nilfs2: add routine to move secondary super block

After resizing the filesystem, the secondary super block must be moved
to a new location.  This adds a helper function for this.

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

1 files changed, 57 insertions, 0 deletions

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 062cca065195..eba5b53b1080 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -347,6 +347,63 @@ int nilfs_cleanup_super(struct super_block *sb)
         return ret;
 }
 
+/**
+ * nilfs_move_2nd_super - relocate secondary super block
+ * @sb: super block instance
+ * @sb2off: new offset of the secondary super block (in bytes)
+ */
+static int nilfs_move_2nd_super(struct super_block *sb, loff_t sb2off)
+{
+        struct the_nilfs *nilfs = sb->s_fs_info;
+        struct buffer_head *nsbh;
+        struct nilfs_super_block *nsbp;
+        sector_t blocknr, newblocknr;
+        unsigned long offset;
+        int sb2i = -1;  /* array index of the secondary superblock */
+        int ret = 0;
+
+        /* nilfs->ns_sem must be locked by the caller. */
+        if (nilfs->ns_sbh[1] &&
+            nilfs->ns_sbh[1]->b_blocknr > nilfs->ns_first_data_block) {
+                sb2i = 1;
+                blocknr = nilfs->ns_sbh[1]->b_blocknr;
+        } else if (nilfs->ns_sbh[0]->b_blocknr > nilfs->ns_first_data_block) {
+                sb2i = 0;
+                blocknr = nilfs->ns_sbh[0]->b_blocknr;
+        }
+        if (sb2i >= 0 && (u64)blocknr << nilfs->ns_blocksize_bits == sb2off)
+                goto out;  /* super block location is unchanged */
+
+        /* Get new super block buffer */
+        newblocknr = sb2off >> nilfs->ns_blocksize_bits;
+        offset = sb2off & (nilfs->ns_blocksize - 1);
+        nsbh = sb_getblk(sb, newblocknr);
+        if (!nsbh) {
+                printk(KERN_WARNING
+                       "NILFS warning: unable to move secondary superblock "
+                       "to block %llu\n", (unsigned long long)newblocknr);
+                ret = -EIO;
+                goto out;
+        }
+        nsbp = (void *)nsbh->b_data + offset;
+        memset(nsbp, 0, nilfs->ns_blocksize);
+
+        if (sb2i >= 0) {
+                memcpy(nsbp, nilfs->ns_sbp[sb2i], nilfs->ns_sbsize);
+                brelse(nilfs->ns_sbh[sb2i]);
+                nilfs->ns_sbh[sb2i] = nsbh;
+                nilfs->ns_sbp[sb2i] = nsbp;
+        } else if (nilfs->ns_sbh[0]->b_blocknr < nilfs->ns_first_data_block) {
+                /* secondary super block will be restored to index 1 */
+                nilfs->ns_sbh[1] = nsbh;
+                nilfs->ns_sbp[1] = nsbp;
+        } else {
+                brelse(nsbh);
+        }
+out:
+        return ret;
+}
+
 static void nilfs_put_super(struct super_block *sb)
 {
         struct the_nilfs *nilfs = sb->s_fs_info;