nilfs2: use root object to get ifile

This rewrites functions using ifile so that they get ifile from
nilfs_root object, and will remove sbi->s_ifile.  Some functions that
don't know the root object are extended to receive it from caller.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

7 files changed, 67 insertions, 80 deletions

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 7306fc7c4962..7e883d5a5033 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -301,7 +301,7 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
         ii->i_state = 1 << NILFS_I_NEW;
         ii->i_root = root;
 
-        err = nilfs_ifile_create_inode(sbi->s_ifile, &ino, &ii->i_bh);
+        err = nilfs_ifile_create_inode(root->ifile, &ino, &ii->i_bh);
         if (unlikely(err))
                 goto failed_ifile_create_inode;
         /* reference count of i_bh inherits from nilfs_mdt_read_block() */
@@ -358,16 +358,6 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
         return ERR_PTR(err);
 }
 
-void nilfs_free_inode(struct inode *inode)
-{
-        struct super_block *sb = inode->i_sb;
-        struct nilfs_sb_info *sbi = NILFS_SB(sb);
-
-        /* XXX: check error code? Is there any thing I can do? */
-        (void) nilfs_ifile_delete_inode(sbi->s_ifile, inode->i_ino);
-        atomic_dec(&sbi->s_inodes_count);
-}
-
 void nilfs_set_inode_flags(struct inode *inode)
 {
         unsigned int flags = NILFS_I(inode)->i_flags;
@@ -431,7 +421,8 @@ int nilfs_read_inode_common(struct inode *inode,
         return 0;
 }
 
-static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
+static int __nilfs_read_inode(struct super_block *sb,
+                              struct nilfs_root *root, unsigned long ino,
                               struct inode *inode)
 {
         struct nilfs_sb_info *sbi = NILFS_SB(sb);
@@ -441,11 +432,11 @@ static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
         int err;
 
         down_read(&NILFS_MDT(dat)->mi_sem);     /* XXX */
-        err = nilfs_ifile_get_inode_block(sbi->s_ifile, ino, &bh);
+        err = nilfs_ifile_get_inode_block(root->ifile, ino, &bh);
         if (unlikely(err))
                 goto bad_inode;
 
-        raw_inode = nilfs_ifile_map_inode(sbi->s_ifile, ino, bh);
+        raw_inode = nilfs_ifile_map_inode(root->ifile, ino, bh);
 
         err = nilfs_read_inode_common(inode, raw_inode);
         if (err)
@@ -468,14 +459,14 @@ static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
                         inode, inode->i_mode,
                         huge_decode_dev(le64_to_cpu(raw_inode->i_device_code)));
         }
-        nilfs_ifile_unmap_inode(sbi->s_ifile, ino, bh);
+        nilfs_ifile_unmap_inode(root->ifile, ino, bh);
         brelse(bh);
         up_read(&NILFS_MDT(dat)->mi_sem);       /* XXX */
         nilfs_set_inode_flags(inode);
         return 0;
 
  failed_unmap:
-        nilfs_ifile_unmap_inode(sbi->s_ifile, ino, bh);
+        nilfs_ifile_unmap_inode(root->ifile, ino, bh);
         brelse(bh);
 
  bad_inode:
@@ -530,7 +521,7 @@ struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
         if (!(inode->i_state & I_NEW))
                 return inode;
 
-        err = __nilfs_read_inode(sb, ino, inode);
+        err = __nilfs_read_inode(sb, root, ino, inode);
         if (unlikely(err)) {
                 iget_failed(inode);
                 return ERR_PTR(err);
@@ -595,21 +586,20 @@ void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
 {
         ino_t ino = inode->i_ino;
         struct nilfs_inode_info *ii = NILFS_I(inode);
-        struct super_block *sb = inode->i_sb;
-        struct nilfs_sb_info *sbi = NILFS_SB(sb);
+        struct inode *ifile = ii->i_root->ifile;
         struct nilfs_inode *raw_inode;
 
