unsigned int i;
+        __u64 cp_ver = cur_cp_version(ckpt);
+        size_t crc_offset = le32_to_cpu(ckpt->checksum_offset);
+        __u64 crc = le32_to_cpu(*((__le32 *)
+                                ((unsigned char *)ckpt + crc_offset)));
+        block_t nat_bits_addr;
+
+        if (!enabled_nat_bits(sbi, NULL))
+                return 0;
+
+        nm_i->nat_bits_blocks = F2FS_BYTES_TO_BLK((nat_bits_bytes << 1) + 8 +
+                                                F2FS_BLKSIZE - 1);
+        nm_i->nat_bits = kzalloc(nm_i->nat_bits_blocks << F2FS_BLKSIZE_BITS,
+                                                GFP_KERNEL);
+        if (!nm_i->nat_bits)
+                return -ENOMEM;
+
+        nat_bits_addr = __start_cp_addr(sbi) + sbi->blocks_per_seg -
+                                                nm_i->nat_bits_blocks;
+        for (i = 0; i < nm_i->nat_bits_blocks; i++) {
+                struct page *page = get_meta_page(sbi, nat_bits_addr++);
+
+                memcpy(nm_i->nat_bits + (i << F2FS_BLKSIZE_BITS),
+                                        page_address(page), F2FS_BLKSIZE);
+                f2fs_put_page(page, 1);
+        }
+
+        cp_ver |= (crc << 32);
+        if (cpu_to_le64(cp_ver) != *(__le64 *)nm_i->nat_bits) {
+                disable_nat_bits(sbi, true);
+                return 0;
+        }
+
+        nm_i->full_nat_bits = nm_i->nat_bits + 8;
+        nm_i->empty_nat_bits = nm_i->full_nat_bits + nat_bits_bytes;
+
+        f2fs_msg(sbi->sb, KERN_NOTICE, "Found nat_bits in checkpoint");
+        return 0;
+}
+
 static int init_node_manager(struct f2fs_sb_info *sbi)
 {
         struct f2fs_super_block *sb_raw = F2FS_RAW_SUPER(sbi);
         struct f2fs_nm_info *nm_i = NM_I(sbi);
         unsigned char *version_bitmap;
-        unsigned int nat_segs, nat_blocks;
+        unsigned int nat_segs;
+        int err;
 
         nm_i->nat_blkaddr = le32_to_cpu(sb_raw->nat_blkaddr);
 
         /* segment_count_nat includes pair segment so divide to 2. */
         nat_segs = le32_to_cpu(sb_raw->segment_count_nat) >> 1;
-        nat_blocks = nat_segs << le32_to_cpu(sb_raw->log_blocks_per_seg);
-
-        nm_i->max_nid = NAT_ENTRY_PER_BLOCK * nat_blocks;
+        nm_i->nat_blocks = nat_segs << le32_to_cpu(sb_raw->log_blocks_per_seg);
+        nm_i->max_nid = NAT_ENTRY_PER_BLOCK * nm_i->nat_blocks;
 
         /* not used nids: 0, node, meta, (and root counted as valid node) */
         nm_i->available_nids = nm_i->max_nid - sbi->total_valid_node_count -
@@ -2394,6 +2545,10 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
         if (!nm_i->nat_bitmap)
                 return -ENOMEM;
 
+        err = __get_nat_bitmaps(sbi);
+        if (err)
+                return err;
+
 #ifdef CONFIG_F2FS_CHECK_FS
         nm_i->nat_bitmap_mir = kmemdup(version_bitmap, nm_i->bitmap_size,
                                         GFP_KERNEL);
@@ -2416,7 +2571,7 @@ int build_node_manager(struct f2fs_sb_info *sbi)
         if (err)
                 return err;
 
-        build_free_nids(sbi, true);
+        build_free_nids(sbi, true, true);
         return 0;
 }
 
@@ -2475,6 +2630,7 @@ void destroy_node_manager(struct f2fs_sb_info *sbi)
         up_write(&nm_i->nat_tree_lock);
 
         kfree(nm_i->nat_bitmap);
+        kfree(nm_i->nat_bits);
 #ifdef CONFIG_F2FS_CHECK_FS
         kfree(nm_i->nat_bitmap_mir);
 #endif
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 3e95db5375ed..9eb6d89bf9e2 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -386,7 +386,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
         if (!available_free_memory(sbi, FREE_NIDS))
                 try_to_free_nids(sbi, MAX_FREE_NIDS);
         else
-                build_free_nids(sbi, false);
+                build_free_nids(sbi, false, false);
 
         if (!is_idle(sbi))
                 return;
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index f0748524ca8c..1c92ace2e8f8 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -114,6 +114,7 @@ struct f2fs_super_block {
 /*
  * For checkpoint
  */
+#define CP_NAT_BITS_FLAG        0x00000080
 #define CP_CRC_RECOVERY_FLAG    0x00000040
 #define CP_FASTBOOT_FLAG        0x00000020
 #define CP_FSCK_FLAG            0x00000010