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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
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+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 &&
+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) {