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Commit d79698da authored by Sage Weil's avatar Sage Weil
Browse files

ceph: document unlocked d_parent accesses 



For the most part we don't care about racing with rename when directing
MDS requests; either the old or new parent is fine.  Document that, and
do some minor cleanup.

Reviewed-by: default avatarYehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 41b02e1f

fs/ceph/dir.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -506,7 +506,7 @@ int ceph_handle_snapdir(struct ceph_mds_request *req, 
			struct dentry *dentry, int err)

			struct dentry *dentry, int err)

{

{

	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);

	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);

	struct inode *parent = dentry->d_parent->d_inode;

	struct inode *parent = dentry->d_parent->d_inode; /* we hold i_mutex */





	/* .snap dir? */

	/* .snap dir? */

	if (err == -ENOENT &&

	if (err == -ENOENT &&

fs/ceph/mds_client.c

+10 −3
Original line number Original line Diff line number Diff line
@@ -621,6 +621,12 @@ static void __unregister_request(struct ceph_mds_client *mdsc, 
 */

 */

struct dentry *get_nonsnap_parent(struct dentry *dentry)

struct dentry *get_nonsnap_parent(struct dentry *dentry)

{

{

	/*

	 * we don't need to worry about protecting the d_parent access

	 * here because we never renaming inside the snapped namespace

	 * except to resplice to another snapdir, and either the old or new

	 * result is a valid result.

	 */

	while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP)

	while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP)

		dentry = dentry->d_parent;

		dentry = dentry->d_parent;

	return dentry;

	return dentry;
@@ -656,7 +662,9 @@ static int __choose_mds(struct ceph_mds_client *mdsc, 
	if (req->r_inode) {

	if (req->r_inode) {

		inode = req->r_inode;

		inode = req->r_inode;

	} else if (req->r_dentry) {

	} else if (req->r_dentry) {

		struct inode *dir = req->r_dentry->d_parent->d_inode;

		/* ignore race with rename; old or new d_parent is okay */

		struct dentry *parent = req->r_dentry->d_parent;

		struct inode *dir = parent->d_inode;





		if (dir->i_sb != mdsc->fsc->sb) {

		if (dir->i_sb != mdsc->fsc->sb) {

			/* not this fs! */

			/* not this fs! */
@@ -664,8 +672,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc, 
		} else if (ceph_snap(dir) != CEPH_NOSNAP) {

		} else if (ceph_snap(dir) != CEPH_NOSNAP) {

			/* direct snapped/virtual snapdir requests

			/* direct snapped/virtual snapdir requests

			 * based on parent dir inode */

			 * based on parent dir inode */

			struct dentry *dn =

			struct dentry *dn = get_nonsnap_parent(parent);

				get_nonsnap_parent(req->r_dentry->d_parent);

			inode = dn->d_inode;

			inode = dn->d_inode;

			dout("__choose_mds using nonsnap parent %p\n", inode);

			dout("__choose_mds using nonsnap parent %p\n", inode);

		} else if (req->r_dentry->d_inode) {

		} else if (req->r_dentry->d_inode) {