[PATCH 0/2][resend] Make cramfs little endian only

[PATCH 0/2][resend] Make cramfs little endian only

[Andi Drebes]

The following patchset makes cramfs little endian only and updates
the documentation.

I already sent this updated version three weeks ago as a reply in a
discussion (http://marc.info/?l=linux-fsdevel&m=119698067927762&w=2).

As I didn't get any further responses for the updated version (please
let me know if I did something terribly wrong that prevented people from
commenting it) I resend it.

The changes were tested on the following types of machines:
An i386 compatible box (little endian)
UltraSparc IIi (big endian)

Diffed against Linus' git tree.

Signed-off-by: Andi Drebes <andi@programmierforen.de>

[PATCH 1/2][resend] Make cramfs little endian only

[Andi Drebes]

The following patch makes cramfs little endian only.
When trying to mount a big endian image, an error message is produced.

The changes were tested on the following types of machines:
An i386 compatible box (little endian)
UltraSparc IIi (big endian)

Signed-off-by: Andi Drebes <andi@programmierforen.de>
---
 fs/cramfs/inode.c         |  119 ++++++++++++++++++++++++++++++---------------
 include/linux/cramfs_fs.h |   22 ++++----
 2 files changed, 91 insertions(+), 50 deletions(-)

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 350680f..30dc640 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -4,6 +4,10 @@
  * Copyright (C) 1999 Linus Torvalds.
  *
  * This file is released under the GPL.
+ *
+ * Changelog:
+ *	11/07 - Andi Drebes <andi@programmierforen.de>
+ *	Made cramfs little endian only.
  */
 
 /*
@@ -34,13 +38,46 @@ static const struct address_space_operations cramfs_aops;
 
 static DEFINE_MUTEX(read_mutex);
 
+#define CRAMFS_NAMELEN_MASK ((1ul << CRAMFS_NAMELEN_WIDTH)-1)
+#define CRAMFS_MODE_MASK ((1ul << CRAMFS_MODE_WIDTH)-1)
+#define CRAMFS_SIZE_MASK ((1ul << CRAMFS_SIZE_WIDTH)-1)
+
+static inline u32 cramfs_mode(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->mode_uid) & CRAMFS_MODE_MASK;
+}
+
+static inline u32 cramfs_uid(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->mode_uid) >> CRAMFS_MODE_WIDTH;
+}
+
+static inline u32 cramfs_size(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->size_gid) & CRAMFS_SIZE_MASK;
+}
+
+static inline u32 cramfs_gid(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->size_gid) >> CRAMFS_SIZE_WIDTH;
+}
+
+static inline u32 cramfs_offset(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->namelen_offset) >> CRAMFS_NAMELEN_WIDTH;
+}
+
+static inline u32 cramfs_namelen(struct cramfs_inode *inode)
+{
+	return le32_to_cpu(inode->namelen_offset) & CRAMFS_NAMELEN_MASK;
+}
 
 /* These two macros may change in future, to provide better st_ino
    semantics. */
-#define CRAMINO(x)	(((x)->offset && (x)->size)?(x)->offset<<2:1)
+#define CRAMINO(x)	((cramfs_offset(x) && cramfs_size(x)) ? \
+			 cramfs_offset(x) << 2 : 1)
 #define OFFSET(x)	((x)->i_ino)
 
-
 static int cramfs_iget5_test(struct inode *inode, void *opaque)
 {
 	struct cramfs_inode *cramfs_inode = opaque;
@@ -53,13 +90,13 @@ static int cramfs_iget5_test(struct inode *inode, void *opaque)
 
 	/* all empty directories, char, block, pipe, and sock, share inode #1 */
 
-	if ((inode->i_mode != cramfs_inode->mode) ||
-	    (inode->i_gid != cramfs_inode->gid) ||
-	    (inode->i_uid != cramfs_inode->uid))
+	if ((inode->i_mode != cramfs_mode(cramfs_inode)) ||
+	    (inode->i_gid != cramfs_gid(cramfs_inode)) ||
+	    (inode->i_uid != cramfs_uid(cramfs_inode)))
 		return 0; /* does not match */
 
 	if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
-	    (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
+	    (inode->i_rdev != old_decode_dev(cramfs_size(cramfs_inode))))
 		return 0; /* does not match */
 
