Commit 4c793d4c authored by Jeff Layton's avatar Jeff Layton Committed by Ilya Dryomov
Browse files

ceph: make ceph_msdc_build_path use ref-walk 



Encryption potentially requires allocation, at which point we'll need to
be in a non-atomic context. Convert ceph_msdc_build_path to take dentry
spinlocks and references instead of using rcu_read_lock to walk the
path.

This is slightly less efficient, and we may want to eventually allow
using RCU when the leaf dentry isn't encrypted.

Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: default avatarLuís Henriques <lhenriques@suse.de>
Reviewed-by: default avatarMilind Changire <mchangir@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent ec9595c0

fs/ceph/mds_client.c

+19 −16
Original line number Diff line number Diff line
@@ -2387,7 +2387,8 @@ static inline u64 __get_oldest_tid(struct ceph_mds_client *mdsc) 
char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,

			   int stop_on_nosnap)

{

	struct dentry *temp;

	struct dentry *cur;

	struct inode *inode;

	char *path;

	int pos;

	unsigned seq;
@@ -2404,34 +2405,35 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, 
	path[pos] = '\0';



	seq = read_seqbegin(&rename_lock);

	rcu_read_lock();

	temp = dentry;

	cur = dget(dentry);

	for (;;) {

		struct inode *inode;

		struct dentry *temp;



		spin_lock(&temp->d_lock);

		inode = d_inode(temp);

		spin_lock(&cur->d_lock);

		inode = d_inode(cur);

		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {

			dout("build_path path+%d: %p SNAPDIR\n",

			     pos, temp);

		} else if (stop_on_nosnap && inode && dentry != temp &&

			     pos, cur);

		} else if (stop_on_nosnap && inode && dentry != cur &&

			   ceph_snap(inode) == CEPH_NOSNAP) {

			spin_unlock(&temp->d_lock);

			spin_unlock(&cur->d_lock);

			pos++; /* get rid of any prepended '/' */

			break;

		} else {

			pos -= temp->d_name.len;

			pos -= cur->d_name.len;

			if (pos < 0) {

				spin_unlock(&temp->d_lock);

				spin_unlock(&cur->d_lock);

				break;

			}

			memcpy(path + pos, temp->d_name.name, temp->d_name.len);

			memcpy(path + pos, cur->d_name.name, cur->d_name.len);

		}

		temp = cur;

		spin_unlock(&temp->d_lock);

		temp = READ_ONCE(temp->d_parent);

		cur = dget_parent(temp);

		dput(temp);



		/* Are we at the root? */

		if (IS_ROOT(temp))

		if (IS_ROOT(cur))

			break;



		/* Are we out of buffer? */
@@ -2440,8 +2442,9 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, 


		path[pos] = '/';

	}

	base = ceph_ino(d_inode(temp));

	rcu_read_unlock();

	inode = d_inode(cur);

	base = inode ? ceph_ino(inode) : 0;

	dput(cur);



	if (read_seqretry(&rename_lock, seq))

		goto retry;