[PATCH] Allow d_splice_alias to accept hashed dentries

From: green
Date: Thu Jun 02 2016 - 20:00:14 EST

From: Oleg Drokin <green@xxxxxxxxxxxxxx>

The comment at the top of the function already permits it,
just take out the assetrtion and update __d_add to
be aware of this. Move the BUG_ON to d_add which is the
other user of __d_add and presumably we do not want to
allow hashed dentries as input there.

Signed-off-by: Oleg Drokin <green@xxxxxxxxxxxxxx>
So seeing how there's only one other __d_add user, I just moved the BUG_ON
to d_add and allowed __d_add to not call _d_rehash if the dentry is
already hashed.
This seems to be working as expected and I don't see any problems with it.
Of course I am probably missing some other important consideration ;)

fs/dcache.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index ad4a542..0e35049 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2565,7 +2565,8 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
- _d_rehash(dentry);
+ if (d_unhashed(dentry))
+ _d_rehash(dentry);
if (dir)
end_dir_add(dir, n);
@@ -2584,6 +2585,8 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)

void d_add(struct dentry *entry, struct inode *inode)
+ BUG_ON(!d_unhashed(entry));
if (inode) {
security_d_instantiate(entry, inode);
@@ -2986,8 +2989,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
if (IS_ERR(inode))
return ERR_CAST(inode);

- BUG_ON(!d_unhashed(dentry));
if (!inode)
goto out;