Commit 4ea3ada2 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Al Viro

[PATCH] new helper: d_obtain_alias

The calling conventions of d_alloc_anon are rather unfortunate for all
users, and it's name is not very descriptive either.

Add d_obtain_alias as a new exported helper that drops the inode
reference in the failure case, too and allows to pass-through NULL
pointers and inodes to allow for tail-calls in the export operations.

Incidentally this helper already existed as a private function in
libfs.c as exportfs_d_alloc so kill that one and switch the callers
to d_obtain_alias.
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3a8cff4f
......@@ -1174,6 +1174,41 @@ struct dentry * d_alloc_anon(struct inode *inode)
return res;
}
/**
* d_obtain_alias - find or allocate a dentry for a given inode
* @inode: inode to allocate the dentry for
*
* Obtain a dentry for an inode resulting from NFS filehandle conversion or
* similar open by handle operations. The returned dentry may be anonymous,
* or may have a full name (if the inode was already in the cache).
*
* When called on a directory inode, we must ensure that the inode only ever
* has one dentry. If a dentry is found, that is returned instead of
* allocating a new one.
*
* On successful return, the reference to the inode has been transferred
* to the dentry. If %NULL is returned (indicating kmalloc failure),
* the reference on the inode has been released. To make it easier
* to use in export operations a NULL or IS_ERR inode may be passed in
* and will be casted to the corresponding NULL or IS_ERR dentry.
*/
struct dentry *d_obtain_alias(struct inode *inode)
{
struct dentry *dentry;
if (!inode)
return NULL;
if (IS_ERR(inode))
return ERR_CAST(inode);
dentry = d_alloc_anon(inode);
if (!dentry) {
iput(inode);
dentry = ERR_PTR(-ENOMEM);
}
return dentry;
}
EXPORT_SYMBOL_GPL(d_obtain_alias);
/**
* d_splice_alias - splice a disconnected dentry into the tree if one exists
......
......@@ -732,28 +732,6 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
return ret;
}
/*
* This is what d_alloc_anon should have been. Once the exportfs
* argument transition has been finished I will update d_alloc_anon
* to this prototype and this wrapper will go away. --hch
*/
static struct dentry *exportfs_d_alloc(struct inode *inode)
{
struct dentry *dentry;
if (!inode)
return NULL;
if (IS_ERR(inode))
return ERR_PTR(PTR_ERR(inode));
dentry = d_alloc_anon(inode);
if (!dentry) {
iput(inode);
dentry = ERR_PTR(-ENOMEM);
}
return dentry;
}
/**
* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
* @sb: filesystem to do the file handle conversion on
......@@ -782,7 +760,7 @@ struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
break;
}
return exportfs_d_alloc(inode);
return d_obtain_alias(inode);
}
EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
......@@ -815,7 +793,7 @@ struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
break;
}
return exportfs_d_alloc(inode);
return d_obtain_alias(inode);
}
EXPORT_SYMBOL_GPL(generic_fh_to_parent);
......
......@@ -231,6 +231,7 @@ extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
extern struct dentry * d_alloc_anon(struct inode *);
extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
extern struct dentry * d_obtain_alias(struct inode *);
extern void shrink_dcache_sb(struct super_block *);
extern void shrink_dcache_parent(struct dentry *);
extern void shrink_dcache_for_umount(struct super_block *);
......
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