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kill d_instantiate_no_diralias()

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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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-05-28 18:27:19 -04:00
parent b0c6108ecf
commit c971e6a006
3 changed files with 11 additions and 32 deletions
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27
fs/dcache.c
View File

@ -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;

15
fs/fuse/dir.c
View File

@ -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);
fuse_change_entry_timeout(entry, &outarg);
if (d) {
fuse_change_entry_timeout(d, &outarg);
dput(d);
} else {
fuse_change_entry_timeout(entry, &outarg);
}
fuse_invalidate_attr(dir);
return 0;

1
include/linux/dcache.h
View File

@ -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 *);