On Wed, Dec 15, 2021 at 05:09:48PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > Ian Kent reported that for inline symlinks, it's possible for > vfs_readlink to hang on to the target buffer returned by > _vn_get_link_inline long after it's been freed by xfs inode reclaim. > This is a layering violation -- we should never expose XFS internals to > the VFS. > > When the symlink has a remote target, we allocate a separate buffer, > copy the internal information, and let the VFS manage the new buffer's > lifetime. Let's adapt the inline code paths to do this too. It's > less efficient, but fixes the layering violation and avoids the need to > adapt the if_data lifetime to rcu rules. Clearly I don't care about > readlink benchmarks. > > As a side note, this fixes the minor locking violation where we can > access the inode data fork without taking any locks; proper locking (and > eliminating the possibility of having to switch inode_operations on a > live inode) is essential to online repair coordinating repairs > correctly. > > Reported-by: Ian Kent <raven@xxxxxxxxxx> > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> Looks fine, nicely avoids all the nasty RCU interactions trying to handle this after the fact. Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx
