Commit 4fbc0c71 authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

ceph: remove the extra slashes in the server path 

It's possible to pass the mount helper a server path that has more
than one contiguous slash character. For example:

  $ mount -t ceph 192.168.195.165:40176:/// /mnt/cephfs/

In the MDS server side the extra slashes of the server path will be
treated as snap dir, and then we can get the following debug logs:

  ceph:  mount opening path //
  ceph:  open_root_inode opening '//'
  ceph:  fill_trace 0000000059b8a3bc is_dentry 0 is_target 1
  ceph:  alloc_inode 00000000dc4ca00b
  ceph:  get_inode created new inode 00000000dc4ca00b 1.ffffffffffffffff ino 1
  ceph:  get_inode on 1=1.ffffffffffffffff got 00000000dc4ca00b

And then when creating any new file or directory under the mount
point, we can hit the following BUG_ON in ceph_fill_trace():

  BUG_ON(ceph_snap(dir) != dvino.snap);

Have the client ignore the extra slashes in the server path when
mounting. This will also canonicalize the path, so that identical mounts
can be consilidated.

1) "//mydir1///mydir//"
2) "/mydir1/mydir"
3) "/mydir1/mydir/"

Regardless of the internal treatment of these paths, the kernel still
stores the original string including the leading '/' for presentation
to userland.

URL: https://tracker.ceph.com/issues/42771


Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent b38c9eb4

fs/ceph/super.c

+102 −20
Original line number Diff line number Diff line
@@ -107,7 +107,6 @@ static int ceph_statfs(struct dentry *dentry, struct kstatfs *buf) 
	return 0;

}





static int ceph_sync_fs(struct super_block *sb, int wait)

{

	struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
@@ -211,7 +210,6 @@ struct ceph_parse_opts_ctx { 


/*

 * Parse the source parameter.  Distinguish the server list from the path.

 * Internally we do not include the leading '/' in the path.

 *

 * The source will look like:

 *     <server_spec>[,<server_spec>...]:[<path>]
@@ -232,12 +230,15 @@ static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc) 


	dev_name_end = strchr(dev_name, '/');

	if (dev_name_end) {

		if (strlen(dev_name_end) > 1) {

		kfree(fsopt->server_path);



		/*

		 * The server_path will include the whole chars from userland

		 * including the leading '/'.

		 */

		fsopt->server_path = kstrdup(dev_name_end, GFP_KERNEL);

		if (!fsopt->server_path)

			return -ENOMEM;

		}

	} else {

		dev_name_end = dev_name + strlen(dev_name);

	}
@@ -461,6 +462,73 @@ static int strcmp_null(const char *s1, const char *s2) 
	return strcmp(s1, s2);

}



/**

 * path_remove_extra_slash - Remove the extra slashes in the server path

 * @server_path: the server path and could be NULL

 *

 * Return NULL if the path is NULL or only consists of "/", or a string

 * without any extra slashes including the leading slash(es) and the

 * slash(es) at the end of the server path, such as:

 * "//dir1////dir2///" --> "dir1/dir2"

 */

static char *path_remove_extra_slash(const char *server_path)

{

	const char *path = server_path;

	const char *cur, *end;

	char *buf, *p;

	int len;



	/* if the server path is omitted */

	if (!path)

		return NULL;



	/* remove all the leading slashes */

	while (*path == '/')

		path++;



	/* if the server path only consists of slashes */

	if (*path == '\0')

		return NULL;



	len = strlen(path);



	buf = kmalloc(len + 1, GFP_KERNEL);

	if (!buf)

		return ERR_PTR(-ENOMEM);



	end = path + len;

	p = buf;

	do {

		cur = strchr(path, '/');

		if (!cur)

			cur = end;



		len = cur - path;



		/* including one '/' */

		if (cur != end)

			len += 1;



		memcpy(p, path, len);

		p += len;



		while (cur <= end && *cur == '/')

			cur++;

		path = cur;

	} while (path < end);



	*p = '\0';



	/*

	 * remove the last slash if there has and just to make sure that

	 * we will get something like "dir1/dir2"

	 */

	if (*(--p) == '/')

		*p = '\0';



	return buf;

}



static int compare_mount_options(struct ceph_mount_options *new_fsopt,

				 struct ceph_options *new_opt,

				 struct ceph_fs_client *fsc)
@@ -468,6 +536,7 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt, 
	struct ceph_mount_options *fsopt1 = new_fsopt;

	struct ceph_mount_options *fsopt2 = fsc->mount_options;

	int ofs = offsetof(struct ceph_mount_options, snapdir_name);

	char *p1, *p2;

	int ret;



	ret = memcmp(fsopt1, fsopt2, ofs);
@@ -480,9 +549,21 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt, 
	ret = strcmp_null(fsopt1->mds_namespace, fsopt2->mds_namespace);

	if (ret)

		return ret;

	ret = strcmp_null(fsopt1->server_path, fsopt2->server_path);



	p1 = path_remove_extra_slash(fsopt1->server_path);

	if (IS_ERR(p1))

		return PTR_ERR(p1);

	p2 = path_remove_extra_slash(fsopt2->server_path);

	if (IS_ERR(p2)) {

		kfree(p1);

		return PTR_ERR(p2);

	}

	ret = strcmp_null(p1, p2);

	kfree(p1);

	kfree(p2);

	if (ret)

		return ret;



	ret = strcmp_null(fsopt1->fscache_uniq, fsopt2->fscache_uniq);

	if (ret)

		return ret;
@@ -788,7 +869,6 @@ static void destroy_caches(void) 
	ceph_fscache_unregister();

}





/*

 * ceph_umount_begin - initiate forced umount.  Tear down down the

 * mount, skipping steps that may hang while waiting for server(s).
@@ -868,9 +948,6 @@ out: 
	return root;

}









/*

 * mount: join the ceph cluster, and open root directory.

 */
@@ -885,7 +962,7 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc, 
	mutex_lock(&fsc->client->mount_mutex);



	if (!fsc->sb->s_root) {

		const char *path;

		const char *path, *p;

		err = __ceph_open_session(fsc->client, started);

		if (err < 0)

			goto out;
@@ -897,17 +974,22 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc, 
				goto out;

		}



		if (!fsc->mount_options->server_path) {

			path = "";

			dout("mount opening path \\t\n");

		} else {

			path = fsc->mount_options->server_path + 1;

			dout("mount opening path %s\n", path);

		p = path_remove_extra_slash(fsc->mount_options->server_path);

		if (IS_ERR(p)) {

			err = PTR_ERR(p);

			goto out;

		}

		/* if the server path is omitted or just consists of '/' */

		if (!p)

			path = "";

		else

			path = p;

		dout("mount opening path '%s'\n", path);



		ceph_fs_debugfs_init(fsc);



		root = open_root_dentry(fsc, path, started);

		kfree(p);

		if (IS_ERR(root)) {

			err = PTR_ERR(root);

			goto out;

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