1 files changed, 232 insertions, 258 deletions

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 8c1097327abc..0254be2d73c6 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -35,8 +35,7 @@
 #include "segbuf.h"
 
 
-static LIST_HEAD(nilfs_objects);
-static DEFINE_SPINLOCK(nilfs_lock);
+static int nilfs_valid_sb(struct nilfs_super_block *sbp);
 
 void nilfs_set_last_segment(struct the_nilfs *nilfs,
 			    sector_t start_blocknr, u64 seq, __u64 cno)
@@ -45,20 +44,27 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
 	nilfs->ns_last_pseg = start_blocknr;
 	nilfs->ns_last_seq = seq;
 	nilfs->ns_last_cno = cno;
+
+	if (!nilfs_sb_dirty(nilfs)) {
+		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
+			goto stay_cursor;
+
+		set_nilfs_sb_dirty(nilfs);
+	}
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+
+ stay_cursor:
 	spin_unlock(&nilfs->ns_last_segment_lock);
 }
 
 /**
- * alloc_nilfs - allocate the_nilfs structure
+ * alloc_nilfs - allocate a nilfs object
  * @bdev: block device to which the_nilfs is related
  *
- * alloc_nilfs() allocates memory for the_nilfs and
- * initializes its reference count and locks.
- *
  * Return Value: On success, pointer to the_nilfs is returned.
  * On error, NULL is returned.
  */
-static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
+struct the_nilfs *alloc_nilfs(struct block_device *bdev)
 {
 	struct the_nilfs *nilfs;
 
@@ -67,92 +73,25 @@ static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
 		return NULL;
 
 	nilfs->ns_bdev = bdev;
-	atomic_set(&nilfs->ns_count, 1);
 	atomic_set(&nilfs->ns_ndirtyblks, 0);
 	init_rwsem(&nilfs->ns_sem);
-	init_rwsem(&nilfs->ns_super_sem);
-	mutex_init(&nilfs->ns_mount_mutex);
-	init_rwsem(&nilfs->ns_writer_sem);
-	INIT_LIST_HEAD(&nilfs->ns_list);
-	INIT_LIST_HEAD(&nilfs->ns_supers);
+	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
 	spin_lock_init(&nilfs->ns_last_segment_lock);
-	nilfs->ns_gc_inodes_h = NULL;
+	nilfs->ns_cptree = RB_ROOT;
+	spin_lock_init(&nilfs->ns_cptree_lock);
 	init_rwsem(&nilfs->ns_segctor_sem);
 
 	return nilfs;
 }
 
 /**
- * find_or_create_nilfs - find or create nilfs object
- * @bdev: block device to which the_nilfs is related
- *
- * find_nilfs() looks up an existent nilfs object created on the
- * device and gets the reference count of the object.  If no nilfs object
- * is found on the device, a new nilfs object is allocated.
- *
- * Return Value: On success, pointer to the nilfs object is returned.
- * On error, NULL is returned.
+ * destroy_nilfs - destroy nilfs object
+ * @nilfs: nilfs object to be released
  */
-struct the_nilfs *find_or_create_nilfs(struct block_device *bdev)
+void destroy_nilfs(struct the_nilfs *nilfs)
 {
-	struct the_nilfs *nilfs, *new = NULL;
-
- retry:
-	spin_lock(&nilfs_lock);
-	list_for_each_entry(nilfs, &nilfs_objects, ns_list) {
-		if (nilfs->ns_bdev == bdev) {
-			get_nilfs(nilfs);
-			spin_unlock(&nilfs_lock);
-			if (new)
-				put_nilfs(new);
-			return nilfs; /* existing object */
-		}
-	}
-	if (new) {
-		list_add_tail(&new->ns_list, &nilfs_objects);
-		spin_unlock(&nilfs_lock);
-		return new; /* new object */
-	}
-	spin_unlock(&nilfs_lock);
-
-	new = alloc_nilfs(bdev);
-	if (new)
-		goto retry;
-	return NULL; /* insufficient memory */
-}
-
-/**
- * put_nilfs - release a reference to the_nilfs
- * @nilfs: the_nilfs structure to be released
- *
- * put_nilfs() decrements a reference counter of the_nilfs.
- * If the reference count reaches zero, the_nilfs is freed.
- */
-void put_nilfs(struct the_nilfs *nilfs)
-{
-	spin_lock(&nilfs_lock);
-	if (!atomic_dec_and_test(&nilfs->ns_count)) {
-		spin_unlock(&nilfs_lock);
-		return;
-	}
-	list_del_init(&nilfs->ns_list);
-	spin_unlock(&nilfs_lock);
-
-	/*
-	 * Increment of ns_count never occurs below because the caller
-	 * of get_nilfs() holds at least one reference to the_nilfs.
-	 * Thus its exclusion control is not required here.
-	 */
-
 	might_sleep();
-	if (nilfs_loaded(nilfs)) {
-		nilfs_mdt_destroy(nilfs->ns_sufile);
-		nilfs_mdt_destroy(nilfs->ns_cpfile);
-		nilfs_mdt_destroy(nilfs->ns_dat);
-		nilfs_mdt_destroy(nilfs->ns_gc_dat);
-	}
 	if (nilfs_init(nilfs)) {
-		nilfs_destroy_gccache(nilfs);
 		brelse(nilfs->ns_sbh[0]);
 		brelse(nilfs->ns_sbh[1]);
 	}
@@ -160,16 +99,17 @@ void put_nilfs(struct the_nilfs *nilfs)
 }
 