-        raw_inode = nilfs_ifile_map_inode(sbi->s_ifile, ino, ibh);
+        raw_inode = nilfs_ifile_map_inode(ifile, ino, ibh);
 
         if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
-                memset(raw_inode, 0, NILFS_MDT(sbi->s_ifile)->mi_entry_size);
+                memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
         set_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
 
         nilfs_write_inode_common(inode, raw_inode, 0);
                 /* XXX: call with has_bmap = 0 is a workaround to avoid
                    deadlock of bmap. This delays update of i_bmap to just
                    before writing */
-        nilfs_ifile_unmap_inode(sbi->s_ifile, ino, ibh);
+        nilfs_ifile_unmap_inode(ifile, ino, ibh);
 }
 
 #define NILFS_MAX_TRUNCATE_BLOCKS       16384  /* 64MB for 4KB block */
@@ -719,12 +709,16 @@ void nilfs_evict_inode(struct inode *inode)
         if (inode->i_data.nrpages)
                 truncate_inode_pages(&inode->i_data, 0);
 
+        /* TODO: some of the following operations may fail.  */
         nilfs_truncate_bmap(ii, 0);
         nilfs_mark_inode_dirty(inode);
         end_writeback(inode);
+
+        nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
+        atomic_dec(&NILFS_SB(sb)->s_inodes_count);
+
         nilfs_clear_inode(inode);
-        nilfs_free_inode(inode);
-        /* nilfs_free_inode() marks inode buffer dirty */
+
         if (IS_SYNC(inode))
                 nilfs_set_transaction_flag(NILFS_TI_SYNC);
         nilfs_transaction_commit(sb);
@@ -779,8 +773,8 @@ int nilfs_load_inode_block(struct nilfs_sb_info *sbi, struct inode *inode,
         spin_lock(&sbi->s_inode_lock);
         if (ii->i_bh == NULL) {
                 spin_unlock(&sbi->s_inode_lock);
-                err = nilfs_ifile_get_inode_block(sbi->s_ifile, inode->i_ino,
-                                                  pbh);
+                err = nilfs_ifile_get_inode_block(ii->i_root->ifile,
+                                                  inode->i_ino, pbh);
                 if (unlikely(err))
                         return err;
                 spin_lock(&sbi->s_inode_lock);
@@ -860,7 +854,7 @@ int nilfs_mark_inode_dirty(struct inode *inode)
         }
         nilfs_update_inode(inode, ibh);
         nilfs_mdt_mark_buffer_dirty(ibh);
-        nilfs_mdt_mark_dirty(sbi->s_ifile);
+        nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
         brelse(ibh);
         return 0;
 }
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index aa7940f7ecf1..3870c109aba3 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -286,7 +286,6 @@ extern int nilfs_commit_super(struct nilfs_sb_info *, int);
 extern int nilfs_cleanup_super(struct nilfs_sb_info *);
 int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
                             struct nilfs_root **root);
-extern void nilfs_detach_checkpoint(struct nilfs_sb_info *);
 
 /* gcinode.c */
 int nilfs_gccache_submit_read_data(struct inode *, sector_t, sector_t, __u64,
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index a9a5ba8f57d5..dcb5a9812c6c 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -773,7 +773,7 @@ int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,
                         goto failed;
                 }
 
-                err = nilfs_attach_segment_constructor(sbi);
+                err = nilfs_attach_segment_constructor(sbi, root);
                 if (unlikely(err))
                         goto failed;
 
@@ -791,7 +791,6 @@ int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,
         }
 
  failed:
-        nilfs_detach_checkpoint(sbi);
         nilfs_put_root(root);
         return err;
 }
diff --git a/fs/nilfs2/sb.h b/fs/nilfs2/sb.h
index 0776ccc2504a..50c418e6438e 100644
--- a/fs/nilfs2/sb.h
+++ b/fs/nilfs2/sb.h
@@ -68,9 +68,6 @@ struct nilfs_sb_info {
         spinlock_t s_inode_lock;        /* Lock for the nilfs inode.
                                            It covers s_dirty_files list */
 
