[PATCH] cramfs: generate unique inode number for better inode cache usage

[stefani]

From: Stefani Seibold <stefani@xxxxxxxxxxx>

This patch generates a unique inode numbers for any entries in the cram file
system. For files which did not contain data's (device nodes, fifos and
sockets) the offset of the directory entry inside + 1 will be used as the
inode number.

The + 1 for the inode will it make possible to distinguish between
a file which contains no data and files which has data, the later one has
a inode value where the lower two bits are always 0.

It also reimplement the behavoir to set the size and the number of block
to 0 for special file, which is the right value for devices, fifos and
sockets.

As a little benefit it will be also more compatible which older
mkcramfs, because it will never use the cramfs_inode->offset for
creating a inode number for special files.

Please apply it.

Thanks,
Stefani

Signed-off-by: Stefani Seibold <stefani@xxxxxxxxxxx>
---
 fs/cramfs/inode.c |   99 +++++++++++++++++++++++++++++-----------------------
 1 files changed, 55 insertions(+), 44 deletions(-)

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 32fd5fe..78ab713 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -36,54 +36,61 @@ static DEFINE_MUTEX(read_mutex);
 
 /* 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 OFFSET(x)	((x)->i_ino)
 
-static void setup_inode(struct inode *inode, struct cramfs_inode * cramfs_inode)
+static inline unsigned long cramino(struct cramfs_inode * cino,
+					unsigned int offset)
 {
-	static struct timespec zerotime;
-	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;
-	/* Struct copy intentional */
-	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
-	/* inode->i_nlink is left 1 - arguably wrong for directories,
-	   but it's the best we can do without reading the directory
-	   contents.  1 yields the right result in GNU find, even
-	   without -noleaf option. */
-	if (S_ISREG(inode->i_mode)) {
-		inode->i_fop = &generic_ro_fops;
-		inode->i_data.a_ops = &cramfs_aops;
-	} else if (S_ISDIR(inode->i_mode)) {
-		inode->i_op = &cramfs_dir_inode_operations;
-		inode->i_fop = &cramfs_directory_operations;
-	} else if (S_ISLNK(inode->i_mode)) {
-		inode->i_op = &page_symlink_inode_operations;
-		inode->i_data.a_ops = &cramfs_aops;
-	} else {
-		init_special_inode(inode, inode->i_mode,
-			old_decode_dev(cramfs_inode->size));
-	}
+	if (!cino->offset)
+		return offset + 1;
+	if (!cino->size)
+		return offset + 1;
+	if (S_ISCHR(cino->mode))
+		return offset + 1;
+	if (S_ISBLK(cino->mode))
+		return offset + 1;
+	if (S_ISFIFO(cino->mode))
+		return offset + 1;
+	if (S_ISSOCK(cino->mode))
+		return offset + 1;
+
+	return cino->offset << 2;
 }
 
 static struct inode *get_cramfs_inode(struct super_block *sb,
-				struct cramfs_inode * cramfs_inode)
+	struct cramfs_inode * cramfs_inode, unsigned int offset)
 {
-	struct inode *inode;
-	if (CRAMINO(cramfs_inode) == 1) {
-		inode = new_inode(sb);
-		if (inode) {
-			inode->i_ino = 1;
-			setup_inode(inode, cramfs_inode);
-		}
-	} else {
-		inode = iget_locked(sb, CRAMINO(cramfs_inode));
-		if (inode && (inode->i_state & I_NEW)) {
-			setup_inode(inode, cramfs_inode);
-			unlock_new_inode(inode);
+	static struct timespec zerotime;
+	struct inode *inode = iget_locked(sb, cramino(cramfs_inode, offset));
+
+	if (inode && (inode->i_state & I_NEW)) {
+		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;
+		/* Struct copy intentional */
+		inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
+		/* inode->i_nlink is left 1 - arguably wrong for directories,
+		   but it's the best we can do without reading the directory
+		   contents.  1 yields the right result in GNU find, even
+		   without -noleaf option. */
+		if (S_ISREG(inode->i_mode)) {
+			inode->i_fop = &generic_ro_fops;
+			inode->i_data.a_ops = &cramfs_aops;
+		} else if (S_ISDIR(inode->i_mode)) {
+			inode->i_op = &cramfs_dir_inode_operations;
+			inode->i_fop = &cramfs_directory_operations;
+		} else if (S_ISLNK(inode->i_mode)) {
+			inode->i_op = &page_symlink_inode_operations;
+			inode->i_data.a_ops = &cramfs_aops;
+		} else {
+			inode->i_size = 0;
+			inode->i_blocks = 0;
+			init_special_inode(inode, inode->i_mode,
+				old_decode_dev(cramfs_inode->size));
 		}
+		unlock_new_inode(inode);
 	}
 	return inode;
 }
@@ -265,6 +272,9 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 		printk(KERN_ERR "cramfs: root is not a directory\n");
 		goto out;
 	}
+	/* correct strange, hard-coded permissions of mkcramfs */
+	super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
+
 	root_offset = super.root.offset << 2;
 	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 		sbi->size=super.size;
@@ -289,7 +299,7 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	/* Set it all up.. */
 	sb->s_op = &cramfs_ops;
-	root = get_cramfs_inode(sb, &super.root);
+	root = get_cramfs_inode(sb, &super.root, 0);
 	if (!root)
 		goto out;
 	sb->s_root = d_alloc_root(root);
@@ -365,7 +375,7 @@ static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 		 */
 		namelen = de->namelen << 2;
 		memcpy(buf, name, namelen);
-		ino = CRAMINO(de);
+		ino = cramino(de, OFFSET(inode) + offset);
 		mode = de->mode;
 		mutex_unlock(&read_mutex);
 		nextoffset = offset + sizeof(*de) + namelen;
@@ -404,8 +414,9 @@ static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, s
 		struct cramfs_inode *de;
 		char *name;
 		int namelen, retval;
+		int dir_off = OFFSET(dir) + offset;
 
-		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
+		de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 		name = (char *)(de+1);
 
 		/* Try to take advantage of sorted directories */
@@ -436,7 +447,7 @@ static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, s
 		if (!retval) {
 			struct cramfs_inode entry = *de;
 			mutex_unlock(&read_mutex);
-			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
+			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry, dir_off));
 			return NULL;
 		}
 		/* else (retval < 0) */
-- 
1.7.3.3

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