 static int nilfs_load_super_root(struct the_nilfs *nilfs,
-				 struct nilfs_sb_info *sbi, sector_t sr_block)
+				 struct super_block *sb, sector_t sr_block)
 {
 	struct buffer_head *bh_sr;
 	struct nilfs_super_root *raw_sr;
 	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	struct nilfs_inode *rawi;
 	unsigned dat_entry_size, segment_usage_size, checkpoint_size;
 	unsigned inode_size;
 	int err;
 
-	err = nilfs_read_super_root_block(sbi->s_super, sr_block, &bh_sr, 1);
+	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
 	if (unlikely(err))
 		return err;
 
@@ -181,40 +121,22 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 
 	inode_size = nilfs->ns_inode_size;
 
-	err = -ENOMEM;
-	nilfs->ns_dat = nilfs_dat_new(nilfs, dat_entry_size);
-	if (unlikely(!nilfs->ns_dat))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_DAT_OFFSET(inode_size);
+	err = nilfs_dat_read(sb, dat_entry_size, rawi, &nilfs->ns_dat);
+	if (err)
 		goto failed;
 
-	nilfs->ns_gc_dat = nilfs_dat_new(nilfs, dat_entry_size);
-	if (unlikely(!nilfs->ns_gc_dat))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_CPFILE_OFFSET(inode_size);
+	err = nilfs_cpfile_read(sb, checkpoint_size, rawi, &nilfs->ns_cpfile);
+	if (err)
 		goto failed_dat;
 
-	nilfs->ns_cpfile = nilfs_cpfile_new(nilfs, checkpoint_size);
-	if (unlikely(!nilfs->ns_cpfile))
-		goto failed_gc_dat;
-
-	nilfs->ns_sufile = nilfs_sufile_new(nilfs, segment_usage_size);
-	if (unlikely(!nilfs->ns_sufile))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_SUFILE_OFFSET(inode_size);
+	err = nilfs_sufile_read(sb, segment_usage_size, rawi,
+				&nilfs->ns_sufile);
+	if (err)
 		goto failed_cpfile;
 
-	nilfs_mdt_set_shadow(nilfs->ns_dat, nilfs->ns_gc_dat);
-
-	err = nilfs_dat_read(nilfs->ns_dat, (void *)bh_sr->b_data +
-			     NILFS_SR_DAT_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
-	err = nilfs_cpfile_read(nilfs->ns_cpfile, (void *)bh_sr->b_data +
-				NILFS_SR_CPFILE_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
-	err = nilfs_sufile_read(nilfs->ns_sufile, (void *)bh_sr->b_data +
-				NILFS_SR_SUFILE_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
 	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
 	nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);
 
