nilfs2: do not allocate multiple super block instances for a device

This stops allocating multiple super block instances for a device.

All snapshots and a current mode mount (i.e. latest tree) will be
controlled with nilfs_root objects that are kept within an sb
instance.

nilfs_get_sb() is rewritten so that it always has a root object for
the latest tree and snapshots make additional root objects.

The root dentry of the latest tree is binded to sb->s_root even if it
isn't attached on a directory.  Root dentries of snapshots or the
latest tree are binded to mnt->mnt_root on which they are mounted.

With this patch, nilfs_find_sbinfo() function, nilfs->ns_supers list,
and nilfs->ns_current back pointer, are deleted.  In addition,
init_nilfs() and load_nilfs() are simplified since they will be called
once for a device, not repeatedly called for mount points.

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

1 files changed, 1 insertions, 88 deletions

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 89c78562d0e9..960c28797bb2 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -82,11 +82,9 @@ static struct the_nilfs *alloc_nilfs(struct block_device *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_cptree = RB_ROOT;
@@ -307,15 +305,6 @@ 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) {
@@ -632,12 +621,7 @@ 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.
@@ -651,27 +635,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
         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;
-
-                err = nilfs_check_feature_compatibility(sb, sbp);
-                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, NILFS_MIN_BLOCK_SIZE);
         if (!blocksize) {
@@ -901,56 +864,6 @@ void nilfs_put_root(struct nilfs_root *root)
         }
 }
 
-/**
- * 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_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;
-        }
-
-        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)
 {