fs: port inode_init_owner() to mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

3 files changed, 17 insertions, 22 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8d5008754cc2..43e26e6f6e42 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2845,7 +2845,7 @@ extern int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
 
 /* ialloc.c */
 extern int ext4_mark_inode_used(struct super_block *sb, int ino);
-extern struct inode *__ext4_new_inode(struct user_namespace *, handle_t *,
+extern struct inode *__ext4_new_inode(struct mnt_idmap *, handle_t *,
 				      struct inode *, umode_t,
 				      const struct qstr *qstr, __u32 goal,
 				      uid_t *owner, __u32 i_flags,
@@ -2853,11 +2853,11 @@ extern struct inode *__ext4_new_inode(struct user_namespace *, handle_t *,
 				      int nblocks);
 
 #define ext4_new_inode(handle, dir, mode, qstr, goal, owner, i_flags)          \
-	__ext4_new_inode(&init_user_ns, (handle), (dir), (mode), (qstr),       \
+	__ext4_new_inode(&nop_mnt_idmap, (handle), (dir), (mode), (qstr),      \
 			 (goal), (owner), i_flags, 0, 0, 0)
-#define ext4_new_inode_start_handle(mnt_userns, dir, mode, qstr, goal, owner, \
+#define ext4_new_inode_start_handle(idmap, dir, mode, qstr, goal, owner, \
 				    type, nblocks)		    \
-	__ext4_new_inode((mnt_userns), NULL, (dir), (mode), (qstr), (goal), (owner), \
+	__ext4_new_inode((idmap), NULL, (dir), (mode), (qstr), (goal), (owner), \
 			 0, (type), __LINE__, (nblocks))
 
 
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 63f9bb6e8851..1024b0c02431 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -921,7 +921,7 @@ static int ext4_xattr_credits_for_new_inode(struct inode *dir, mode_t mode,
  * For other inodes, search forward from the parent directory's block
  * group to find a free inode.
  */
-struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
+struct inode *__ext4_new_inode(struct mnt_idmap *idmap,
 			       handle_t *handle, struct inode *dir,
 			       umode_t mode, const struct qstr *qstr,
 			       __u32 goal, uid_t *owner, __u32 i_flags,
@@ -943,6 +943,7 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 	ext4_group_t flex_group;
 	struct ext4_group_info *grp = NULL;
 	bool encrypt = false;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	/* Cannot create files in a deleted directory */
 	if (!dir || !dir->i_nlink)
@@ -975,7 +976,7 @@ struct inode *__ext4_new_inode(struct user_namespace *mnt_userns,
 		inode_fsuid_set(inode, mnt_userns);
 		inode->i_gid = dir->i_gid;
 	} else
-		inode_init_owner(mnt_userns, inode, dir, mode);
+		inode_init_owner(idmap, inode, dir, mode);
 
 	if (ext4_has_feature_project(sb) &&
 	    ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT))
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 74a2c3eae066..d10a508d95cd 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2795,7 +2795,6 @@ static int ext4_add_nondir(handle_t *handle,
 static int ext4_create(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, umode_t mode, bool excl)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, credits, retries = 0;
@@ -2807,7 +2806,7 @@ static int ext4_create(struct mnt_idmap *idmap, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(mnt_userns, dir, mode, &dentry->d_name,
+	inode = ext4_new_inode_start_handle(idmap, dir, mode, &dentry->d_name,
 					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
 	err = PTR_ERR(inode);
@@ -2831,7 +2830,6 @@ retry:
 static int ext4_mknod(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *dentry, umode_t mode, dev_t rdev)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, credits, retries = 0;
@@ -2843,7 +2841,7 @@ static int ext4_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(mnt_userns, dir, mode, &dentry->d_name,
+	inode = ext4_new_inode_start_handle(idmap, dir, mode, &dentry->d_name,
 					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
 	err = PTR_ERR(inode);
@@ -2866,7 +2864,6 @@ retry:
 static int ext4_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 			struct file *file, umode_t mode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, retries = 0;
@@ -2876,7 +2873,7 @@ static int ext4_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 		return err;
 
