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

fs/dcache.c

+35 −0
Original line number Diff line number Diff line
@@ -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

fs/libfs.c

+2 −24
Original line number Diff line number Diff line
@@ -732,28 +732,6 @@ out: 
	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);

include/linux/dcache.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *);