lustre/kernel_patches/patches/quota-umount-race-fix.patch

   1
   2 From: Jan Kara <jack@suse.cz>
   3
   4 Fix possible races between umount and quota on/off.
   5
   6 Finally I decided to take a reference to vfsmount during vfs_quota_on() and
   7 to drop it after the final cleanup in the vfs_quota_off().  This way we
   8 should be all the time guarded against umount.  This way was protected also
   9 the old code which used filp_open() for opening quota files.  I was also
  10 thinking about other ways of protection but there would be always a window
  11 (provided I don't want to play much with namespace locks) where
  12 vfs_quota_on() could be called while umount() is in progress resulting in
  13 the "Busy inodes after unmount" messages...
  14
  15 Get a reference to vfsmount during quotaon() so that we are guarded against
  16 umount (as was the old code using filp_open()).
  17
  18 Signed-off-by: Jan Kara <jack@suse.cz>
  19 Signed-off-by: Andrew Morton <akpm@osdl.org>
  20 ---
  21
  22  25-akpm/fs/dquot.c               |   45 ++++++++++++++++++++++++++++-----------
  23  25-akpm/include/linux/quota.h    |    1
  24  25-akpm/include/linux/quotaops.h |    2 -
  25  3 files changed, 35 insertions(+), 13 deletions(-)
  26
  27 diff -puN fs/dquot.c~quota-umount-race-fix fs/dquot.c
  28 --- 25/fs/dquot.c~quota-umount-race-fix Tue Nov 23 17:11:34 2004
  29 +++ 25-akpm/fs/dquot.c  Tue Nov 23 17:11:34 2004
  30 @@ -1314,12 +1314,14 @@ int vfs_quota_off(struct super_block *sb
  31  {
  32         int cnt;
  33         struct quota_info *dqopt = sb_dqopt(sb);
  34 -       struct inode *toput[MAXQUOTAS];
  35 +       struct inode *toputinode[MAXQUOTAS];
  36 +       struct vfsmount *toputmnt[MAXQUOTAS];
  37
  38         /* We need to serialize quota_off() for device */
  39         down(&dqopt->dqonoff_sem);
  40         for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
  41 -               toput[cnt] = NULL;
  42 +               toputinode[cnt] = NULL;
  43 +               toputmnt[cnt] = NULL;
  44                 if (type != -1 && cnt != type)
  45                         continue;
  46                 if (!sb_has_quota_enabled(sb, cnt))
  47 @@ -1339,8 +1341,10 @@ int vfs_quota_off(struct super_block *sb
  48                         dqopt->ops[cnt]->free_file_info(sb, cnt);
  49                 put_quota_format(dqopt->info[cnt].dqi_format);
  50
  51 -               toput[cnt] = dqopt->files[cnt];
  52 +               toputinode[cnt] = dqopt->files[cnt];
  53 +               toputmnt[cnt] = dqopt->mnt[cnt];
  54                 dqopt->files[cnt] = NULL;
  55 +               dqopt->mnt[cnt] = NULL;
  56                 dqopt->info[cnt].dqi_flags = 0;
  57                 dqopt->info[cnt].dqi_igrace = 0;
  58                 dqopt->info[cnt].dqi_bgrace = 0;
  59 @@ -1348,7 +1352,10 @@ int vfs_quota_off(struct super_block *sb
  60         }
  61         up(&dqopt->dqonoff_sem);
  62         /* Sync the superblock so that buffers with quota data are written to
  63 -         * disk (and so userspace sees correct data afterwards) */
  64 +        * disk (and so userspace sees correct data afterwards).