-        /* Metadata files */
-        struct inode *s_ifile;          /* index file inode */
-
         /* Inode allocator */
         spinlock_t s_next_gen_lock;
         u32 s_next_generation;
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 9cf71389f369..2a6b74e6699d 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -763,12 +763,12 @@ static void nilfs_dispose_list(struct nilfs_sb_info *sbi,
         }
 }
 
-static int nilfs_test_metadata_dirty(struct nilfs_sb_info *sbi)
+static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
+                                     struct nilfs_root *root)
 {
-        struct the_nilfs *nilfs = sbi->s_nilfs;
         int ret = 0;
 
-        if (nilfs_mdt_fetch_dirty(sbi->s_ifile))
+        if (nilfs_mdt_fetch_dirty(root->ifile))
                 ret++;
         if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
                 ret++;
@@ -793,7 +793,7 @@ static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
         struct nilfs_sb_info *sbi = sci->sc_sbi;
         int ret = 0;
 
-        if (nilfs_test_metadata_dirty(sbi))
+        if (nilfs_test_metadata_dirty(sbi->s_nilfs, sci->sc_root))
                 set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
         spin_lock(&sbi->s_inode_lock);
@@ -809,7 +809,7 @@ static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
         struct nilfs_sb_info *sbi = sci->sc_sbi;
         struct the_nilfs *nilfs = sbi->s_nilfs;
 
-        nilfs_mdt_clear_dirty(sbi->s_ifile);
+        nilfs_mdt_clear_dirty(sci->sc_root->ifile);
         nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
         nilfs_mdt_clear_dirty(nilfs->ns_sufile);
         nilfs_mdt_clear_dirty(nilfs_dat_inode(nilfs));
@@ -869,7 +869,8 @@ static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
         else
                 nilfs_checkpoint_set_minor(raw_cp);
 
-        nilfs_write_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode, 1);
+        nilfs_write_inode_common(sci->sc_root->ifile,
+                                 &raw_cp->cp_ifile_inode, 1);
         nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
         return 0;
 
@@ -894,13 +895,12 @@ static void nilfs_fill_in_file_bmap(struct inode *ifile,
         }
 }
 
-static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci,
-                                            struct inode *ifile)
+static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)
 {
         struct nilfs_inode_info *ii;
 
         list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {
-                nilfs_fill_in_file_bmap(ifile, ii);
+                nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);
                 set_bit(NILFS_I_COLLECTED, &ii->i_state);
         }
 }
@@ -1143,7 +1143,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
                 sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
                 /* Fall through */
         case NILFS_ST_IFILE:
-                err = nilfs_segctor_scan_file(sci, sbi->s_ifile,
+                err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,
                                               &nilfs_sc_file_ops);
                 if (unlikely(err))
                         break;
@@ -1984,6 +1984,7 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
                                         struct nilfs_sb_info *sbi)
 {
         struct nilfs_inode_info *ii, *n;
+        struct inode *ifile = sci->sc_root->ifile;
 
         spin_lock(&sbi->s_inode_lock);
  retry:
@@ -1994,14 +1995,14 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
 
                         spin_unlock(&sbi->s_inode_lock);
                         err = nilfs_ifile_get_inode_block(
-                                sbi->s_ifile, ii->vfs_inode.i_ino, &ibh);
+                                ifile, ii->vfs_inode.i_ino, &ibh);
                         if (unlikely(err)) {
                                 nilfs_warning(sbi->s_super, __func__,
                                               "failed to get inode block.\n");
                                 return err;
                         }
                         nilfs_mdt_mark_buffer_dirty(ibh);
-                        nilfs_mdt_mark_dirty(sbi->s_ifile);
+                        nilfs_mdt_mark_dirty(ifile);
                         spin_lock(&sbi->s_inode_lock);
                         if (likely(!ii->i_bh))
                                 ii->i_bh = ibh;
@@ -2058,7 +2059,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
         if (unlikely(err))
                 goto out;
 
