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Subject[PATCH 10/16] kill d_instantiate_no_diralias()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

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>
---
fs/dcache.c | 27 ---------------------------
fs/fuse/dir.c | 15 +++++++++++----
include/linux/dcache.h | 1 -
3 files changed, 11 insertions(+), 32 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 0e8e5de3c48a..a7d9e7a4c283 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -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;
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 56231b31f806..4bbae6ac75c3 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -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;

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 66c6e17e61e5..0b83629a3d8f 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -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 *);
--
2.11.0
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