 retry:
-	inode = ext4_new_inode_start_handle(mnt_userns, dir, mode,
+	inode = ext4_new_inode_start_handle(idmap, dir, mode,
 					    NULL, 0, NULL,
 					    EXT4_HT_DIR,
 			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
@@ -2978,7 +2975,6 @@ out:
 static int ext4_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *dentry, umode_t mode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, err2 = 0, credits, retries = 0;
@@ -2993,7 +2989,7 @@ static int ext4_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(mnt_userns, dir, S_IFDIR | mode,
+	inode = ext4_new_inode_start_handle(idmap, dir, S_IFDIR | mode,
 					    &dentry->d_name,
 					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
@@ -3346,7 +3342,6 @@ out:
 static int ext4_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *dentry, const char *symname)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, len = strlen(symname);
@@ -3375,7 +3370,7 @@ static int ext4_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		  EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3;
 retry:
-	inode = ext4_new_inode_start_handle(mnt_userns, dir, S_IFLNK|S_IRWXUGO,
+	inode = ext4_new_inode_start_handle(idmap, dir, S_IFLNK|S_IRWXUGO,
 					    &dentry->d_name, 0, NULL,
 					    EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
@@ -3725,7 +3720,7 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
 	}
 }
 
-static struct inode *ext4_whiteout_for_rename(struct user_namespace *mnt_userns,
+static struct inode *ext4_whiteout_for_rename(struct mnt_idmap *idmap,
 					      struct ext4_renament *ent,
 					      int credits, handle_t **h)
 {
@@ -3740,7 +3735,7 @@ static struct inode *ext4_whiteout_for_rename(struct user_namespace *mnt_userns,
 	credits += (EXT4_MAXQUOTAS_TRANS_BLOCKS(ent->dir->i_sb) +
 		    EXT4_XATTR_TRANS_BLOCKS + 4);
 retry:
-	wh = ext4_new_inode_start_handle(mnt_userns, ent->dir,
+	wh = ext4_new_inode_start_handle(idmap, ent->dir,
 					 S_IFCHR | WHITEOUT_MODE,
 					 &ent->dentry->d_name, 0, NULL,
 					 EXT4_HT_DIR, credits);
@@ -3768,7 +3763,7 @@ retry:
  * while new_{dentry,inode) refers to the destination dentry/inode
  * This comes from rename(const char *oldpath, const char *newpath)
  */
-static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
+static int ext4_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		       struct dentry *old_dentry, struct inode *new_dir,
 		       struct dentry *new_dentry, unsigned int flags)
 {
@@ -3856,7 +3851,7 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 			goto release_bh;
 		}
 	} else {
-		whiteout = ext4_whiteout_for_rename(mnt_userns, &old, credits, &handle);
+		whiteout = ext4_whiteout_for_rename(idmap, &old, credits, &handle);
 		if (IS_ERR(whiteout)) {
 			retval = PTR_ERR(whiteout);
 			goto release_bh;
@@ -4168,7 +4163,6 @@ static int ext4_rename2(struct mnt_idmap *idmap,
 			struct inode *new_dir, struct dentry *new_dentry,
 			unsigned int flags)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	int err;
 
 	if (unlikely(ext4_forced_shutdown(EXT4_SB(old_dir->i_sb))))
@@ -4187,7 +4181,7 @@ static int ext4_rename2(struct mnt_idmap *idmap,
 					 new_dir, new_dentry);
 	}
 
-	return ext4_rename(mnt_userns, old_dir, old_dentry, new_dir, new_dentry, flags);
+	return ext4_rename(idmap, old_dir, old_dentry, new_dir, new_dentry, flags);
 }
 
 /*