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Commit a534c8d1 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Eric Van Hensbergen
Browse files

fs/9p: Prevent parallel rename when doing fid_lookup 



During fid lookup we need to make sure that the dentry->d_parent doesn't
change so that we can safely walk the parent dentries. To ensure that
we need to prevent cross directory rename during fid_lookup. Add a
per superblock rename_sem rw_semaphore to prevent parallel fid lookup and
rename.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarVenkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>
parent ebf46264

fs/9p/fid.c

+78 −36
Original line number Diff line number Diff line
@@ -97,6 +97,34 @@ static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any) 
	return ret;

}



/*

 * We need to hold v9ses->rename_sem as long as we hold references

 * to returned path array. Array element contain pointers to

 * dentry names.

 */

static int build_path_from_dentry(struct v9fs_session_info *v9ses,

				  struct dentry *dentry, char ***names)

{

	int n = 0, i;

	char **wnames;

	struct dentry *ds;



	for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)

		n++;



	wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);

	if (!wnames)

		goto err_out;



	for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)

		wnames[i] = (char  *)ds->d_name.name;



	*names = wnames;

	return n;

err_out:

	return -ENOMEM;

}



/**

 * v9fs_fid_lookup - lookup for a fid, try to walk if not found

 * @dentry: dentry to look for fid in
@@ -112,7 +140,7 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 
	int i, n, l, clone, any, access;

	u32 uid;

	struct p9_fid *fid, *old_fid = NULL;

	struct dentry *d, *ds;

	struct dentry *ds;

	struct v9fs_session_info *v9ses;

	char **wnames, *uname;
@@ -139,50 +167,62 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 
	fid = v9fs_fid_find(dentry, uid, any);

	if (fid)

		return fid;



	/*

	 * we don't have a matching fid. To do a TWALK we need

	 * parent fid. We need to prevent rename when we want to

	 * look at the parent.

	 */

	down_read(&v9ses->rename_sem);

	ds = dentry->d_parent;

	fid = v9fs_fid_find(ds, uid, any);

	if (!fid) { /* walk from the root */

		n = 0;

		for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)

			n++;

	if (fid) {

		/* Found the parent fid do a lookup with that */

		fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);

		goto fid_out;

	}

	up_read(&v9ses->rename_sem);



		fid = v9fs_fid_find(ds, uid, any);

		if (!fid) { /* the user is not attached to the fs yet */

	/* start from the root and try to do a lookup */

	fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);

	if (!fid) {

		/* the user is not attached to the fs yet */

		if (access == V9FS_ACCESS_SINGLE)

			return ERR_PTR(-EPERM);



			if (v9fs_proto_dotu(v9ses) ||

				v9fs_proto_dotl(v9ses))

		if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))

				uname = NULL;

		else

			uname = v9ses->uname;



		fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,

				       v9ses->aname);



		if (IS_ERR(fid))

			return fid;



			v9fs_fid_add(ds, fid);

		v9fs_fid_add(dentry->d_sb->s_root, fid);

	}

	} else /* walk from the parent */

		n = 1;



	if (ds == dentry)

	/* If we are root ourself just return that */

	if (dentry->d_sb->s_root == dentry)

		return fid;



	wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);

	if (!wnames)

		return ERR_PTR(-ENOMEM);



	for (d = dentry, i = (n-1); i >= 0; i--, d = d->d_parent)

		wnames[i] = (char *) d->d_name.name;



	/*

	 * Do a multipath walk with attached root.

	 * When walking parent we need to make sure we

	 * don't have a parallel rename happening

	 */

	down_read(&v9ses->rename_sem);

	n  = build_path_from_dentry(v9ses, dentry, &wnames);

	if (n < 0) {

		fid = ERR_PTR(n);

		goto err_out;

	}

	clone = 1;

	i = 0;

	while (i < n) {

		l = min(n - i, P9_MAXWELEM);

		/*

		 * We need to hold rename lock when doing a multipath

		 * walk to ensure none of the patch component change

		 */

		fid = p9_client_walk(fid, l, &wnames[i], clone);

		if (IS_ERR(fid)) {

			if (old_fid) {
@@ -194,15 +234,17 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 
				p9_client_clunk(old_fid);

			}

			kfree(wnames);

			return fid;

			goto err_out;

		}

		old_fid = fid;

		i += l;

		clone = 0;

	}



	kfree(wnames);

fid_out:

	v9fs_fid_add(dentry, fid);

err_out:

	up_read(&v9ses->rename_sem);

	return fid;

}

fs/9p/v9fs.c

+1 −0
Original line number Diff line number Diff line
@@ -237,6 +237,7 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, 
		__putname(v9ses->uname);

		return ERR_PTR(-ENOMEM);

	}

	init_rwsem(&v9ses->rename_sem);



	rc = bdi_setup_and_register(&v9ses->bdi, "9p", BDI_CAP_MAP_COPY);

	if (rc) {

fs/9p/v9fs.h

+1 −0
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ struct v9fs_session_info { 
	struct p9_client *clnt;	/* 9p client */

	struct list_head slist; /* list of sessions registered with v9fs */

	struct backing_dev_info bdi;

	struct rw_semaphore rename_sem;

};



struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,

fs/9p/vfs_inode.c

+10 −3
Original line number Diff line number Diff line
@@ -948,6 +948,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry, 


	sb = dir->i_sb;

	v9ses = v9fs_inode2v9ses(dir);

	/* We can walk d_parent because we hold the dir->i_mutex */

	dfid = v9fs_fid_lookup(dentry->d_parent);

	if (IS_ERR(dfid))

		return ERR_CAST(dfid);
@@ -1055,27 +1056,33 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry, 
		goto clunk_olddir;

	}



	down_write(&v9ses->rename_sem);

	if (v9fs_proto_dotl(v9ses)) {

		retval = p9_client_rename(oldfid, newdirfid,

					(char *) new_dentry->d_name.name);

		if (retval != -ENOSYS)

			goto clunk_newdir;

	}

	if (old_dentry->d_parent != new_dentry->d_parent) {

		/*

		 * 9P .u can only handle file rename in the same directory

		 */



	/* 9P can only handle file rename in the same directory */

	if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {

		P9_DPRINTK(P9_DEBUG_ERROR,

				"old dir and new dir are different\n");

		retval = -EXDEV;

		goto clunk_newdir;

	}



	v9fs_blank_wstat(&wstat);

	wstat.muid = v9ses->uname;

	wstat.name = (char *) new_dentry->d_name.name;

	retval = p9_client_wstat(oldfid, &wstat);



clunk_newdir:

	if (!retval)

		/* successful rename */

		d_move(old_dentry, new_dentry);

	up_write(&v9ses->rename_sem);

	p9_client_clunk(newdirfid);



clunk_olddir:

fs/9p/vfs_super.c

+1 −0
Original line number Diff line number Diff line
@@ -287,4 +287,5 @@ struct file_system_type v9fs_fs_type = { 
	.get_sb = v9fs_get_sb,

	.kill_sb = v9fs_kill_super,

	.owner = THIS_MODULE,

	.fs_flags = FS_RENAME_DOES_D_MOVE,

};