[CIFS] DFS support: provide shrinkable mounts

Signed-off-by: Igor Mammedov <niallain@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 375 insertions, 0 deletions

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
new file mode 100644
index 000000000000..15e31f8435ba
--- /dev/null
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -0,0 +1,375 @@
+/*
+ *   Contains the CIFS DFS referral mounting routines used for handling
+ *   traversal via DFS junction point
+ *
+ *   Copyright (c) 2007 Igor Mammedov
+ *   Author(s): Igor Mammedov (niallain@gmail.com)
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation; either version
+ *   2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/dcache.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/vfs.h>
+#include <linux/fs.h>
+#include "cifsglob.h"
+#include "cifsproto.h"
+#include "cifsfs.h"
+#include "dns_resolve.h"
+#include "cifs_debug.h"
+
+LIST_HEAD(cifs_dfs_automount_list);
+
+/*
+ * DFS functions
+*/
+
+void dfs_shrink_umount_helper(struct vfsmount *vfsmnt)
+{
+        mark_mounts_for_expiry(&cifs_dfs_automount_list);
+        mark_mounts_for_expiry(&cifs_dfs_automount_list);
+        shrink_submounts(vfsmnt, &cifs_dfs_automount_list);
+}
+
+/**
+ * cifs_get_share_name  -       extracts share name from UNC
+ * @node_name:  pointer to UNC string
+ *
+ * Extracts sharename form full UNC.
+ * i.e. strips from UNC trailing path that is not part of share
+ * name and fixup missing '\' in the begining of DFS node refferal
+ * if neccessary.
+ * Returns pointer to share name on success or NULL on error.
+ * Caller is responsible for freeing returned string.
+ */
+static char *cifs_get_share_name(const char *node_name)
+{
+        int len;
+        char *UNC;
+        char *pSep;
+
+        len = strlen(node_name);
+        UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
+                         GFP_KERNEL);
+        if (!UNC)
+                return NULL;
+
+        /* get share name and server name */
+        if (node_name[1] != '\\') {
+                UNC[0] = '\\';
+                strncpy(UNC+1, node_name, len);
+                len++;
+                UNC[len] = 0;
+        } else {
+                strncpy(UNC, node_name, len);
+                UNC[len] = 0;
+        }
+
+        /* find server name end */
+        pSep = memchr(UNC+2, '\\', len-2);
+        if (!pSep) {
+                cERROR(1, ("%s: no server name end in node name: %s",
+                        __FUNCTION__, node_name));
+                kfree(UNC);
+                return NULL;
+        }
+
+        /* find sharename end */
+        pSep++;
+        pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
+        if (!pSep) {
+                cERROR(1, ("%s:2 cant find share name in node name: %s",
+                        __FUNCTION__, node_name));
+                kfree(UNC);
+                return NULL;
+        }
+        /* trim path up to sharename end
+         *          * now we have share name in UNC */
+        *pSep = 0;
+
+        return UNC;
+}
+
+
+/**
+ * compose_mount_options        -       creates mount options for refferral
+ * @sb_mountdata:       parent/root DFS mount options (template)
+ * @ref_unc:            refferral server UNC
+ * @devname:            pointer for saving device name
+ *
+ * creates mount options for submount based on template options sb_mountdata
+ * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
+ *
+ * Returns: pointer to new mount options or ERR_PTR.
+ * Caller is responcible for freeing retunrned value if it is not error.