@@ -222,17 +144,11 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 	brelse(bh_sr);
 	return err;
 
- failed_sufile:
-	nilfs_mdt_destroy(nilfs->ns_sufile);
-
  failed_cpfile:
-	nilfs_mdt_destroy(nilfs->ns_cpfile);
-
- failed_gc_dat:
-	nilfs_mdt_destroy(nilfs->ns_gc_dat);
+	iput(nilfs->ns_cpfile);
 
  failed_dat:
-	nilfs_mdt_destroy(nilfs->ns_dat);
+	iput(nilfs->ns_dat);
 	goto failed;
 }
 
@@ -248,6 +164,37 @@ static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
 }
 
 /**
+ * nilfs_store_log_cursor - load log cursor from a super block
+ * @nilfs: nilfs object
+ * @sbp: buffer storing super block to be read
+ *
+ * nilfs_store_log_cursor() reads the last position of the log
+ * containing a super root from a given super block, and initializes
+ * relevant information on the nilfs object preparatory for log
+ * scanning and recovery.
+ */
+static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
+				  struct nilfs_super_block *sbp)
+{
+	int ret = 0;
+
+	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
+	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
+	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
+
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+	nilfs->ns_seg_seq = nilfs->ns_last_seq;
+	nilfs->ns_segnum =
+		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
+	nilfs->ns_cno = nilfs->ns_last_cno + 1;
+	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
+		printk(KERN_ERR "NILFS invalid last segment number.\n");
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+/**
  * load_nilfs - load and recover the nilfs
  * @nilfs: the_nilfs structure to be released
  * @sbi: nilfs_sb_info used to recover past segment
@@ -264,15 +211,6 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 	int valid_fs = nilfs_valid_fs(nilfs);
 	int err;
 
-	if (nilfs_loaded(nilfs)) {
-		if (valid_fs ||
-		    ((s_flags & MS_RDONLY) && nilfs_test_opt(sbi, NORECOVERY)))
-			return 0;
-		printk(KERN_ERR "NILFS: the filesystem is in an incomplete "
-		       "recovery state.\n");
-		return -EINVAL;
-	}
-
 	if (!valid_fs) {
 		printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
 		if (s_flags & MS_RDONLY) {
@@ -285,13 +223,55 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 
 	nilfs_init_recovery_info(&ri);
 
-	err = nilfs_search_super_root(nilfs, sbi, &ri);
+	err = nilfs_search_super_root(nilfs, &ri);
 	if (unlikely(err)) {
-		printk(KERN_ERR "NILFS: error searching super root.\n");
-		goto failed;
+		struct nilfs_super_block **sbp = nilfs->ns_sbp;
+		int blocksize;
+
+		if (err != -EINVAL)
+			goto scan_error;
+
+		if (!nilfs_valid_sb(sbp[1])) {
+			printk(KERN_WARNING
+			       "NILFS warning: unable to fall back to spare"
+			       "super block\n");
+			goto scan_error;
+		}
+		printk(KERN_INFO
+		       "NILFS: try rollback from an earlier position\n");
+
+		/*
+		 * restore super block with its spare and reconfigure
+		 * relevant states of the nilfs object.
+		 */
+		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
+		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
+
+		/* verify consistency between two super blocks */
+		blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
+		if (blocksize != nilfs->ns_blocksize) {
+			printk(KERN_WARNING
+			       "NILFS warning: blocksize differs between "
+			       "two super blocks (%d != %d)\n",
+			       blocksize, nilfs->ns_blocksize);
+			goto scan_error;
+		}
+
+		err = nilfs_store_log_cursor(nilfs, sbp[0]);
+		if (err)
+			goto scan_error;
+
+		/* drop clean flag to allow roll-forward and recovery */
+		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
+		valid_fs = 0;
+
+		err = nilfs_search_super_root(nilfs, &ri);
+		if (err)
+			goto scan_error;
 	}
 