-        if (nilfs_test_metadata_dirty(sbi))
+        if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
                 set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
         if (nilfs_segctor_clean(sci))
@@ -2090,7 +2091,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
                         goto failed;
 
                 if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
-                        nilfs_segctor_fill_in_file_bmap(sci, sbi->s_ifile);
+                        nilfs_segctor_fill_in_file_bmap(sci);
 
                 if (mode == SC_LSEG_SR &&
                     sci->sc_stage.scnt >= NILFS_ST_CPFILE) {
@@ -2684,7 +2685,8 @@ static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
 /*
  * Setup & clean-up functions
  */
-static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi)
+static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi,
+                                               struct nilfs_root *root)
 {
         struct nilfs_sc_info *sci;
 
@@ -2695,6 +2697,9 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi)
         sci->sc_sbi = sbi;
         sci->sc_super = sbi->s_super;
 
+        nilfs_get_root(root);
+        sci->sc_root = root;
+
         init_waitqueue_head(&sci->sc_wait_request);
         init_waitqueue_head(&sci->sc_wait_daemon);
         init_waitqueue_head(&sci->sc_wait_task);
@@ -2769,6 +2774,8 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
         WARN_ON(!list_empty(&sci->sc_segbufs));
         WARN_ON(!list_empty(&sci->sc_write_logs));
 
+        nilfs_put_root(sci->sc_root);
+
         down_write(&sbi->s_nilfs->ns_segctor_sem);
 
         del_timer_sync(&sci->sc_timer);
@@ -2778,6 +2785,7 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
 /**
  * nilfs_attach_segment_constructor - attach a segment constructor
  * @sbi: nilfs_sb_info
+ * @root: root object of the current filesystem tree
  *
  * nilfs_attach_segment_constructor() allocates a struct nilfs_sc_info,
  * initializes it, and starts the segment constructor.
@@ -2787,7 +2795,8 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
  *
  * %-ENOMEM - Insufficient memory available.
  */
-int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
+int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
+                                     struct nilfs_root *root)
 {
         struct the_nilfs *nilfs = sbi->s_nilfs;
         int err;
@@ -2801,7 +2810,7 @@ int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
                 nilfs_detach_segment_constructor(sbi);
         }
 
-        sbi->s_sc_info = nilfs_segctor_new(sbi);
+        sbi->s_sc_info = nilfs_segctor_new(sbi, root);
         if (!sbi->s_sc_info)
                 return -ENOMEM;
 
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
index 675d932148a4..cd8056e7cbed 100644
--- a/fs/nilfs2/segment.h
+++ b/fs/nilfs2/segment.h
@@ -29,6 +29,8 @@
 #include <linux/nilfs2_fs.h>
 #include "sb.h"
 
+struct nilfs_root;
+
 /**
  * struct nilfs_recovery_info - Recovery information
  * @ri_need_recovery: Recovery status
@@ -87,6 +89,7 @@ struct nilfs_segsum_pointer {
  * struct nilfs_sc_info - Segment constructor information
  * @sc_super: Back pointer to super_block struct
  * @sc_sbi: Back pointer to nilfs_sb_info struct
+ * @sc_root: root object of the current filesystem tree
  * @sc_nblk_inc: Block count of current generation
  * @sc_dirty_files: List of files to be written
  * @sc_gc_inodes: List of GC inodes having blocks to be written
@@ -129,6 +132,7 @@ struct nilfs_segsum_pointer {
 struct nilfs_sc_info {
         struct super_block     *sc_super;
         struct nilfs_sb_info   *sc_sbi;
+        struct nilfs_root      *sc_root;
 
         unsigned long           sc_nblk_inc;
 
@@ -231,7 +235,8 @@ extern void nilfs_flush_segment(struct super_block *, ino_t);
 extern int nilfs_clean_segments(struct super_block *, struct nilfs_argv *,
                                 void **);
 
-extern int nilfs_attach_segment_constructor(struct nilfs_sb_info *);
+int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
+                                     struct nilfs_root *root);
 extern void nilfs_detach_segment_constructor(struct nilfs_sb_info *);
 
