ext4: read-only support for bigalloc file systems

This adds supports for bigalloc file systems.  It teaches the mount
code just enough about bigalloc superblock fields that it will mount
the file system without freaking out that the number of blocks per
group is too big.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 50 insertions, 8 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 5dcd0dacc59..823e7d9deee 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1953,7 +1953,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 		res = MS_RDONLY;
 	}
 	if (read_only)
-		return res;
+		goto done;
 	if (!(sbi->s_mount_state & EXT4_VALID_FS))
 		ext4_msg(sb, KERN_WARNING, "warning: mounting unchecked fs, "
 			 "running e2fsck is recommended");
@@ -1984,6 +1984,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 		EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
 
 	ext4_commit_super(sb, 1);
+done:
 	if (test_opt(sb, DEBUG))
 		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
 				"bpg=%lu, ipg=%lu, mo=%04x, mo2=%04x]\n",
@@ -3105,10 +3106,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	char *cp;
 	const char *descr;
 	int ret = -ENOMEM;
-	int blocksize;
+	int blocksize, clustersize;
 	unsigned int db_count;
 	unsigned int i;
-	int needs_recovery, has_huge_files;
+	int needs_recovery, has_huge_files, has_bigalloc;
 	__u64 blocks_count;
 	int err;
 	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
@@ -3412,12 +3413,53 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		sb->s_dirt = 1;
 	}
 
-	if (sbi->s_blocks_per_group > blocksize * 8) {
-		ext4_msg(sb, KERN_ERR,
-		       "#blocks per group too big: %lu",
-		       sbi->s_blocks_per_group);
-		goto failed_mount;
+	/* Handle clustersize */
+	clustersize = BLOCK_SIZE << le32_to_cpu(es->s_log_cluster_size);
+	has_bigalloc = EXT4_HAS_RO_COMPAT_FEATURE(sb,
+				EXT4_FEATURE_RO_COMPAT_BIGALLOC);
+	if (has_bigalloc) {
+		if (clustersize < blocksize) {
+			ext4_msg(sb, KERN_ERR,
+				 "cluster size (%d) smaller than "
+				 "block size (%d)", clustersize, blocksize);
+			goto failed_mount;
+		}
+		sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
+			le32_to_cpu(es->s_log_block_size);
+		sbi->s_clusters_per_group =
+			le32_to_cpu(es->s_clusters_per_group);
+		if (sbi->s_clusters_per_group > blocksize * 8) {
+			ext4_msg(sb, KERN_ERR,
+				 "#clusters per group too big: %lu",
+				 sbi->s_clusters_per_group);
+			goto failed_mount;
+		}
+		if (sbi->s_blocks_per_group !=
+		    (sbi->s_clusters_per_group * (clustersize / blocksize))) {
+			ext4_msg(sb, KERN_ERR, "blocks per group (%lu) and "
+				 "clusters per group (%lu) inconsistent",
+				 sbi->s_blocks_per_group,
+				 sbi->s_clusters_per_group);
+			goto failed_mount;
+		}
+	} else {
+		if (clustersize != blocksize) {
+			ext4_warning(sb, "fragment/cluster size (%d) != "
+				     "block size (%d)", clustersize,
+				     blocksize);
+			clustersize = blocksize;
+		}
+		if (sbi->s_blocks_per_group > blocksize * 8) {
+			ext4_msg(sb, KERN_ERR,
+				 "#blocks per group too big: %lu",
+				 sbi->s_blocks_per_group);
+			goto failed_mount;
+		}
+		sbi->s_clusters_per_group = sbi->s_blocks_per_group;
+		sbi->s_cluster_bits = 0;
 	}
+	sbi->s_cluster_ratio = clustersize / blocksize;
+
 	if (sbi->s_inodes_per_group > blocksize * 8) {
 		ext4_msg(sb, KERN_ERR,
 		       "#inodes per group too big: %lu",