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Commit 3e7e241f authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
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[PATCH] dcache: Add helper d_hash_and_lookup 



It is very common to hash a dentry and then to call lookup.  If we take fs
specific hash functions into account the full hash logic can get ugly.
Further full_name_hash as an inline function is almost 100 bytes on x86 so
having a non-inline choice in some cases can measurably decrease code size.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 92476d7f

fs/dcache.c

+28 −16
Original line number Diff line number Diff line
@@ -1100,6 +1100,32 @@ struct dentry * __d_lookup(struct dentry * parent, struct qstr * name) 
 	return found;

}



/**

 * d_hash_and_lookup - hash the qstr then search for a dentry

 * @dir: Directory to search in

 * @name: qstr of name we wish to find

 *

 * On hash failure or on lookup failure NULL is returned.

 */

struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)

{

	struct dentry *dentry = NULL;



	/*

	 * Check for a fs-specific hash function. Note that we must

	 * calculate the standard hash first, as the d_op->d_hash()

	 * routine may choose to leave the hash value unchanged.

	 */

	name->hash = full_name_hash(name->name, name->len);

	if (dir->d_op && dir->d_op->d_hash) {

		if (dir->d_op->d_hash(dir, name) < 0)

			goto out;

	}

	dentry = d_lookup(dir, name);

out:

	return dentry;

}



/**

 * d_validate - verify dentry provided from insecure source

 * @dentry: The dentry alleged to be valid child of @dparent
@@ -1616,26 +1642,12 @@ ino_t find_inode_number(struct dentry *dir, struct qstr *name) 
	struct dentry * dentry;

	ino_t ino = 0;



	/*

	 * Check for a fs-specific hash function. Note that we must

	 * calculate the standard hash first, as the d_op->d_hash()

	 * routine may choose to leave the hash value unchanged.

	 */

	name->hash = full_name_hash(name->name, name->len);

	if (dir->d_op && dir->d_op->d_hash)

	{

		if (dir->d_op->d_hash(dir, name) != 0)

			goto out;

	}



	dentry = d_lookup(dir, name);

	if (dentry)

	{

	dentry = d_hash_and_lookup(dir, name);

	if (dentry) {

		if (dentry->d_inode)

			ino = dentry->d_inode->i_ino;

		dput(dentry);

	}

out:

	return ino;

}

include/linux/dcache.h

+1 −0
Original line number Diff line number Diff line
@@ -275,6 +275,7 @@ extern void d_move(struct dentry *, struct dentry *); 
/* appendix may either be NULL or be used for transname suffixes */

extern struct dentry * d_lookup(struct dentry *, struct qstr *);

extern struct dentry * __d_lookup(struct dentry *, struct qstr *);

extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);



/* validate "insecure" dentry pointer */

extern int d_validate(struct dentry *, struct dentry *);