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Commit c971e6a0 authored by Al Viro's avatar Al Viro
Browse files

kill d_instantiate_no_diralias() 



The only user is fuse_create_new_entry(), and there it's used to
mitigate the same mkdir/open-by-handle race as in nfs_mkdir().
The same solution applies - unhash the mkdir argument, then
call d_splice_alias() and if that returns a reference to preexisting
alias, dput() and report success.  ->mkdir() argument left unhashed
negative with the preexisting alias moved in the right place is just
fine from the ->mkdir() callers point of view.

Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent b0c6108e

fs/dcache.c

+0 −27
Original line number Diff line number Diff line
@@ -1899,33 +1899,6 @@ void d_instantiate_new(struct dentry *entry, struct inode *inode) 
}

EXPORT_SYMBOL(d_instantiate_new);



/**

 * d_instantiate_no_diralias - instantiate a non-aliased dentry

 * @entry: dentry to complete

 * @inode: inode to attach to this dentry

 *

 * Fill in inode information in the entry.  If a directory alias is found, then

 * return an error (and drop inode).  Together with d_materialise_unique() this

 * guarantees that a directory inode may never have more than one alias.

 */

int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)

{

	BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));



	security_d_instantiate(entry, inode);

	spin_lock(&inode->i_lock);

	if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {

		spin_unlock(&inode->i_lock);

		iput(inode);

		return -EBUSY;

	}

	__d_instantiate(entry, inode);

	spin_unlock(&inode->i_lock);



	return 0;

}

EXPORT_SYMBOL(d_instantiate_no_diralias);



struct dentry *d_make_root(struct inode *root_inode)

{

	struct dentry *res = NULL;

fs/fuse/dir.c

+11 −4
Original line number Diff line number Diff line
@@ -539,6 +539,7 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_args *args, 
{

	struct fuse_entry_out outarg;

	struct inode *inode;

	struct dentry *d;

	int err;

	struct fuse_forget_link *forget;
@@ -570,11 +571,17 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_args *args, 
	}

	kfree(forget);



	err = d_instantiate_no_diralias(entry, inode);

	if (err)

		return err;

	d_drop(entry);

	d = d_splice_alias(inode, entry);

	if (IS_ERR(d))

		return PTR_ERR(d);



	if (d) {

		fuse_change_entry_timeout(d, &outarg);

		dput(d);

	} else {

		fuse_change_entry_timeout(entry, &outarg);

	}

	fuse_invalidate_attr(dir);

	return 0;

include/linux/dcache.h

+0 −1
Original line number Diff line number Diff line
@@ -227,7 +227,6 @@ extern void d_instantiate(struct dentry *, struct inode *); 
extern void d_instantiate_new(struct dentry *, struct inode *);

extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);

extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);

extern int d_instantiate_no_diralias(struct dentry *, struct inode *);

extern void __d_drop(struct dentry *dentry);

extern void d_drop(struct dentry *dentry);

extern void d_delete(struct dentry *);