Commit c88f7dcd authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
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cifs: support nested dfs links over reconnect 



Mounting a dfs link that has nested links was already supported at
mount(2), so make it work over reconnect as well.

Make the following case work:

* mount //root/dfs/link /mnt -o ...
  - final share: /server/share

* in server settings
  - change target folder of /root/dfs/link3 to /server/share2
  - change target folder of /root/dfs/link2 to /root/dfs/link3
  - change target folder of /root/dfs/link to /root/dfs/link2

* mount -o remount,... /mnt
 - refresh all dfs referrals
 - mark current connection for failover
 - cifs_reconnect() reconnects to root server
 - tree_connect()
   * checks that /root/dfs/link2 is a link, then chase it
   * checks that root/dfs/link3 is a link, then chase it
   * finally tree connect to /server/share2

If the mounted share is no longer accessible and a reconnect had been
triggered, the client will retry it from both last referral
path (/root/dfs/link3) and original referral path (/root/dfs/link).

Any new referral paths found while chasing dfs links over reconnect,
it will be updated to TCP_Server_Info::leaf_fullpath, accordingly.

Signed-off-by: default avatarPaulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 71e6864e

fs/cifs/cifs_dfs_ref.c

+2 −57
Original line number Diff line number Diff line
@@ -307,12 +307,8 @@ static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt, 
static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)

{

	struct cifs_sb_info *cifs_sb;

	struct cifs_ses *ses;

	struct cifs_tcon *tcon;

	void *page;

	char *full_path, *root_path;

	unsigned int xid;

	int rc;

	char *full_path;

	struct vfsmount *mnt;



	cifs_dbg(FYI, "in %s\n", __func__);
@@ -324,8 +320,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt) 
	 * the double backslashes usually used in the UNC. This function

	 * gives us the latter, so we must adjust the result.

	 */

	mnt = ERR_PTR(-ENOMEM);



	cifs_sb = CIFS_SB(mntpt->d_sb);

	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {

		mnt = ERR_PTR(-EREMOTE);
@@ -341,60 +335,11 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt) 
	}



	convert_delimiter(full_path, '\\');



	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);



	if (!cifs_sb_master_tlink(cifs_sb)) {

		cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);

		goto free_full_path;

	}



	tcon = cifs_sb_master_tcon(cifs_sb);

	if (!tcon) {

		cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);

		goto free_full_path;

	}



	root_path = kstrdup(tcon->treeName, GFP_KERNEL);

	if (!root_path) {

		mnt = ERR_PTR(-ENOMEM);

		goto free_full_path;

	}

	cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);



	ses = tcon->ses;

	xid = get_xid();



	/*

	 * If DFS root has been expired, then unconditionally fetch it again to

	 * refresh DFS referral cache.

	 */

	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),

			    root_path + 1, NULL, NULL);

	if (!rc) {

		rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,

				    cifs_remap(cifs_sb), full_path + 1,

				    NULL, NULL);

	}



	free_xid(xid);



	if (rc) {

		mnt = ERR_PTR(rc);

		goto free_root_path;

	}

	/*

	 * OK - we were able to get and cache a referral for @full_path.

	 *

	 * Now, pass it down to cifs_mount() and it will retry every available

	 * node server in case of failures - no need to do it here.

	 */

	mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);

	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,

		 full_path + 1, mnt);

	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__, full_path + 1, mnt);



free_root_path:

	kfree(root_path);

free_full_path:

	free_dentry_path(page);

cdda_exit:

fs/cifs/cifs_fs_sb.h

+0 −5
Original line number Diff line number Diff line
@@ -61,11 +61,6 @@ struct cifs_sb_info { 
	/* only used when CIFS_MOUNT_USE_PREFIX_PATH is set */

	char *prepath;



	/*

	 * Canonical DFS path initially provided by the mount call. We might connect to something

	 * different via DFS but we want to keep it to do failover properly.

	 */

	char *origin_fullpath; /* \\HOST\SHARE\[OPTIONAL PATH] */

	/* randomly generated 128-bit number for indexing dfs mount groups in referral cache */

	uuid_t dfs_mount_id;

	/*

fs/cifs/cifsglob.h

+23 −1
Original line number Diff line number Diff line
@@ -697,6 +697,19 @@ struct TCP_Server_Info { 
#endif

#ifdef CONFIG_CIFS_DFS_UPCALL

	bool is_dfs_conn; /* if a dfs connection */

	struct mutex refpath_lock; /* protects leaf_fullpath */

	/*

	 * Canonical DFS full paths that were used to chase referrals in mount and reconnect.

	 *

	 * origin_fullpath: first or original referral path

	 * leaf_fullpath: last referral path (might be changed due to nested links in reconnect)

	 *

	 * current_fullpath: pointer to either origin_fullpath or leaf_fullpath

	 * NOTE: cannot be accessed outside cifs_reconnect() and smb2_reconnect()

	 *

	 * format: \\HOST\SHARE\[OPTIONAL PATH]

	 */

	char *origin_fullpath, *leaf_fullpath, *current_fullpath;

#endif

};
@@ -1097,7 +1110,6 @@ struct cifs_tcon { 
	struct cached_fid crfid; /* Cached root fid */

	/* BB add field for back pointer to sb struct(s)? */

#ifdef CONFIG_CIFS_DFS_UPCALL

	char *dfs_path; /* canonical DFS path */

	struct list_head ulist; /* cache update list */

#endif

};
@@ -1948,4 +1960,14 @@ static inline bool is_tcon_dfs(struct cifs_tcon *tcon) 
		tcon->share_flags & (SHI1005_FLAGS_DFS | SHI1005_FLAGS_DFS_ROOT);

}



static inline bool cifs_is_referral_server(struct cifs_tcon *tcon,

					   const struct dfs_info3_param *ref)

{

	/*

	 * Check if all targets are capable of handling DFS referrals as per

	 * MS-DFSC 2.2.4 RESP_GET_DFS_REFERRAL.

	 */

	return is_tcon_dfs(tcon) || (ref && (ref->flags & DFSREF_REFERRAL_SERVER));

}



#endif	/* _CIFS_GLOB_H */

fs/cifs/cifsproto.h

+4 −1
Original line number Diff line number Diff line
@@ -607,7 +607,7 @@ int smb2_parse_query_directory(struct cifs_tcon *tcon, struct kvec *rsp_iov, 


struct super_block *cifs_get_tcp_super(struct TCP_Server_Info *server);

void cifs_put_tcp_super(struct super_block *sb);

int update_super_prepath(struct cifs_tcon *tcon, char *prefix);

int cifs_update_super_prepath(struct cifs_sb_info *cifs_sb, char *prefix);

char *extract_hostname(const char *unc);

char *extract_sharename(const char *unc);
@@ -634,4 +634,7 @@ static inline int cifs_create_options(struct cifs_sb_info *cifs_sb, int options) 
		return options;

}



struct super_block *cifs_get_tcon_super(struct cifs_tcon *tcon);

void cifs_put_tcon_super(struct super_block *sb);



#endif			/* _CIFSPROTO_H */

fs/cifs/connect.c

+578 −560

File changed.

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