 	return 1; /* matches */
@@ -69,11 +106,11 @@ static int cramfs_iget5_set(struct inode *inode, void *opaque)
 {
 	static struct timespec zerotime;
 	struct cramfs_inode *cramfs_inode = opaque;
-	inode->i_mode = cramfs_inode->mode;
-	inode->i_uid = cramfs_inode->uid;
-	inode->i_size = cramfs_inode->size;
-	inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
-	inode->i_gid = cramfs_inode->gid;
+	inode->i_mode = cramfs_mode(cramfs_inode);
+	inode->i_uid = cramfs_uid(cramfs_inode);
+	inode->i_size = cramfs_size(cramfs_inode);
+	inode->i_blocks = (cramfs_size(cramfs_inode) - 1) / 512 + 1;
+	inode->i_gid = cramfs_gid(cramfs_inode);
 	/* Struct copy intentional */
 	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 	inode->i_ino = CRAMINO(cramfs_inode);
@@ -94,7 +131,7 @@ static int cramfs_iget5_set(struct inode *inode, void *opaque)
 		inode->i_size = 0;
 		inode->i_blocks = 0;
 		init_special_inode(inode, inode->i_mode,
-			old_decode_dev(cramfs_inode->size));
+			old_decode_dev(cramfs_size(cramfs_inode)));
 	}
 	return 0;
 }
@@ -256,53 +293,57 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 	mutex_unlock(&read_mutex);
 
 	/* Do sanity checks on the superblock */
-	if (super.magic != CRAMFS_MAGIC) {
-		/* check for wrong endianess */
-		if (super.magic == CRAMFS_MAGIC_WEND) {
-			if (!silent)
-				printk(KERN_ERR "cramfs: wrong endianess\n");
-			goto out;
-		}
-
+	if (le32_to_cpu(super.magic) != CRAMFS_MAGIC &&
+	    le32_to_cpu(super.magic) != CRAMFS_MAGIC_WEND) {
 		/* check at 512 byte offset */
 		mutex_lock(&read_mutex);
 		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 		mutex_unlock(&read_mutex);
-		if (super.magic != CRAMFS_MAGIC) {
-			if (super.magic == CRAMFS_MAGIC_WEND && !silent)
-				printk(KERN_ERR "cramfs: wrong endianess\n");
-			else if (!silent)
+
+		if (le32_to_cpu(super.magic) == CRAMFS_MAGIC_WEND)
+			goto other_endian;
+		else if (le32_to_cpu(super.magic) != CRAMFS_MAGIC) {
+			if (!silent)
 				printk(KERN_ERR "cramfs: wrong magic\n");
+
 			goto out;
 		}
 	}
+	/* check for wrong endianess */
+	else if (le32_to_cpu(super.magic) == CRAMFS_MAGIC_WEND) {
+other_endian:
+		if (!silent)
+			printk(KERN_ERR "cramfs: filesystems in big endian format are not supported any longer.\n");
+
+		goto out;
+	}
 
 	/* get feature flags first */
-	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
+	if (le32_to_cpu(super.flags) & ~CRAMFS_SUPPORTED_FLAGS) {
 		printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 		goto out;
 	}
 
 	/* Check that the root inode is in a sane state */
-	if (!S_ISDIR(super.root.mode)) {
+	if (!S_ISDIR(cramfs_mode(&super.root))) {
 		printk(KERN_ERR "cramfs: root is not a directory\n");
 		goto out;
 	}
-	root_offset = super.root.offset << 2;
-	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
-		sbi->size=super.size;
-		sbi->blocks=super.fsid.blocks;
-		sbi->files=super.fsid.files;
+	root_offset = cramfs_offset(&super.root) << 2;
+	if (__le32_to_cpu(super.flags) & CRAMFS_FLAG_FSID_VERSION_2) {
+		sbi->size = le32_to_cpu(super.size);
+		sbi->blocks = le32_to_cpu(super.fsid.blocks);
+		sbi->files = le32_to_cpu(super.fsid.files);
 	} else {
 		sbi->size=1<<28;
 		sbi->blocks=0;
 		sbi->files=0;
 	}
-	sbi->magic=super.magic;
-	sbi->flags=super.flags;
+	sbi->magic = le32_to_cpu(super.magic);
+	sbi->flags = le32_to_cpu(super.flags);
 	if (root_offset == 0)
 		printk(KERN_INFO "cramfs: empty filesystem");
-	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
+	else if (!(le32_to_cpu(super.flags) & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 		 ((root_offset != sizeof(struct cramfs_super)) &&
 		  (root_offset != 512 + sizeof(struct cramfs_super))))
 	{
@@ -383,10 +424,10 @@ static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 		 * and the name padded out to 4-byte boundaries
 		 * with zeroes.
 		 */
-		namelen = de->namelen << 2;
+		namelen = cramfs_namelen(de) << 2;
 		memcpy(buf, name, namelen);
 		ino = CRAMINO(de);
-		mode = de->mode;
+		mode = cramfs_mode(de);
 		mutex_unlock(&read_mutex);
 		nextoffset = offset + sizeof(*de) + namelen;
 		for (;;) {
@@ -432,7 +473,7 @@ static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, s
 		if (sorted && (dentry->d_name.name[0] < name[0]))
 			break;
 
