+
+static void end_bio_io_page(struct bio *bio, int error)
+{
+ struct page *page = bio->bi_private;
+
+ if (!error)
+ SetPageUptodate(page);
+ else
+ printk(KERN_WARNING "gfs2: error %d reading superblock\n", error);
+ unlock_page(page);
+}
+
+static void gfs2_sb_in(struct gfs2_sb_host *sb, const void *buf)
+{
+ const struct gfs2_sb *str = buf;
+
+ sb->sb_magic = be32_to_cpu(str->sb_header.mh_magic);
+ sb->sb_type = be32_to_cpu(str->sb_header.mh_type);
+ sb->sb_format = be32_to_cpu(str->sb_header.mh_format);
+ sb->sb_fs_format = be32_to_cpu(str->sb_fs_format);
+ sb->sb_multihost_format = be32_to_cpu(str->sb_multihost_format);
+ sb->sb_bsize = be32_to_cpu(str->sb_bsize);
+ sb->sb_bsize_shift = be32_to_cpu(str->sb_bsize_shift);
+ sb->sb_master_dir.no_addr = be64_to_cpu(str->sb_master_dir.no_addr);
+ sb->sb_master_dir.no_formal_ino = be64_to_cpu(str->sb_master_dir.no_formal_ino);
+ sb->sb_root_dir.no_addr = be64_to_cpu(str->sb_root_dir.no_addr);
+ sb->sb_root_dir.no_formal_ino = be64_to_cpu(str->sb_root_dir.no_formal_ino);
+
+ memcpy(sb->sb_lockproto, str->sb_lockproto, GFS2_LOCKNAME_LEN);
+ memcpy(sb->sb_locktable, str->sb_locktable, GFS2_LOCKNAME_LEN);
+}
+
+/**
+ * gfs2_read_super - Read the gfs2 super block from disk
+ * @sdp: The GFS2 super block
+ * @sector: The location of the super block
+ * @error: The error code to return
+ *
+ * This uses the bio functions to read the super block from disk
+ * because we want to be 100% sure that we never read cached data.
+ * A super block is read twice only during each GFS2 mount and is
+ * never written to by the filesystem. The first time its read no
+ * locks are held, and the only details which are looked at are those
+ * relating to the locking protocol. Once locking is up and working,
+ * the sb is read again under the lock to establish the location of
+ * the master directory (contains pointers to journals etc) and the
+ * root directory.
+ *
+ * Returns: 0 on success or error
+ */
+
+int gfs2_read_super(struct gfs2_sbd *sdp, sector_t sector)
+{
+ struct super_block *sb = sdp->sd_vfs;
+ struct gfs2_sb *p;
+ struct page *page;
+ struct bio *bio;
+
+ page = alloc_page(GFP_KERNEL);
+ if (unlikely(!page))
+ return -ENOBUFS;
+
+ ClearPageUptodate(page);
+ ClearPageDirty(page);
+ lock_page(page);
+
+ bio = bio_alloc(GFP_KERNEL, 1);
+ if (unlikely(!bio)) {
+ __free_page(page);
+ return -ENOBUFS;
+ }
+
+ bio->bi_sector = sector * (sb->s_blocksize >> 9);
+ bio->bi_bdev = sb->s_bdev;
+ bio_add_page(bio, page, PAGE_SIZE, 0);
+
+ bio->bi_end_io = end_bio_io_page;
+ bio->bi_private = page;
+ submit_bio(READ_SYNC | (1 << BIO_RW_META), bio);
+ wait_on_page_locked(page);
+ bio_put(bio);
+ if (!PageUptodate(page)) {
+ __free_page(page);
+ return -EIO;
+ }
+ p = kmap(page);
+ gfs2_sb_in(&sdp->sd_sb, p);
+ kunmap(page);
+ __free_page(page);
+ return 0;
+}
+