-	err = nilfs_load_super_root(nilfs, sbi, ri.ri_super_root);
+	err = nilfs_load_super_root(nilfs, sbi->s_super, ri.ri_super_root);
 	if (unlikely(err)) {
 		printk(KERN_ERR "NILFS: error loading super root.\n");
 		goto failed;
@@ -301,11 +281,23 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto skip_recovery;
 
 	if (s_flags & MS_RDONLY) {
+		__u64 features;
+
 		if (nilfs_test_opt(sbi, NORECOVERY)) {
 			printk(KERN_INFO "NILFS: norecovery option specified. "
 			       "skipping roll-forward recovery\n");
 			goto skip_recovery;
 		}
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		if (features) {
+			printk(KERN_ERR "NILFS: couldn't proceed with "
+			       "recovery because of unsupported optional "
+			       "features (%llx)\n",
+			       (unsigned long long)features);
+			err = -EROFS;
+			goto failed_unload;
+		}
 		if (really_read_only) {
 			printk(KERN_ERR "NILFS: write access "
 			       "unavailable, cannot proceed.\n");
@@ -320,14 +312,13 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto failed_unload;
 	}
 
-	err = nilfs_recover_logical_segments(nilfs, sbi, &ri);
+	err = nilfs_salvage_orphan_logs(nilfs, sbi, &ri);
 	if (err)
 		goto failed_unload;
 
 	down_write(&nilfs->ns_sem);
-	nilfs->ns_mount_state |= NILFS_VALID_FS;
-	nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
-	err = nilfs_commit_super(sbi, 1);
+	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
+	err = nilfs_cleanup_super(sbi);
 	up_write(&nilfs->ns_sem);
 
 	if (err) {
@@ -343,10 +334,14 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 	sbi->s_super->s_flags = s_flags;
 	return 0;
 
+ scan_error:
+	printk(KERN_ERR "NILFS: error searching super root.\n");
+	goto failed;
+
  failed_unload:
-	nilfs_mdt_destroy(nilfs->ns_cpfile);
-	nilfs_mdt_destroy(nilfs->ns_sufile);
-	nilfs_mdt_destroy(nilfs->ns_dat);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_dat);
 
  failed:
 	nilfs_clear_recovery_info(&ri);
@@ -368,8 +363,8 @@ static unsigned long long nilfs_max_size(unsigned int blkbits)
 static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
 				   struct nilfs_super_block *sbp)
 {
-	if (le32_to_cpu(sbp->s_rev_level) != NILFS_CURRENT_REV) {
-		printk(KERN_ERR "NILFS: revision mismatch "
+	if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
+		printk(KERN_ERR "NILFS: unsupported revision "
 		       "(superblock rev.=%d.%d, current rev.=%d.%d). "
 		       "Please check the version of mkfs.nilfs.\n",
 		       le32_to_cpu(sbp->s_rev_level),
@@ -509,14 +504,14 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
 		return -EINVAL;
 	}
 
-	if (swp) {
+	if (!valid[!swp])
 		printk(KERN_WARNING "NILFS warning: broken superblock. "
 		       "using spare superblock.\n");
+	if (swp)
 		nilfs_swap_super_block(nilfs);
-	}
 
-	nilfs->ns_sbwtime[0] = le64_to_cpu(sbp[0]->s_wtime);
-	nilfs->ns_sbwtime[1] = valid[!swp] ? le64_to_cpu(sbp[1]->s_wtime) : 0;
+	nilfs->ns_sbwcount = 0;
+	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
 	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
 	*sbpp = sbp[0];
 	return 0;
@@ -531,12 +526,7 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
  *
  * init_nilfs() performs common initialization per block device (e.g.
  * reading the super block, getting disk layout information, initializing
- * shared fields in the_nilfs). It takes on some portion of the jobs
- * typically done by a fill_super() routine. This division arises from
- * the nature that multiple NILFS instances may be simultaneously
- * mounted on a device.
- * For multiple mounts on the same device, only the first mount
- * invokes these tasks.
+ * shared fields in the_nilfs).
  *
  * Return Value: On success, 0 is returned. On error, a negative error
  * code is returned.
@@ -545,30 +535,12 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 {
 	struct super_block *sb = sbi->s_super;
 	struct nilfs_super_block *sbp;
-	struct backing_dev_info *bdi;
 	int blocksize;
 	int err;
 