-		namelen = de->namelen << 2;
+		namelen = cramfs_namelen(de) << 2;
 		offset += sizeof(*de) + namelen;
 
 		/* Quick check that the name is roughly the right length */
@@ -484,8 +525,8 @@ static int cramfs_readpage(struct file *file, struct page * page)
 		start_offset = OFFSET(inode) + maxblock*4;
 		mutex_lock(&read_mutex);
 		if (page->index)
-			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
-		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
+			start_offset = le32_to_cpu(*(__le32 *) cramfs_read(sb, blkptr_offset-4, 4));
+		compr_len = le32_to_cpu(*(__le32 *) cramfs_read(sb, blkptr_offset, 4)) - start_offset;
 		mutex_unlock(&read_mutex);
 		pgdata = kmap(page);
 		if (compr_len == 0)
diff --git a/include/linux/cramfs_fs.h b/include/linux/cramfs_fs.h
index 3be4e5a..66aba06 100644
--- a/include/linux/cramfs_fs.h
+++ b/include/linux/cramfs_fs.h
@@ -28,9 +28,9 @@
  * Reasonably terse representation of the inode data.
  */
 struct cramfs_inode {
-	__u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
+	__le32 mode_uid;
 	/* SIZE for device files is i_rdev */
-	__u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
+	__le32 size_gid;
 	/* NAMELEN is the length of the file name, divided by 4 and
            rounded up.  (cramfs doesn't support hard links.) */
 	/* OFFSET: For symlinks and non-empty regular files, this
@@ -39,24 +39,24 @@ struct cramfs_inode {
 	   see README).  For non-empty directories it is the offset
 	   (divided by 4) of the inode of the first file in that
 	   directory.  For anything else, offset is zero. */
-	__u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
+	__le32 namelen_offset;
 };
 
 struct cramfs_info {
-	__u32 crc;
-	__u32 edition;
-	__u32 blocks;
-	__u32 files;
+	__le32 crc;
+	__le32 edition;
+	__le32 blocks;
+	__le32 files;
 };
 
 /*
  * Superblock information at the beginning of the FS.
  */
 struct cramfs_super {
-	__u32 magic;			/* 0x28cd3d45 - random number */
-	__u32 size;			/* length in bytes */
-	__u32 flags;			/* feature flags */
-	__u32 future;			/* reserved for future use */
+	__le32 magic;			/* 0x28cd3d45 - random number */
+	__le32 size;			/* length in bytes */
+	__le32 flags;			/* feature flags */
+	__le32 future;			/* reserved for future use */
 	__u8 signature[16];		/* "Compressed ROMFS" */
 	struct cramfs_info fsid;	/* unique filesystem info */
 	__u8 name[16];			/* user-defined name */
-- 
1.5.1.53.g77e6f

[PATCH 2/2][resend] Make cramfs little endian only: Update documentation

[Andi Drebes]

The following patch updates the cramfs documentation according
to the changes that make cramfs little endian only.

Signed-off-by: Andi Drebes <andi@programmierforen.de>
---
 fs/cramfs/README |   19 +++++--------------
 1 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/fs/cramfs/README b/fs/cramfs/README
index 445d1c2..91efe77 100644
--- a/fs/cramfs/README
+++ b/fs/cramfs/README
@@ -6,8 +6,11 @@ a bit looser, e.g. it doesn't care if the <file_data> items are
 swapped around (though it does care that directory entries (inodes) in
 a given directory are contiguous, as this is used by readdir).
 
-All data is currently in host-endian format; neither mkcramfs nor the
-kernel ever do swabbing.  (See section `Block Size' below.)
+All data is now in little endian format. Before, it was in host endian
+format. In order to make filesystem images more shareable between machines
+with a different byte order, cramfs' specification ("this README file")
+was updated. There will be no support for big endian filesystems in the
+future.
 
 <filesystem>:
 	<superblock>
@@ -108,18 +111,6 @@ kernels, not even necessarily kernels of the same architecture if
 PAGE_CACHE_SIZE is subject to change between kernel versions
 (currently possible with arm and ia64).
 
-The remaining options try to make cramfs more sharable.
-
-One part of that is addressing endianness.  The two options here are
-`always use little-endian' (like ext2fs) or `writer chooses
-endianness; kernel adapts at runtime'.  Little-endian wins because of
-code simplicity and little CPU overhead even on big-endian machines.
-
-The cost of swabbing is changing the code to use the le32_to_cpu
-etc. macros as used by ext2fs.  We don't need to swab the compressed
-data, only the superblock, inodes and block pointers.
-
-
 The other part of making cramfs more sharable is choosing a block
 size.  The options are:
 
-- 
1.5.1.53.g77e6f