ext4: unify the ext4 super block loading operation

Now we load the super block from the disk in two steps. First we load
the super block with the default block size(EXT4_MIN_BLOCK_SIZE). Second
we load the super block with the real block size. The second step is a
little far from the first step. This patch move these two steps together
in a new function.
Signed-off-by: NJason Yan <yanaijie@huawei.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220916141527.1012715-15-yanaijie@huawei.comSigned-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -4920,39 +4920,21 @@ static int ext4_journal_data_mode_check(struct super_block *sb)
 	return 0;
 }
 
-static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
+static int ext4_load_super(struct super_block *sb, ext4_fsblk_t *lsb,
+			   int silent)
 {
-	struct buffer_head *bh;
-	struct ext4_super_block *es = NULL;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	struct flex_groups **flex_groups;
-	ext4_fsblk_t block;
+	struct ext4_super_block *es;
 	ext4_fsblk_t logical_sb_block;
 	unsigned long offset = 0;
-	struct inode *root;
-	int ret = -ENOMEM;
+	struct buffer_head *bh;
+	int ret = -EINVAL;
 	int blocksize;
-	unsigned int i;
-	int needs_recovery, has_huge_files;
-	int err = 0;
-	ext4_group_t first_not_zeroed;
-	struct ext4_fs_context *ctx = fc->fs_private;
-	int silent = fc->sb_flags & SB_SILENT;
-
-	/* Set defaults for the variables that will be set during parsing */
-	if (!(ctx->spec & EXT4_SPEC_JOURNAL_IOPRIO))
-		ctx->journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 
-	sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
-	sbi->s_sectors_written_start =
-		part_stat_read(sb->s_bdev, sectors[STAT_WRITE]);
-
-	/* -EINVAL is default */
-	ret = -EINVAL;
 	blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
 	if (!blocksize) {
 		ext4_msg(sb, KERN_ERR, "unable to set blocksize");
-		goto out_fail;
+		return -EINVAL;
 	}
 
 	/*
@@ -4969,8 +4951,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
 	if (IS_ERR(bh)) {
 		ext4_msg(sb, KERN_ERR, "unable to read superblock");
-		ret = PTR_ERR(bh);
-		goto out_fail;
+		return PTR_ERR(bh);
 	}
 	/*
 	 * Note: s_es must be initialized as soon as possible because
@@ -4982,9 +4963,106 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	if (sb->s_magic != EXT4_SUPER_MAGIC) {
 		if (!silent)
 			ext4_msg(sb, KERN_ERR, "VFS: Can't find ext4 filesystem");
-		goto failed_mount;
+		goto out;
 	}
 
+	if (le32_to_cpu(es->s_log_block_size) >
+	    (EXT4_MAX_BLOCK_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Invalid log block size: %u",
+			 le32_to_cpu(es->s_log_block_size));
+		goto out;
+	}
+	if (le32_to_cpu(es->s_log_cluster_size) >
+	    (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Invalid log cluster size: %u",
+			 le32_to_cpu(es->s_log_cluster_size));
+		goto out;
+	}
+
+	blocksize = EXT4_MIN_BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
+
+	/*
+	 * If the default block size is not the same as the real block size,
+	 * we need to reload it.
+	 */
+	if (sb->s_blocksize == blocksize) {
+		*lsb = logical_sb_block;
+		sbi->s_sbh = bh;
+		return 0;
+	}
+
+	/*
+	 * bh must be released before kill_bdev(), otherwise
+	 * it won't be freed and its page also. kill_bdev()
+	 * is called by sb_set_blocksize().
+	 */
+	brelse(bh);
+	/* Validate the filesystem blocksize */
+	if (!sb_set_blocksize(sb, blocksize)) {
+		ext4_msg(sb, KERN_ERR, "bad block size %d",
+				blocksize);
+		bh = NULL;
+		goto out;
+	}
+
+	logical_sb_block = sbi->s_sb_block * EXT4_MIN_BLOCK_SIZE;
+	offset = do_div(logical_sb_block, blocksize);
+	bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
+	if (IS_ERR(bh)) {
+		ext4_msg(sb, KERN_ERR, "Can't read superblock on 2nd try");
+		ret = PTR_ERR(bh);
+		bh = NULL;
+		goto out;
+	}
+	es = (struct ext4_super_block *)(bh->b_data + offset);
+	sbi->s_es = es;
+	if (es->s_magic != cpu_to_le16(EXT4_SUPER_MAGIC)) {
+		ext4_msg(sb, KERN_ERR, "Magic mismatch, very weird!");
+		goto out;
+	}
+	*lsb = logical_sb_block;
+	sbi->s_sbh = bh;
+	return 0;
+out:
+	brelse(bh);
+	return ret;
+}
+
+static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
+{
+	struct ext4_super_block *es = NULL;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct flex_groups **flex_groups;
+	ext4_fsblk_t block;
+	ext4_fsblk_t logical_sb_block;
+	struct inode *root;
+	int ret = -ENOMEM;
+	int blocksize;
+	unsigned int i;
+	int needs_recovery, has_huge_files;
+	int err = 0;
+	ext4_group_t first_not_zeroed;
+	struct ext4_fs_context *ctx = fc->fs_private;
+	int silent = fc->sb_flags & SB_SILENT;
+
+	/* Set defaults for the variables that will be set during parsing */
+	if (!(ctx->spec & EXT4_SPEC_JOURNAL_IOPRIO))
+		ctx->journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
+
+	sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
+	sbi->s_sectors_written_start =
+		part_stat_read(sb->s_bdev, sectors[STAT_WRITE]);
+
+	/* -EINVAL is default */
+	ret = -EINVAL;
+	err = ext4_load_super(sb, &logical_sb_block, silent);
+	if (err)
+		goto out_fail;
+
+	es = sbi->s_es;
+	blocksize = sb->s_blocksize;
 	sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);
 
