ext2: Drop fragment support

Ext2 has fields in superblock reserved for subblock allocation support.
However that never landed. Drop the many years dead code.

Reported-by: syzbot+af5e10f73dbff48f70af@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>

Author: jankara

fs/ext2/ext2.h

@@ -70,10 +70,7 @@ struct mb_cache;
  * second extended-fs super-block data in memory
  */
 struct ext2_sb_info {
-	unsigned long s_frag_size;	/* Size of a fragment in bytes */
-	unsigned long s_frags_per_block;/* Number of fragments per block */
 	unsigned long s_inodes_per_block;/* Number of inodes per block */
-	unsigned long s_frags_per_group;/* Number of fragments in a group */
 	unsigned long s_blocks_per_group;/* Number of blocks in a group */
 	unsigned long s_inodes_per_group;/* Number of inodes in a group */
 	unsigned long s_itb_per_group;	/* Number of inode table blocks per group */
@@ -188,15 +185,6 @@ static inline struct ext2_sb_info *EXT2_SB(struct super_block *sb)
 #define EXT2_INODE_SIZE(s)		(EXT2_SB(s)->s_inode_size)
 #define EXT2_FIRST_INO(s)		(EXT2_SB(s)->s_first_ino)
 
-/*
- * Macro-instructions used to manage fragments
- */
-#define EXT2_MIN_FRAG_SIZE		1024
-#define	EXT2_MAX_FRAG_SIZE		4096
-#define EXT2_MIN_FRAG_LOG_SIZE		  10
-#define EXT2_FRAG_SIZE(s)		(EXT2_SB(s)->s_frag_size)
-#define EXT2_FRAGS_PER_BLOCK(s)		(EXT2_SB(s)->s_frags_per_block)
-
 /*
  * Structure of a blocks group descriptor
  */

fs/ext2/super.c

@@ -668,10 +668,9 @@ static int ext2_setup_super (struct super_block * sb,
 		es->s_max_mnt_count = cpu_to_le16(EXT2_DFL_MAX_MNT_COUNT);
 	le16_add_cpu(&es->s_mnt_count, 1);
 	if (test_opt (sb, DEBUG))
-		ext2_msg(sb, KERN_INFO, "%s, %s, bs=%lu, fs=%lu, gc=%lu, "
+		ext2_msg(sb, KERN_INFO, "%s, %s, bs=%lu, gc=%lu, "
 			"bpg=%lu, ipg=%lu, mo=%04lx]",
 			EXT2FS_VERSION, EXT2FS_DATE, sb->s_blocksize,
-			sbi->s_frag_size,
 			sbi->s_groups_count,
 			EXT2_BLOCKS_PER_GROUP(sb),
 			EXT2_INODES_PER_GROUP(sb),
@@ -1012,14 +1011,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 		}
 	}
 
-	sbi->s_frag_size = EXT2_MIN_FRAG_SIZE <<
-				   le32_to_cpu(es->s_log_frag_size);
-	if (sbi->s_frag_size == 0)
-		goto cantfind_ext2;
-	sbi->s_frags_per_block = sb->s_blocksize / sbi->s_frag_size;
-
 	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
-	sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
 	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
 
 	sbi->s_inodes_per_block = sb->s_blocksize / EXT2_INODE_SIZE(sb);
@@ -1045,11 +1037,10 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 	}
 
-	if (sb->s_blocksize != sbi->s_frag_size) {
+	if (es->s_log_frag_size != es->s_log_block_size) {
 		ext2_msg(sb, KERN_ERR,
-			"error: fragsize %lu != blocksize %lu"
-			"(not supported yet)",
-			sbi->s_frag_size, sb->s_blocksize);
+			"error: fragsize log %u != blocksize log %u",
+			le32_to_cpu(es->s_log_frag_size), sb->s_blocksize_bits);
 		goto failed_mount;
 	}
 
@@ -1066,12 +1057,6 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 			sbi->s_blocks_per_group, sbi->s_inodes_per_group + 3);
 		goto failed_mount;
 	}
-	if (sbi->s_frags_per_group > sb->s_blocksize * 8) {
-		ext2_msg(sb, KERN_ERR,
-			"error: #fragments per group too big: %lu",
-			sbi->s_frags_per_group);
-		goto failed_mount;
-	}
 	if (sbi->s_inodes_per_group < sbi->s_inodes_per_block ||
 	    sbi->s_inodes_per_group > sb->s_blocksize * 8) {
 		ext2_msg(sb, KERN_ERR,