bfs: extra sanity checking and static inode bitmap

Strengthen validation of BFS superblock against corruption. Make
in-core inode bitmap static part of superblock info structure. Print a
warning when mounting a BFS filesystem created with "-N 512" option as
only 510 files can be created in the root directory. Make the kernel
messages more uniform. Update the 'prefix' passed to bfs_dump_imap() to
match the current naming of operations. White space and comments
cleanup.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Tigran Aivazian <[e-mail]>
Reported-by: Tetsuo Handa <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/bfs/bfs.h

···
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  *	fs/bfs/bfs.h
- *	Copyright (C) 1999 Tigran Aivazian <[e-mail]>
+ *	Copyright (C) 1999-2018 Tigran Aivazian <[e-mail]>
  */
 #ifndef _FS_BFS_BFS_H
 #define _FS_BFS_BFS_H
 
 #include <linux/bfs_fs.h>
+
+/* In theory BFS supports up to 512 inodes, numbered from 2 (for /) up to 513 inclusive.
+   In actual fact, attempting to create the 512th inode (i.e. inode No. 513 or file No. 511)
+   will fail with ENOSPC in bfs_add_entry(): the root directory cannot contain so many entries, counting '..'.
+   So, mkfs.bfs(8) should really limit its -N option to 511 and not 512. For now, we just print a warning
+   if a filesystem is mounted with such "impossible to fill up" number of inodes */
+#define BFS_MAX_LASTI	513
 
 /*
  * BFS file system in-core superblock info
···
 	unsigned long si_freei;
 	unsigned long si_lf_eblk;
 	unsigned long si_lasti;
-	unsigned long *si_imap;
+	DECLARE_BITMAP(si_imap, BFS_MAX_LASTI+1);
 	struct mutex bfs_lock;
 };
 

fs/bfs/dir.c

···
 /*
  *	fs/bfs/dir.c
  *	BFS directory operations.
- *	Copyright (C) 1999,2000  Tigran Aivazian <[e-mail]>
- *      Made endianness-clean by Andrew Stribblehill <[e-mail]> 2005
+ *	Copyright (C) 1999-2018  Tigran Aivazian <[e-mail]>
+ *  Made endianness-clean by Andrew Stribblehill <[e-mail]> 2005
  */
 
 #include <linux/time.h>

fs/bfs/file.c

···
 /*
  *	fs/bfs/file.c
  *	BFS file operations.
- *	Copyright (C) 1999,2000 Tigran Aivazian <[e-mail]>
+ *	Copyright (C) 1999-2018 Tigran Aivazian <[e-mail]>
  *
  *	Make the file block allocation algorithm understand the size
  *	of the underlying block device.

fs/bfs/inode.c

···
 /*
  *	fs/bfs/inode.c
  *	BFS superblock and inode operations.
- *	Copyright (C) 1999-2006 Tigran Aivazian <[e-mail]>
+ *	Copyright (C) 1999-2018 Tigran Aivazian <[e-mail]>
  *	From fs/minix, Copyright (C) 1991, 1992 Linus Torvalds.
- *
- *      Made endianness-clean by Andrew Stribblehill <[e-mail]>, 2005.
+ *	Made endianness-clean by Andrew Stribblehill <[e-mail]>, 2005.
  */
 
 #include <linux/module.h>
···
 {
 	struct bfs_sb_info *info = BFS_SB(inode->i_sb);
 	unsigned int ino = (u16)inode->i_ino;
-        unsigned long i_sblock;
+	unsigned long i_sblock;
 	struct bfs_inode *di;
 	struct buffer_head *bh;
 	int err = 0;
 
-        dprintf("ino=%08x\n", ino);
+	dprintf("ino=%08x\n", ino);
 
 	di = find_inode(inode->i_sb, ino, &bh);
 	if (IS_ERR(di))
···
 	di->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
 	di->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
 	di->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
-        i_sblock = BFS_I(inode)->i_sblock;
+	i_sblock = BFS_I(inode)->i_sblock;
 	di->i_sblock = cpu_to_le32(i_sblock);
 	di->i_eblock = cpu_to_le32(BFS_I(inode)->i_eblock);
 	di->i_eoffset = cpu_to_le32(i_sblock * BFS_BSIZE + inode->i_size - 1);
···
 	mark_buffer_dirty(bh);
 	brelse(bh);
 
-        if (bi->i_dsk_ino) {
+	if (bi->i_dsk_ino) {
 		if (bi->i_sblock)
 			info->si_freeb += bi->i_eblock + 1 - bi->i_sblock;
 		info->si_freei++;
 		clear_bit(ino, info->si_imap);
-		bfs_dump_imap("delete_inode", s);
-        }
+		bfs_dump_imap("evict_inode", s);
+	}
 
