Commit 2035e776 authored by Theodore Ts'o's avatar Theodore Ts'o
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ext4: check for ext[23] file system features when mounting as ext[23] 



Provide better emulation for ext[23] mode by enforcing that the file
system does not have any unsupported file system features as defined
by ext[23] when emulating the ext[23] file system driver when
CONFIG_EXT4_USE_FOR_EXT23 is defined.

This causes the file system type information in /proc/mounts to be
correct for the automatically mounted root file system.  This also
means that "mount -t ext2 /dev/sda /mnt" will fail if /dev/sda
contains an ext3 or ext4 file system, just as one would expect if the
original ext2 file system driver were in use.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 26626f11

fs/ext4/ext4.h

+15 −0
Original line number Diff line number Diff line
@@ -1351,6 +1351,21 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei) 
#define EXT4_FEATURE_INCOMPAT_EA_INODE		0x0400 /* EA in inode */

#define EXT4_FEATURE_INCOMPAT_DIRDATA		0x1000 /* data in dirent */



#define EXT2_FEATURE_COMPAT_SUPP	EXT4_FEATURE_COMPAT_EXT_ATTR

#define EXT2_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \

					 EXT4_FEATURE_INCOMPAT_META_BG)

#define EXT2_FEATURE_RO_COMPAT_SUPP	(EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \

					 EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \

					 EXT4_FEATURE_RO_COMPAT_BTREE_DIR)



#define EXT3_FEATURE_COMPAT_SUPP	EXT4_FEATURE_COMPAT_EXT_ATTR

#define EXT3_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \

					 EXT4_FEATURE_INCOMPAT_RECOVER| \

					 EXT4_FEATURE_INCOMPAT_META_BG)

#define EXT3_FEATURE_RO_COMPAT_SUPP	(EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \

					 EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \

					 EXT4_FEATURE_RO_COMPAT_BTREE_DIR)



#define EXT4_FEATURE_COMPAT_SUPP	EXT2_FEATURE_COMPAT_EXT_ATTR

#define EXT4_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \

					 EXT4_FEATURE_INCOMPAT_RECOVER| \

fs/ext4/super.c

+65 −9
Original line number Diff line number Diff line
@@ -75,11 +75,27 @@ static void ext4_write_super(struct super_block *sb); 
static int ext4_freeze(struct super_block *sb);

static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags,

		       const char *dev_name, void *data);

static inline int ext2_feature_set_ok(struct super_block *sb);

static inline int ext3_feature_set_ok(struct super_block *sb);

static int ext4_feature_set_ok(struct super_block *sb, int readonly);

static void ext4_destroy_lazyinit_thread(void);

static void ext4_unregister_li_request(struct super_block *sb);

static void ext4_clear_request_list(void);



#if !defined(CONFIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)

static struct file_system_type ext2_fs_type = {

	.owner		= THIS_MODULE,

	.name		= "ext2",

	.mount		= ext4_mount,

	.kill_sb	= kill_block_super,

	.fs_flags	= FS_REQUIRES_DEV,

};

#define IS_EXT2_SB(sb) ((sb)->s_bdev->bd_holder == &ext2_fs_type)

#else

#define IS_EXT2_SB(sb) (0)

#endif





#if !defined(CONFIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)

static struct file_system_type ext3_fs_type = {

	.owner		= THIS_MODULE,
@@ -3187,6 +3203,28 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 
		       "feature flags set on rev 0 fs, "

		       "running e2fsck is recommended");



	if (IS_EXT2_SB(sb)) {

		if (ext2_feature_set_ok(sb))

			ext4_msg(sb, KERN_INFO, "mounting ext2 file system "

				 "using the ext4 subsystem");

		else {

			ext4_msg(sb, KERN_ERR, "couldn't mount as ext2 due "

				 "to feature incompatibilities");

			goto failed_mount;

		}

	}



	if (IS_EXT3_SB(sb)) {

		if (ext3_feature_set_ok(sb))

			ext4_msg(sb, KERN_INFO, "mounting ext3 file system "

				 "using the ext4 subsystem");

		else {

			ext4_msg(sb, KERN_ERR, "couldn't mount as ext3 due "

				 "to feature incompatibilities");

			goto failed_mount;

		}

	}



	/*

	 * Check feature flags regardless of the revision level, since we

	 * previously didn't change the revision level when setting the flags,
@@ -4772,14 +4810,6 @@ static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags, 
}



#if !defined(CONFIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)

static struct file_system_type ext2_fs_type = {

	.owner		= THIS_MODULE,

	.name		= "ext2",

	.mount		= ext4_mount,

	.kill_sb	= kill_block_super,

	.fs_flags	= FS_REQUIRES_DEV,

};



static inline void register_as_ext2(void)

{

	int err = register_filesystem(&ext2_fs_type);
@@ -4792,10 +4822,22 @@ static inline void unregister_as_ext2(void) 
{

	unregister_filesystem(&ext2_fs_type);

}



static inline int ext2_feature_set_ok(struct super_block *sb)

{

	if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP))

		return 0;

	if (sb->s_flags & MS_RDONLY)

		return 1;

	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT2_FEATURE_RO_COMPAT_SUPP))

		return 0;

	return 1;

}

MODULE_ALIAS("ext2");

#else

static inline void register_as_ext2(void) { }

static inline void unregister_as_ext2(void) { }

static inline int ext2_feature_set_ok(struct super_block *sb) { return 0; }

#endif



#if !defined(CONFIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
@@ -4811,10 +4853,24 @@ static inline void unregister_as_ext3(void) 
{

	unregister_filesystem(&ext3_fs_type);

}



static inline int ext3_feature_set_ok(struct super_block *sb)

{

	if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT3_FEATURE_INCOMPAT_SUPP))

		return 0;

	if (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))

		return 0;

	if (sb->s_flags & MS_RDONLY)

		return 1;

	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT3_FEATURE_RO_COMPAT_SUPP))

		return 0;

	return 1;

}

MODULE_ALIAS("ext3");

#else

static inline void register_as_ext3(void) { }

static inline void unregister_as_ext3(void) { }

static inline int ext3_feature_set_ok(struct super_block *sb) { return 0; }

#endif



static struct file_system_type ext4_fs_type = {
@@ -4898,8 +4954,8 @@ static int __init ext4_init_fs(void) 
	err = init_inodecache();

	if (err)

		goto out1;

	register_as_ext2();

	register_as_ext3();

	register_as_ext2();

	err = register_filesystem(&ext4_fs_type);

	if (err)

		goto out;

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