 	down_write(&nilfs->ns_sem);
-	if (nilfs_init(nilfs)) {
-		/* Load values from existing the_nilfs */
-		sbp = nilfs->ns_sbp[0];
-		err = nilfs_store_magic_and_option(sb, sbp, data);
-		if (err)
-			goto out;
-
-		blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
-		if (sb->s_blocksize != blocksize &&
-		    !sb_set_blocksize(sb, blocksize)) {
-			printk(KERN_ERR "NILFS: blocksize %d unfit to device\n",
-			       blocksize);
-			err = -EINVAL;
-		}
-		sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
-		goto out;
-	}
 
-	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
+	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
 	if (!blocksize) {
 		printk(KERN_ERR "NILFS: unable to set blocksize\n");
 		err = -EINVAL;
@@ -582,7 +554,18 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	if (err)
 		goto failed_sbh;
 
+	err = nilfs_check_feature_compatibility(sb, sbp);
+	if (err)
+		goto failed_sbh;
+
 	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
+	if (blocksize < NILFS_MIN_BLOCK_SIZE ||
+	    blocksize > NILFS_MAX_BLOCK_SIZE) {
+		printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
+		       "filesystem blocksize %d\n", blocksize);
+		err = -EINVAL;
+		goto failed_sbh;
+	}
 	if (sb->s_blocksize != blocksize) {
 		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);
 
@@ -604,6 +587,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 			   when reloading fails. */
 	}
 	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
+	nilfs->ns_blocksize = blocksize;
 
 	err = nilfs_store_disk_layout(nilfs, sbp);
 	if (err)
@@ -613,29 +597,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 
 	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);
 
-	bdi = nilfs->ns_bdev->bd_inode->i_mapping->backing_dev_info;
-	nilfs->ns_bdi = bdi ? : &default_backing_dev_info;
-
-	/* Finding last segment */
-	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
-	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
-	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
-
-	nilfs->ns_seg_seq = nilfs->ns_last_seq;
-	nilfs->ns_segnum =
-		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
-	nilfs->ns_cno = nilfs->ns_last_cno + 1;
-	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
-		printk(KERN_ERR "NILFS invalid last segment number.\n");
-		err = -EINVAL;
-		goto failed_sbh;
-	}
-	/* Dummy values  */
-	nilfs->ns_free_segments_count =
-		nilfs->ns_nsegments - (nilfs->ns_segnum + 1);
-
-	/* Initialize gcinode cache */
-	err = nilfs_init_gccache(nilfs);
+	err = nilfs_store_log_cursor(nilfs, sbp);
 	if (err)
 		goto failed_sbh;
 
@@ -673,8 +635,7 @@ int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
 			ret = blkdev_issue_discard(nilfs->ns_bdev,
 						   start * sects_per_block,
 						   nblocks * sects_per_block,
-						   GFP_NOFS,
-						   BLKDEV_IFL_BARRIER);
+						   GFP_NOFS, 0);
 			if (ret < 0)
 				return ret;
 			nblocks = 0;
@@ -684,7 +645,7 @@ int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
 		ret = blkdev_issue_discard(nilfs->ns_bdev,
 					   start * sects_per_block,
 					   nblocks * sects_per_block,
-					   GFP_NOFS, BLKDEV_IFL_BARRIER);
+					   GFP_NOFS, 0);
 	return ret;
 }
 
@@ -711,79 +672,92 @@ int nilfs_near_disk_full(struct the_nilfs *nilfs)
 	return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;
 }
 