 	/*
 	 * If this was the last file, make the previous block
···
 		return;
 
 	mutex_destroy(&info->bfs_lock);
-	kfree(info->si_imap);
 	kfree(info);
 	s->s_fs_info = NULL;
 }
···
 		else
 			strcat(tmpbuf, "0");
 	}
-	printf("BFS-fs: %s: lasti=%08lx <%s>\n",
-				prefix, BFS_SB(s)->si_lasti, tmpbuf);
+	printf("%s: lasti=%08lx <%s>\n", prefix, BFS_SB(s)->si_lasti, tmpbuf);
 	free_page((unsigned long)tmpbuf);
 #endif
 }
···
 	struct buffer_head *bh, *sbh;
 	struct bfs_super_block *bfs_sb;
 	struct inode *inode;
-	unsigned i, imap_len;
+	unsigned i;
 	struct bfs_sb_info *info;
 	int ret = -EINVAL;
 	unsigned long i_sblock, i_eblock, i_eoff, s_size;
···
 	bfs_sb = (struct bfs_super_block *)sbh->b_data;
 	if (le32_to_cpu(bfs_sb->s_magic) != BFS_MAGIC) {
 		if (!silent)
-			printf("No BFS filesystem on %s (magic=%08x)\n", 
-				s->s_id,  le32_to_cpu(bfs_sb->s_magic));
+			printf("No BFS filesystem on %s (magic=%08x)\n", s->s_id,  le32_to_cpu(bfs_sb->s_magic));
 		goto out1;
 	}
 	if (BFS_UNCLEAN(bfs_sb, s) && !silent)
···
 	s->s_magic = BFS_MAGIC;
 
 	if (le32_to_cpu(bfs_sb->s_start) > le32_to_cpu(bfs_sb->s_end) ||
-	    le32_to_cpu(bfs_sb->s_start) < BFS_BSIZE) {
-		printf("Superblock is corrupted\n");
+	    le32_to_cpu(bfs_sb->s_start) < sizeof(struct bfs_super_block) + sizeof(struct bfs_dirent)) {
+		printf("Superblock is corrupted on %s\n", s->s_id);
 		goto out1;
 	}
 
-	info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) /
-					sizeof(struct bfs_inode)
-					+ BFS_ROOT_INO - 1;
-	imap_len = (info->si_lasti / 8) + 1;
-	info->si_imap = kzalloc(imap_len, GFP_KERNEL | __GFP_NOWARN);
-	if (!info->si_imap) {
-		printf("Cannot allocate %u bytes\n", imap_len);
+	info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) / sizeof(struct bfs_inode) + BFS_ROOT_INO - 1;
+	if (info->si_lasti == BFS_MAX_LASTI)
+		printf("WARNING: filesystem %s was created with 512 inodes, the real maximum is 511, mounting anyway\n", s->s_id);
+	else if (info->si_lasti > BFS_MAX_LASTI) {
+		printf("Impossible last inode number %lu > %d on %s\n", info->si_lasti, BFS_MAX_LASTI, s->s_id);
 		goto out1;
 	}
 	for (i = 0; i < BFS_ROOT_INO; i++)
···
 	inode = bfs_iget(s, BFS_ROOT_INO);
 	if (IS_ERR(inode)) {
 		ret = PTR_ERR(inode);
-		goto out2;
+		goto out1;
 	}
 	s->s_root = d_make_root(inode);
 	if (!s->s_root) {
 		ret = -ENOMEM;
-		goto out2;
+		goto out1;
 	}
 
 	info->si_blocks = (le32_to_cpu(bfs_sb->s_end) + 1) >> BFS_BSIZE_BITS;
-	info->si_freeb = (le32_to_cpu(bfs_sb->s_end) + 1
-			- le32_to_cpu(bfs_sb->s_start)) >> BFS_BSIZE_BITS;
+	info->si_freeb = (le32_to_cpu(bfs_sb->s_end) + 1 - le32_to_cpu(bfs_sb->s_start)) >> BFS_BSIZE_BITS;
 	info->si_freei = 0;
 	info->si_lf_eblk = 0;
 
 	/* can we read the last block? */
 	bh = sb_bread(s, info->si_blocks - 1);
 	if (!bh) {
-		printf("Last block not available: %lu\n", info->si_blocks - 1);
+		printf("Last block not available on %s: %lu\n", s->s_id, info->si_blocks - 1);
 		ret = -EIO;
-		goto out3;
+		goto out2;
 	}
 	brelse(bh);
 
···
 			(i_eoff != le32_to_cpu(-1) && i_eoff > s_size) ||
 			i_sblock * BFS_BSIZE > i_eoff) {
 
-			printf("Inode 0x%08x corrupted\n", i);
+			printf("Inode 0x%08x corrupted on %s\n", i, s->s_id);
 
 			brelse(bh);
 			ret = -EIO;
-			goto out3;
+			goto out2;
 		}
 
 		if (!di->i_ino) {
···
 	}
 	brelse(bh);
 	brelse(sbh);
-	bfs_dump_imap("read_super", s);
+	bfs_dump_imap("fill_super", s);
 	return 0;
 
-out3:
+out2:
 	dput(s->s_root);
 	s->s_root = NULL;
-out2:
-	kfree(info->si_imap);
 out1:
 	brelse(sbh);
 out:
···
 	int err = init_inodecache();
 	if (err)
 		goto out1;
-        err = register_filesystem(&bfs_fs_type);
+	err = register_filesystem(&bfs_fs_type);
 	if (err)
 		goto out;
 	return 0;

include/uapi/linux/bfs_fs.h

···
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 /*
  *	include/linux/bfs_fs.h - BFS data structures on disk.
- *	Copyright (C) 1999 Tigran Aivazian <[e-mail]>
+ *	Copyright (C) 1999-2018 Tigran Aivazian <[e-mail]>
  */
 
 #ifndef _LINUX_BFS_FS_H