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SubjectRe: [PATCH 2/3] ensure unique i_ino in filesystems without permanent
linux@horizon.com wrote:
>> Good catch on the inlining. I had meant to do that and missed it.
>
> Er... if you want it to *be* inlined, you have to put it into the .h
> file so the compiler knows about it at the call site. "static inline"
> tells gcc not avoid emitting a callable version.
>
> Something like this the following. (You'll also need to add
> a "#include <stdbool.h>", unless you expand the "bool", "false" and
> "true" macros to their values "_Bool", "0" and "1" by hand.)
>

Doh! Thanks for explaining that. Here's a respun patch with your suggestion
incorporated. Seems to build correctly without stdbool.h. In fact, I don't see
a stdbool.h in Linus' tree as of this morning. Are you sure that it's needed?

Signed-off-by: Jeff Layton <jlayton@redhat.com>

--- linux-2.6/fs/debugfs/inode.c.super
+++ linux-2.6/fs/debugfs/inode.c
@@ -107,7 +107,7 @@ static int debug_fill_super(struct super
{
static struct tree_descr debug_files[] = {{""}};

- return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
+ return registered_fill_super(sb, DEBUGFS_MAGIC, debug_files);
}

static int debug_get_sb(struct file_system_type *fs_type,
--- linux-2.6/fs/fuse/control.c.super
+++ linux-2.6/fs/fuse/control.c
@@ -163,7 +163,7 @@ static int fuse_ctl_fill_super(struct su
struct fuse_conn *fc;
int err;

- err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
+ err = registered_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
if (err)
return err;

--- linux-2.6/fs/libfs.c.super
+++ linux-2.6/fs/libfs.c
@@ -215,7 +215,7 @@ int get_sb_pseudo(struct file_system_typ
s->s_op = ops ? ops : &default_ops;
s->s_time_gran = 1;
root = new_inode(s);
- if (!root)
+ if (!root || iunique_register(root, 0))
goto Enomem;
root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
root->i_uid = root->i_gid = 0;
@@ -356,7 +356,8 @@ int simple_commit_write(struct file *fil
return 0;
}

-int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
+int __simple_fill_super(struct super_block *s, int magic,
+ struct tree_descr *files, bool registered)
{
static struct super_operations s_ops = {.statfs = simple_statfs};
struct inode *inode;
@@ -380,6 +381,12 @@ int simple_fill_super(struct super_block
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
inode->i_nlink = 2;
+ /*
+ * set this as high as a 32 bit val as possible to avoid collisions.
+ * This is also well above the highest value that iunique_register
+ * will assign to an inode
+ */
+ inode->i_ino = 0xffffffff;
root = d_alloc_root(inode);
if (!root) {
iput(inode);
@@ -394,12 +401,15 @@ int simple_fill_super(struct super_block
inode = new_inode(s);
if (!inode)
goto out;
+ if (!registered)
+ inode->i_ino = i;
+ else if (iunique_register(inode, 0))
+ goto out;
inode->i_mode = S_IFREG | files->mode;
inode->i_uid = inode->i_gid = 0;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_fop = files->ops;
- inode->i_ino = i;
d_add(dentry, inode);
}
s->s_root = root;
--- linux-2.6/include/linux/fs.h.super
+++ linux-2.6/include/linux/fs.h
@@ -1879,10 +1879,35 @@ extern const struct file_operations simp
extern struct inode_operations simple_dir_inode_operations;
struct tree_descr { char *name; const struct file_operations *ops; int mode; };
struct dentry *d_alloc_name(struct dentry *, const char *);
-extern int simple_fill_super(struct super_block *, int, struct tree_descr *);
+extern int __simple_fill_super(struct super_block *s, int magic,
+ struct tree_descr *files, bool registered);
extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
extern void simple_release_fs(struct vfsmount **mount, int *count);

+/*
+ * Fill a superblock with a standard set of fields, and add the entries in the
+ * "files" struct. Assign i_ino values to the files sequentially. This function
+ * is appropriate for filesystems that need a particular i_ino value assigned
+ * to a particular "files" entry.
+ */
+static inline int simple_fill_super(struct super_block *s, int magic,
+ struct tree_descr *files)
+{
+ return __simple_fill_super(s, magic, files, false);
+}
+
+/*
+ * Just like simple_fill_super, but does an iunique_register on the inodes
+ * created for "files" entries. This function is appropriate when you don't
+ * need a particular i_ino value assigned to each files entry, and when the
+ * filesystem will have other registered inodes.
+ */
+static inline int registered_fill_super(struct super_block *s, int magic,
+ struct tree_descr *files)
+{
+ return __simple_fill_super(s, magic, files, true);
+}
+
extern ssize_t simple_read_from_buffer(void __user *, size_t, loff_t *, const void *, size_t);

#ifdef CONFIG_MIGRATION
--- linux-2.6/security/inode.c.super
+++ linux-2.6/security/inode.c
@@ -130,7 +130,7 @@ static int fill_super(struct super_block
{
static struct tree_descr files[] = {{""}};

- return simple_fill_super(sb, SECURITYFS_MAGIC, files);
+ return registered_fill_super(sb, SECURITYFS_MAGIC, files);
}

static int get_sb(struct file_system_type *fs_type,
-
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