 /* recovery.c */
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index adbf5826b837..87c57810ae88 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -358,9 +358,9 @@ static void nilfs_put_super(struct super_block *sb)
         down_write(&nilfs->ns_super_sem);
         if (nilfs->ns_current == sbi)
                 nilfs->ns_current = NULL;
+        list_del_init(&sbi->s_list);
         up_write(&nilfs->ns_super_sem);
 
-        nilfs_detach_checkpoint(sbi);
         put_nilfs(sbi->s_nilfs);
         sbi->s_super = NULL;
         sb->s_fs_info = NULL;
@@ -405,13 +405,12 @@ int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
         if (!root)
                 return err;
 
-        down_write(&nilfs->ns_super_sem);
-        list_add(&sbi->s_list, &nilfs->ns_supers);
-        up_write(&nilfs->ns_super_sem);
+        if (root->ifile)
+                goto reuse; /* already attached checkpoint */
 
-        sbi->s_ifile = nilfs_ifile_new(sbi, nilfs->ns_inode_size);
-        if (!sbi->s_ifile)
-                goto delist;
+        root->ifile = nilfs_ifile_new(sbi, nilfs->ns_inode_size);
+        if (!root->ifile)
+                goto failed;
 
         down_read(&nilfs->ns_segctor_sem);
         err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
@@ -427,7 +426,7 @@ int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
                 }
                 goto failed;
         }
-        err = nilfs_read_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode);
+        err = nilfs_read_inode_common(root->ifile, &raw_cp->cp_ifile_inode);
         if (unlikely(err))
                 goto failed_bh;
         atomic_set(&sbi->s_inodes_count, le64_to_cpu(raw_cp->cp_inodes_count));
@@ -435,35 +434,18 @@ int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
 
         nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
 
+ reuse:
         *rootp = root;
         return 0;
 
  failed_bh:
         nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
  failed:
-        nilfs_mdt_destroy(sbi->s_ifile);
-        sbi->s_ifile = NULL;
-
- delist:
-        down_write(&nilfs->ns_super_sem);
-        list_del_init(&sbi->s_list);
-        up_write(&nilfs->ns_super_sem);
         nilfs_put_root(root);
 
         return err;
 }
 
-void nilfs_detach_checkpoint(struct nilfs_sb_info *sbi)
-{
-        struct the_nilfs *nilfs = sbi->s_nilfs;
-
-        nilfs_mdt_destroy(sbi->s_ifile);
-        sbi->s_ifile = NULL;
-        down_write(&nilfs->ns_super_sem);
-        list_del_init(&sbi->s_list);
-        up_write(&nilfs->ns_super_sem);
-}
-
 static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
         struct super_block *sb = dentry->d_sb;
@@ -862,7 +844,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
         }
 
         if (!(sb->s_flags & MS_RDONLY)) {
-                err = nilfs_attach_segment_constructor(sbi);
+                err = nilfs_attach_segment_constructor(sbi, fsroot);
                 if (err)
                         goto failed_checkpoint;
         }
@@ -896,6 +878,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
         }
 
         down_write(&nilfs->ns_super_sem);
+        list_add(&sbi->s_list, &nilfs->ns_supers);
         if (!nilfs_test_opt(sbi, SNAPSHOT))
                 nilfs->ns_current = sbi;
         up_write(&nilfs->ns_super_sem);
@@ -906,7 +889,6 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
         nilfs_detach_segment_constructor(sbi);
 
  failed_checkpoint:
-        nilfs_detach_checkpoint(sbi);
         nilfs_put_root(fsroot);
 
  failed_sbi:
@@ -966,6 +948,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
                 up_write(&nilfs->ns_sem);
         } else {
                 __u64 features;
+                struct nilfs_root *root;
 
                 /*
                  * Mounting a RDONLY partition read-write, so reread and
@@ -987,7 +970,8 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
 
                 sb->s_flags &= ~MS_RDONLY;
 
-                err = nilfs_attach_segment_constructor(sbi);
+                root = NILFS_I(sb->s_root->d_inode)->i_root;
+                err = nilfs_attach_segment_constructor(sbi, root);
                 if (err)
                         goto restore_opts;