 	err = ext4_init_metadata_csum(sb, es);
@@ -5005,23 +5083,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	 */
 	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;
 
-	if (le32_to_cpu(es->s_log_block_size) >
-	    (EXT4_MAX_BLOCK_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
-		ext4_msg(sb, KERN_ERR,
-			 "Invalid log block size: %u",
-			 le32_to_cpu(es->s_log_block_size));
-		goto failed_mount;
-	}
-	if (le32_to_cpu(es->s_log_cluster_size) >
-	    (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
-		ext4_msg(sb, KERN_ERR,
-			 "Invalid log cluster size: %u",
-			 le32_to_cpu(es->s_log_cluster_size));
-		goto failed_mount;
-	}
-
-	blocksize = EXT4_MIN_BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
-
 	if (blocksize == PAGE_SIZE)
 		set_opt(sb, DIOREAD_NOLOCK);
 
@@ -5088,40 +5149,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 		goto failed_mount;
 	}
 
-	if (sb->s_blocksize != blocksize) {
-		/*
-		 * bh must be released before kill_bdev(), otherwise
-		 * it won't be freed and its page also. kill_bdev()
-		 * is called by sb_set_blocksize().
-		 */
-		brelse(bh);
-		/* Validate the filesystem blocksize */
-		if (!sb_set_blocksize(sb, blocksize)) {
-			ext4_msg(sb, KERN_ERR, "bad block size %d",
-					blocksize);
-			bh = NULL;
-			goto failed_mount;
-		}
-
-		logical_sb_block = sbi->s_sb_block * EXT4_MIN_BLOCK_SIZE;
-		offset = do_div(logical_sb_block, blocksize);
-		bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
-		if (IS_ERR(bh)) {
-			ext4_msg(sb, KERN_ERR,
-			       "Can't read superblock on 2nd try");
-			ret = PTR_ERR(bh);
-			bh = NULL;
-			goto failed_mount;
-		}
-		es = (struct ext4_super_block *)(bh->b_data + offset);
-		sbi->s_es = es;
-		if (es->s_magic != cpu_to_le16(EXT4_SUPER_MAGIC)) {
-			ext4_msg(sb, KERN_ERR,
-			       "Magic mismatch, very weird!");
-			goto failed_mount;
-		}
-	}
-
 	has_huge_files = ext4_has_feature_huge_file(sb);
 	sbi->s_bitmap_maxbytes = ext4_max_bitmap_size(sb->s_blocksize_bits,
 						      has_huge_files);
@@ -5158,7 +5185,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	sbi->s_itb_per_group = sbi->s_inodes_per_group /
 					sbi->s_inodes_per_block;
 	sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
-	sbi->s_sbh = bh;
 	sbi->s_mount_state = le16_to_cpu(es->s_state) & ~EXT4_FC_REPLAY;
 	sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb));
 	sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));
@@ -5595,7 +5621,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 #endif
 	fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
 	/* ext4_blkdev_remove() calls kill_bdev(), release bh before it. */
-	brelse(bh);
+	brelse(sbi->s_sbh);
 	ext4_blkdev_remove(sbi);
 out_fail:
 	sb->s_fs_info = NULL;