Commits on Jan 17, 2013

1. Fix 'zfs rollback' on mounted file systems …

   Rolling back a mounted filesystem with open file handles and
   cached dentries+inodes never worked properly in ZoL.  The
   major issue was that Linux provides no easy mechanism for
   modules to invalidate the inode cache for a file system.
   
   Because of this it was possible that an inode from the previous
   filesystem would not get properly dropped from the cache during
   rolling back.  Then a new inode with the same inode number would
   be create and collide with the existing cached inode.  Ideally
   this would trigger an VERIFY() but in practice the error wasn't
   handled and it would just NULL reference.
   
   Luckily, this issue can be resolved by sprucing up the existing
   Solaris zfs_rezget() functionality for the Linux VFS.
   
   The way it works now is that when a file system is rolled back
   all the cached inodes will be traversed and refetched from disk.
   If a version of the cached inode exists on disk the in-core
   copy will be updated accordingly.  If there is no match for that
   object on disk it will be unhashed from the inode cache and
   marked as stale.
   
   This will effectively make the inode unfindable for lookups
   allowing the inode number to be immediately recycled.  The inode
   will then only be accessible from the cached dentries.  Subsequent
   dentry lookups which reference a stale inode will result in the
   dentry being invalidated.  Once invalidated the dentry will drop
   its reference on the inode allowing it to be safely pruned from
   the cache.
   
   Special care is taken for negative dentries since they do not
   reference any inode.  These dentires will be invalidate based
   on when they were added to the dentry cache.  Entries added
   before the last rollback will be invalidate to prevent them
   from masking real files in the dataset.
   
   Two nice side effects of this fix are:
   
   * Removes the dependency on spl_invalidate_inodes(), it can now
     be safely removed from the SPL when we choose to do so.
   
   * zfs_znode_alloc() no longer requires a dentry to be passed.
     This effectively reverts this portition of the code to its
     upstream counterpart.  The dentry is not instantiated more
     correctly in the Linux ZPL layer.
   
   Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
   Issue openzfs#795

   

   behlendorf committed Jan 17, 2013
   Configuration menu

   • View commit details
   • Copy full SHA for 7a71ff5
   • Browse repository at this point

   Copy the full SHA

   7a71ff5 View commit details

   Browse the repository at this point in the history