+ */
+char *compose_mount_options(const char *sb_mountdata, const char *ref_unc,
+                                char **devname)
+{
+        int rc;
+        char *mountdata;
+        int md_len;
+        char *tkn_e;
+        char *srvIP = NULL;
+        char sep = ',';
+        int off, noff;
+
+        if (sb_mountdata == NULL)
+                return ERR_PTR(-EINVAL);
+
+        *devname = cifs_get_share_name(ref_unc);
+        rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
+        if (rc != 0) {
+                cERROR(1, ("%s: Failed to resolve server part of %s to IP",
+                          __FUNCTION__, *devname));
+                mountdata = ERR_PTR(rc);
+                goto compose_mount_options_out;
+        }
+        md_len = strlen(sb_mountdata) + strlen(srvIP) + strlen(ref_unc) + 3;
+        mountdata = kzalloc(md_len+1, GFP_KERNEL);
+        if (mountdata == NULL) {
+                mountdata = ERR_PTR(-ENOMEM);
+                goto compose_mount_options_out;
+        }
+
+        /* copy all options except of unc,ip,prefixpath */
+        off = 0;
+        if (strncmp(sb_mountdata, "sep=", 4) == 0) {
+                        sep = sb_mountdata[4];
+                        strncpy(mountdata, sb_mountdata, 5);
+                        off += 5;
+        }
+        while ((tkn_e = strchr(sb_mountdata+off, sep))) {
+                noff = (tkn_e - (sb_mountdata+off)) + 1;
+                if (strnicmp(sb_mountdata+off, "unc=", 4) == 0) {
+                        off += noff;
+                        continue;
+                }
+                if (strnicmp(sb_mountdata+off, "ip=", 3) == 0) {
+                        off += noff;
+                        continue;
+                }
+                if (strnicmp(sb_mountdata+off, "prefixpath=", 3) == 0) {
+                        off += noff;
+                        continue;
+                }
+                strncat(mountdata, sb_mountdata+off, noff);
+                off += noff;
+        }
+        strcat(mountdata, sb_mountdata+off);
+        mountdata[md_len] = '\0';
+
+        /* copy new IP and ref share name */
+        strcat(mountdata, ",ip=");
+        strcat(mountdata, srvIP);
+        strcat(mountdata, ",unc=");
+        strcat(mountdata, *devname);
+
+        /* find & copy prefixpath */
+        tkn_e = strchr(ref_unc+2, '\\');
+        if (tkn_e) {
+                tkn_e = strchr(tkn_e+1, '\\');
+                if (tkn_e) {
+                        strcat(mountdata, ",prefixpath=");
+                        strcat(mountdata, tkn_e);
+                }
+        }
+
+        /*cFYI(1,("%s: parent mountdata: %s", __FUNCTION__,sb_mountdata));*/
+        /*cFYI(1, ("%s: submount mountdata: %s", __FUNCTION__, mountdata ));*/
+
+compose_mount_options_out:
+        kfree(srvIP);
+        return mountdata;
+}
+
+
+struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
+                struct dentry *dentry, char *ref_unc)
+{
+        struct cifs_sb_info *cifs_sb;
+        struct vfsmount *mnt;
+        char *mountdata;
+        char *devname;
+
+        cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
+        mountdata = compose_mount_options(cifs_sb->mountdata,
+                                                ref_unc, &devname);
+
+        if (IS_ERR(mountdata))
+                return (struct vfsmount *)mountdata;
+
+        mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
+        kfree(mountdata);
+        kfree(devname);
+        return mnt;
+
+}
+
+static char *build_full_dfs_path_from_dentry(struct dentry *dentry)
+{
+        char *full_path = NULL;
+        char *search_path;
+        char *tmp_path;
+        size_t l_max_len;
+        struct cifs_sb_info *cifs_sb;
+
+        if (dentry->d_inode == NULL)
+                return NULL;
+
+        cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
+
+        if (cifs_sb->tcon == NULL)
+                return NULL;
+
+        search_path = build_path_from_dentry(dentry);
+        if (search_path == NULL)
+                return NULL;
+
+        if (cifs_sb->tcon->Flags & SMB_SHARE_IS_IN_DFS) {
+                /* we should use full path name to correct working with DFS */
+                l_max_len = strnlen(cifs_sb->tcon->treeName, MAX_TREE_SIZE+1) +
+                                        strnlen(search_path, MAX_PATHCONF) + 1;
+                tmp_path = kmalloc(l_max_len, GFP_KERNEL);
+                if (tmp_path == NULL) {
+                        kfree(search_path);
