Commit 3acca043 authored by Al Viro's avatar Al Viro
Browse files

d_path: regularize handling of root dentry in __dentry_path() 



All path-forming primitives boil down to sequence of prepend_name()
on dentries encountered along the way toward root.  Each time we prepend
/ + dentry name to the buffer.  Normally that does exactly what we want,
but there's a corner case when we don't call prepend_name() at all (in case
of __dentry_path() that happens if we are given root dentry).  We obviously
want to end up with "/", rather than "", so this corner case needs to be
handled.

__dentry_path() used to manually put '/' in the end of buffer before
doing anything else, to be overwritten by the first call of prepend_name()
if one happens and to be left in place if we don't call prepend_name() at
all.  That required manually checking that we had space in the buffer
(prepend_name() and prepend() take care of such checks themselves) and lead
to clumsy keeping track of return value.

A better approach is to check if the main loop has added anything
into the buffer and prepend "/" if it hasn't.  A side benefit of using prepend()
is that it does the right thing if we'd already run out of buffer, making
the overflow-handling logics simpler.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3a291c97

fs/d_path.c

+5 −16
Original line number Diff line number Diff line
@@ -329,31 +329,22 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen) 
static char *__dentry_path(const struct dentry *d, char *p, int buflen)

{

	const struct dentry *dentry;

	char *end, *retval;

	char *end;

	int len, seq = 0;

	int error = 0;



	if (buflen < 1)

		goto Elong;



	rcu_read_lock();

restart:

	dentry = d;

	end = p;

	len = buflen;

	/* Get '/' right */

	retval = end-1;

	*retval = '/';

	read_seqbegin_or_lock(&rename_lock, &seq);

	while (!IS_ROOT(dentry)) {

		const struct dentry *parent = dentry->d_parent;



		prefetch(parent);

		error = prepend_name(&end, &len, &dentry->d_name);

		if (error)

		if (unlikely(prepend_name(&end, &len, &dentry->d_name) < 0))

			break;



		retval = end;

		dentry = parent;

	}

	if (!(seq & 1))
@@ -363,11 +354,9 @@ static char *__dentry_path(const struct dentry *d, char *p, int buflen) 
		goto restart;

	}

	done_seqretry(&rename_lock, seq);

	if (error)

		goto Elong;

	return retval;

Elong:

	return ERR_PTR(-ENAMETOOLONG);

	if (len == buflen)

		prepend(&end, &len, "/", 1);

	return len >= 0 ? end : ERR_PTR(-ENAMETOOLONG);

}



char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)