Commit 48d0cbd1 authored by Sage Weil's avatar Sage Weil
Browse files

ceph: handle racing calls to ceph_init_dentry 



The ->lookup() and prepopulate_readdir() callers are working with unhashed
dentries, so we don't have to worry.  The export.c callers, though, need
to initialize something they got back from d_obtain_alias() and are
potentially racing with other callers.  Make sure we don't return unless
the dentry is properly initialized (by us or someone else).

Reported-by: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Reviewed-by: default avatarYehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent dfabbed6

fs/ceph/dir.c

+12 −9
Original line number Diff line number Diff line
@@ -40,14 +40,6 @@ int ceph_init_dentry(struct dentry *dentry) 
	if (dentry->d_fsdata)

		return 0;



	if (dentry->d_parent == NULL ||   /* nfs fh_to_dentry */

	    ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)

		d_set_d_op(dentry, &ceph_dentry_ops);

	else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)

		d_set_d_op(dentry, &ceph_snapdir_dentry_ops);

	else

		d_set_d_op(dentry, &ceph_snap_dentry_ops);



	di = kmem_cache_alloc(ceph_dentry_cachep, GFP_NOFS | __GFP_ZERO);

	if (!di)

		return -ENOMEM;          /* oh well */
@@ -58,10 +50,21 @@ int ceph_init_dentry(struct dentry *dentry) 
		kmem_cache_free(ceph_dentry_cachep, di);

		goto out_unlock;

	}



	if (dentry->d_parent == NULL ||   /* nfs fh_to_dentry */

	    ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)

		d_set_d_op(dentry, &ceph_dentry_ops);

	else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)

		d_set_d_op(dentry, &ceph_snapdir_dentry_ops);

	else

		d_set_d_op(dentry, &ceph_snap_dentry_ops);



	di->dentry = dentry;

	di->lease_session = NULL;

	dentry->d_fsdata = di;

	dentry->d_time = jiffies;

	/* avoid reordering d_fsdata setup so that the check above is safe */

	smp_mb();

	dentry->d_fsdata = di;

	ceph_dentry_lru_add(dentry);

out_unlock:

	spin_unlock(&dentry->d_lock);

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