-/**
- * nilfs_find_sbinfo - find existing nilfs_sb_info structure
- * @nilfs: nilfs object
- * @rw_mount: mount type (non-zero value for read/write mount)
- * @cno: checkpoint number (zero for read-only mount)
- *
- * nilfs_find_sbinfo() returns the nilfs_sb_info structure which
- * @rw_mount and @cno (in case of snapshots) matched.  If no instance
- * was found, NULL is returned.  Although the super block instance can
- * be unmounted after this function returns, the nilfs_sb_info struct
- * is kept on memory until nilfs_put_sbinfo() is called.
- */
-struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs,
-					int rw_mount, __u64 cno)
+struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)
 {
-	struct nilfs_sb_info *sbi;
-
-	down_read(&nilfs->ns_super_sem);
-	/*
-	 * The SNAPSHOT flag and sb->s_flags are supposed to be
-	 * protected with nilfs->ns_super_sem.
-	 */
-	sbi = nilfs->ns_current;
-	if (rw_mount) {
-		if (sbi && !(sbi->s_super->s_flags & MS_RDONLY))
-			goto found; /* read/write mount */
-		else
-			goto out;
-	} else if (cno == 0) {
-		if (sbi && (sbi->s_super->s_flags & MS_RDONLY))
-			goto found; /* read-only mount */
-		else
-			goto out;
+	struct rb_node *n;
+	struct nilfs_root *root;
+
+	spin_lock(&nilfs->ns_cptree_lock);
+	n = nilfs->ns_cptree.rb_node;
+	while (n) {
+		root = rb_entry(n, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			n = n->rb_left;
+		} else if (cno > root->cno) {
+			n = n->rb_right;
+		} else {
+			atomic_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			return root;
+		}
 	}
+	spin_unlock(&nilfs->ns_cptree_lock);
 
-	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
-		if (nilfs_test_opt(sbi, SNAPSHOT) &&
-		    sbi->s_snapshot_cno == cno)
-			goto found; /* snapshot mount */
-	}
- out:
-	up_read(&nilfs->ns_super_sem);
 	return NULL;
-
- found:
-	atomic_inc(&sbi->s_count);
-	up_read(&nilfs->ns_super_sem);
-	return sbi;
 }
 
-int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno,
-				int snapshot_mount)
+struct nilfs_root *
+nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
 {
-	struct nilfs_sb_info *sbi;
-	int ret = 0;
+	struct rb_node **p, *parent;
+	struct nilfs_root *root, *new;
+
+	root = nilfs_lookup_root(nilfs, cno);
+	if (root)
+		return root;
+
+	new = kmalloc(sizeof(*root), GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	spin_lock(&nilfs->ns_cptree_lock);
 
-	down_read(&nilfs->ns_super_sem);
-	if (cno == 0 || cno > nilfs->ns_cno)
-		goto out_unlock;
+	p = &nilfs->ns_cptree.rb_node;
+	parent = NULL;
 
-	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
-		if (sbi->s_snapshot_cno == cno &&
-		    (!snapshot_mount || nilfs_test_opt(sbi, SNAPSHOT))) {
-					/* exclude read-only mounts */
-			ret++;
-			break;
+	while (*p) {
+		parent = *p;
+		root = rb_entry(parent, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			p = &(*p)->rb_left;
+		} else if (cno > root->cno) {
+			p = &(*p)->rb_right;
+		} else {
+			atomic_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			kfree(new);
+			return root;
 		}
 	}
-	/* for protecting recent checkpoints */
-	if (cno >= nilfs_last_cno(nilfs))
-		ret++;
 
- out_unlock:
-	up_read(&nilfs->ns_super_sem);
-	return ret;
+	new->cno = cno;
+	new->ifile = NULL;
+	new->nilfs = nilfs;
+	atomic_set(&new->count, 1);
+	atomic_set(&new->inodes_count, 0);
+	atomic_set(&new->blocks_count, 0);
+
+	rb_link_node(&new->rb_node, parent, p);
+	rb_insert_color(&new->rb_node, &nilfs->ns_cptree);
+
+	spin_unlock(&nilfs->ns_cptree_lock);
+
+	return new;
+}
+
+void nilfs_put_root(struct nilfs_root *root)
+{
+	if (atomic_dec_and_test(&root->count)) {
+		struct the_nilfs *nilfs = root->nilfs;
+
+		spin_lock(&nilfs->ns_cptree_lock);
+		rb_erase(&root->rb_node, &nilfs->ns_cptree);
+		spin_unlock(&nilfs->ns_cptree_lock);
+		if (root->ifile)
+			iput(root->ifile);
+
+		kfree(root);
+	}
 }