  65 +        * The reference to vfsmnt we are still holding protects us from
  66 +        * umount (we don't have it only when quotas are turned on/off for
  67 +        * journal replay but in that case we are guarded by the fs anyway). */
  68         if (sb->s_op->sync_fs)
  69                 sb->s_op->sync_fs(sb, 1);
  70         sync_blockdev(sb->s_bdev);
  71 @@ -1358,13 +1365,24 @@ int vfs_quota_off(struct super_block *sb
  72          * must also discard the blockdev buffers so that we see the
  73          * changes done by userspace on the next quotaon() */
  74         for (cnt = 0; cnt < MAXQUOTAS; cnt++)
  75 -               if (toput[cnt]) {
  76 -                       down(&toput[cnt]->i_sem);
  77 -                       toput[cnt]->i_flags &= ~(S_IMMUTABLE | S_NOATIME | S_NOQUOTA);
  78 -                       truncate_inode_pages(&toput[cnt]->i_data, 0);
  79 -                       up(&toput[cnt]->i_sem);
  80 -                       mark_inode_dirty(toput[cnt]);
  81 -                       iput(toput[cnt]);
  82 +               if (toputinode[cnt]) {
  83 +                       down(&dqopt->dqonoff_sem);
  84 +                       /* If quota was reenabled in the meantime, we have
  85 +                        * nothing to do */
  86 +                       if (!sb_has_quota_enabled(sb, cnt)) {
  87 +                               down(&toputinode[cnt]->i_sem);
  88 +                               toputinode[cnt]->i_flags &= ~(S_IMMUTABLE |
  89 +                                 S_NOATIME | S_NOQUOTA);
  90 +                               truncate_inode_pages(&toputinode[cnt]->i_data, 0);
  91 +                               up(&toputinode[cnt]->i_sem);
  92 +                               mark_inode_dirty(toputinode[cnt]);
  93 +                               iput(toputinode[cnt]);
  94 +                       }
  95 +                       up(&dqopt->dqonoff_sem);
  96 +                       /* We don't hold the reference when we turned on quotas
  97 +                        * just for the journal replay... */
  98 +                       if (toputmnt[cnt])
  99 +                               mntput(toputmnt[cnt]);
 100                 }
 101         invalidate_bdev(sb->s_bdev, 0);
 102         return 0;
 103 @@ -1478,8 +1496,11 @@ int vfs_quota_on(struct super_block *sb,
 104         /* Quota file not on the same filesystem? */
 105         if (nd.mnt->mnt_sb != sb)
 106                 error = -EXDEV;
 107 -       else
 108 +       else {
 109                 error = vfs_quota_on_inode(nd.dentry->d_inode, type, format_id);
 110 +               if (!error)
 111 +                       sb_dqopt(sb)->mnt[type] = mntget(nd.mnt);
 112 +       }
 113  out_path:
 114         path_release(&nd);
 115         return error;
 116 diff -puN include/linux/quota.h~quota-umount-race-fix include/linux/quota.h
 117 --- 25/include/linux/quota.h~quota-umount-race-fix      Tue Nov 23 17:11:34 2004
 118 +++ 25-akpm/include/linux/quota.h       Tue Nov 23 17:11:34 2004
 119 @@ -286,6 +286,7 @@ struct quota_info {
 120         struct semaphore dqonoff_sem;           /* Serialize quotaon & quotaoff */
 121         struct rw_semaphore dqptr_sem;          /* serialize ops using quota_info struct, pointers from inode to dquots */
 122         struct inode *files[MAXQUOTAS];         /* inodes of quotafiles */
 123 +       struct vfsmount *mnt[MAXQUOTAS];        /* mountpoint entries of filesystems with quota files */
 124         struct mem_dqinfo info[MAXQUOTAS];      /* Information for each quota type */
 125         struct quota_format_ops *ops[MAXQUOTAS];        /* Operations for each type */
 126  };
 127 diff -puN include/linux/quotaops.h~quota-umount-race-fix include/linux/quotaops.h
 128 --- 25/include/linux/quotaops.h~quota-umount-race-fix   Tue Nov 23 17:11:34 2004
 129 +++ 25-akpm/include/linux/quotaops.h    Tue Nov 23 17:11:34 2004
 130 @@ -177,7 +177,7 @@ static __inline__ int DQUOT_OFF(struct s
 131  {
 132         int ret = -ENOSYS;
 133
 134 -       if (sb->s_qcop && sb->s_qcop->quota_off)
 135 +       if (sb_any_quota_enabled(sb) && sb->s_qcop && sb->s_qcop->quota_off)
 136                 ret = sb->s_qcop->quota_off(sb, -1);
 137         return ret;
 138  }
 139 _