lustre/ptlrpc/sec_ctx.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  *
  19  * http://www.gnu.org/licenses/gpl-2.0.html
  20  *
  21  * GPL HEADER END
  22  */
  23 /*
  24  * Copyright (c) 2014, 2017, Intel Corporation.
  25  */
  26
  27 #define DEBUG_SUBSYSTEM S_FILTER
  28
  29 #include <linux/fs.h>
  30 #include <linux/fs_struct.h>
  31 #include <libcfs/libcfs.h>
  32 #include <lvfs.h>
  33 #include <obd_class.h>
  34
  35 #include "ptlrpc_internal.h"
  36
  37 /* refine later and change to seqlock or simlar from libcfs */
  38 /* Debugging check only needed during development */
  39 #ifdef OBD_CTXT_DEBUG
  40 # define ASSERT_CTXT_MAGIC(magic) LASSERT((magic) == OBD_RUN_CTXT_MAGIC)
  41 #else
  42 # define ASSERT_CTXT_MAGIC(magic) do {} while(0)
  43 #endif
  44
  45 static inline void ll_set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt,
  46                                  struct dentry *dentry)
  47 {
  48         struct path path;
  49         struct path old_pwd;
  50
  51         path.mnt = mnt;
  52         path.dentry = dentry;
  53         path_get(&path);
  54         spin_lock(&fs->lock);
  55         write_seqcount_begin(&fs->seq);
  56         old_pwd = fs->pwd;
  57         fs->pwd = path;
  58         write_seqcount_end(&fs->seq);
  59         spin_unlock(&fs->lock);
  60
  61         if (old_pwd.dentry)
  62                 path_put(&old_pwd);
  63 }
  64
  65 /* push / pop to root of obd store */
  66 void push_ctxt(struct lvfs_run_ctxt *save, struct lvfs_run_ctxt *new_ctx)
  67 {
  68         /* if there is underlaying dt_device then push_ctxt is not needed */
  69         if (new_ctx->dt != NULL)
  70                 return;
  71
  72         ASSERT_CTXT_MAGIC(new_ctx->magic);
  73         OBD_SET_CTXT_MAGIC(save);
  74
  75         save->fs = get_fs();
  76         LASSERT(ll_d_count(current->fs->pwd.dentry));
  77         LASSERT(ll_d_count(new_ctx->pwd));
  78         save->pwd = dget(current->fs->pwd.dentry);
  79         save->pwdmnt = mntget(current->fs->pwd.mnt);
  80         save->umask = current_umask();
  81
  82         LASSERT(save->pwd);
  83         LASSERT(save->pwdmnt);
  84         LASSERT(new_ctx->pwd);
  85         LASSERT(new_ctx->pwdmnt);
  86
  87         current->fs->umask = 0; /* umask already applied on client */
  88         set_fs(new_ctx->fs);
  89         ll_set_fs_pwd(current->fs, new_ctx->pwdmnt, new_ctx->pwd);
  90 }
  91 EXPORT_SYMBOL(push_ctxt);
  92
  93 void pop_ctxt(struct lvfs_run_ctxt *saved, struct lvfs_run_ctxt *new_ctx)
  94 {
  95         /* if there is underlaying dt_device then pop_ctxt is not needed */
  96         if (new_ctx->dt != NULL)
  97                 return;
  98
  99         ASSERT_CTXT_MAGIC(saved->magic);
 100
 101         LASSERTF(current->fs->pwd.dentry == new_ctx->pwd, "%p != %p\n",
 102                  current->fs->pwd.dentry, new_ctx->pwd);
 103         LASSERTF(current->fs->pwd.mnt == new_ctx->pwdmnt, "%p != %p\n",
 104                  current->fs->pwd.mnt, new_ctx->pwdmnt);
 105
 106         set_fs(saved->fs);
 107         ll_set_fs_pwd(current->fs, saved->pwdmnt, saved->pwd);
 108
 109         dput(saved->pwd);
 110         mntput(saved->pwdmnt);
 111         current->fs->umask = saved->umask;
 112 }
 113 EXPORT_SYMBOL(pop_ctxt);