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 <libcfs/libcfs.h>
  31 #include <lvfs.h>
  32 #include <obd_class.h>
  33
  34 #include "ptlrpc_internal.h"
  35
  36 /* refine later and change to seqlock or simlar from libcfs */
  37 /* Debugging check only needed during development */
  38 #ifdef OBD_CTXT_DEBUG
  39 # define ASSERT_CTXT_MAGIC(magic) LASSERT((magic) == OBD_RUN_CTXT_MAGIC)
  40 # define ASSERT_NOT_KERNEL_CTXT(msg) LASSERTF(!segment_eq(get_fs(), KERNEL_DS),\
  41                                               msg)
  42 # define ASSERT_KERNEL_CTXT(msg) LASSERTF(segment_eq(get_fs(), KERNEL_DS), msg)
  43 #else
  44 # define ASSERT_CTXT_MAGIC(magic) do {} while(0)
  45 # define ASSERT_NOT_KERNEL_CTXT(msg) do {} while(0)
  46 # define ASSERT_KERNEL_CTXT(msg) do {} while(0)
  47 #endif
  48
  49 static inline void ll_set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt,
  50                                  struct dentry *dentry)
  51 {
  52         struct path path;
  53         struct path old_pwd;
  54
  55         path.mnt = mnt;
  56         path.dentry = dentry;
  57         path_get(&path);
  58         spin_lock(&fs->lock);
  59         write_seqcount_begin(&fs->seq);
  60         old_pwd = fs->pwd;
  61         fs->pwd = path;
  62         write_seqcount_end(&fs->seq);
  63         spin_unlock(&fs->lock);
  64
  65         if (old_pwd.dentry)
  66                 path_put(&old_pwd);
  67 }
  68
  69 /* push / pop to root of obd store */
  70 void push_ctxt(struct lvfs_run_ctxt *save, struct lvfs_run_ctxt *new_ctx)
  71 {
  72         /* if there is underlaying dt_device then push_ctxt is not needed */
  73         if (new_ctx->dt != NULL)
  74                 return;
  75
  76         //ASSERT_NOT_KERNEL_CTXT("already in kernel context!\n");
  77         ASSERT_CTXT_MAGIC(new_ctx->magic);
  78         OBD_SET_CTXT_MAGIC(save);
  79
  80         save->fs = get_fs();
  81         LASSERT(ll_d_count(current->fs->pwd.dentry));
  82         LASSERT(ll_d_count(new_ctx->pwd));
  83         save->pwd = dget(current->fs->pwd.dentry);
  84         save->pwdmnt = mntget(current->fs->pwd.mnt);
  85         save->umask = current_umask();
  86
  87         LASSERT(save->pwd);
  88         LASSERT(save->pwdmnt);
  89         LASSERT(new_ctx->pwd);
  90         LASSERT(new_ctx->pwdmnt);
  91
  92         current->fs->umask = 0; /* umask already applied on client */
  93         set_fs(new_ctx->fs);
  94         ll_set_fs_pwd(current->fs, new_ctx->pwdmnt, new_ctx->pwd);
  95 }
  96 EXPORT_SYMBOL(push_ctxt);
  97
  98 void pop_ctxt(struct lvfs_run_ctxt *saved, struct lvfs_run_ctxt *new_ctx)
  99 {
 100         /* if there is underlaying dt_device then pop_ctxt is not needed */
 101         if (new_ctx->dt != NULL)
 102                 return;
 103
 104         ASSERT_CTXT_MAGIC(saved->magic);
 105         ASSERT_KERNEL_CTXT("popping non-kernel context!\n");
 106
 107         LASSERTF(current->fs->pwd.dentry == new_ctx->pwd, "%p != %p\n",
 108                  current->fs->pwd.dentry, new_ctx->pwd);
 109         LASSERTF(current->fs->pwd.mnt == new_ctx->pwdmnt, "%p != %p\n",
 110                  current->fs->pwd.mnt, new_ctx->pwdmnt);
 111
 112         set_fs(saved->fs);
 113         ll_set_fs_pwd(current->fs, saved->pwdmnt, saved->pwd);
 114
 115         dput(saved->pwd);
 116         mntput(saved->pwdmnt);
 117         current->fs->umask = saved->umask;
 118 }
 119 EXPORT_SYMBOL(pop_ctxt);