+                        return NULL;
+                }
+                strncpy(tmp_path, cifs_sb->tcon->treeName, l_max_len);
+                strcat(tmp_path, search_path);
+                tmp_path[l_max_len-1] = 0;
+                full_path = tmp_path;
+                kfree(search_path);
+        } else {
+                full_path = search_path;
+        }
+        return full_path;
+}
+
+static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
+                                struct list_head *mntlist)
+{
+        /* stolen from afs code */
+        int err;
+
+        mntget(newmnt);
+        err = do_add_mount(newmnt, nd, nd->mnt->mnt_flags, mntlist);
+        switch (err) {
+        case 0:
+                dput(nd->dentry);
+                mntput(nd->mnt);
+                nd->mnt = newmnt;
+                nd->dentry = dget(newmnt->mnt_root);
+                break;
+        case -EBUSY:
+                /* someone else made a mount here whilst we were busy */
+                while (d_mountpoint(nd->dentry) &&
+                       follow_down(&nd->mnt, &nd->dentry))
+                        ;
+                err = 0;
+        default:
+                mntput(newmnt);
+                break;
+        }
+        return err;
+}
+
+void dump_referral(const struct dfs_info3_param *ref)
+{
+        cFYI(1, ("DFS: ref path: %s", ref->path_name));
+        cFYI(1, ("DFS: node path: %s", ref->node_name));
+        cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
+        cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
+                                ref->PathConsumed));
+}
+
+
+static void*
+cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
+{
+        struct dfs_info3_param *referrals = NULL;
+        unsigned int num_referrals = 0;
+        struct cifs_sb_info *cifs_sb;
+        struct cifsSesInfo *ses;
+        char *full_path = NULL;
+        int xid, i;
+        int rc = 0;
+        struct vfsmount *mnt = ERR_PTR(-ENOENT);
+
+        cFYI(1, ("in %s", __FUNCTION__));
+        BUG_ON(IS_ROOT(dentry));
+
+        xid = GetXid();
+
+        dput(nd->dentry);
+        nd->dentry = dget(dentry);
+
+        cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
+        ses = cifs_sb->tcon->ses;
+
+        if (!ses) {
+                rc = -EINVAL;
+                goto out_err;
+        }
+
+        full_path = build_full_dfs_path_from_dentry(dentry);
+        if (full_path == NULL) {
+                rc = -ENOMEM;
+                goto out_err;
+        }
+
+        rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
+                &num_referrals, &referrals,
+                cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
+
+        for (i = 0; i < num_referrals; i++) {
+                dump_referral(referrals+i);
+                /* connect to a storage node */
+                if (referrals[i].flags & DFSREF_STORAGE_SERVER) {
+                        int len;
+                        len = strlen(referrals[i].node_name);
+                        if (len < 2) {
+                                cERROR(1, ("%s: Net Address path too short: %s",
+                                        __FUNCTION__, referrals[i].node_name));
+                                rc = -EINVAL;
+                                goto out_err;
+                        }
+                        mnt = cifs_dfs_do_refmount(nd->mnt, nd->dentry,
+                                                referrals[i].node_name);
+                        cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p",
+                                         __FUNCTION__,
+                                        referrals[i].node_name, mnt));
+
+                        /* complete mount procedure if we accured submount */
+                        if (!IS_ERR(mnt))
+                                break;
+                }
+        }
+
+        /* we need it cause for() above could exit without valid submount */
+        rc = PTR_ERR(mnt);
+        if (IS_ERR(mnt))
+                goto out_err;
+
+        nd->mnt->mnt_flags |= MNT_SHRINKABLE;
+        rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
+
+out:
+        FreeXid(xid);
+        free_dfs_info_array(referrals, num_referrals);
+        kfree(full_path);
+        cFYI(1, ("leaving %s" , __FUNCTION__));
+        return ERR_PTR(rc);
+out_err:
+        path_release(nd);
+        goto out;
+}
+
+struct inode_operations cifs_dfs_referral_inode_operations = {
+        .follow_link = cifs_dfs_follow_mountpoint,
+};
+