Prefaulting for i/o buffers

[Gleb Kurtsou]

On (01/03/2012 09:10), Christoph Hellwig wrote:
> On Thu, Mar 01, 2012 at 01:16:24PM +0200, Gleb Kurtsou wrote:
> > Are you aware of a real "libraries for file systems" VFS example? It
> > sounds very interesting but I'm afraid it's going to look good only in
> > theory. E.g. locking at file system level (Darwin, Dragonfly BSD) looks
> > rather messy (IMHO) and more likely to be bug prone. On the other side
> > Linux has optional per file system rename lock making VOP_RENAME
> > implementation much easier, while ours is tremendously difficult to do
> > right.
> 
> All namespace locking in Linux is in the VFS, and it mandatory.  A
> filesystem wide lock is only used for cross-directory renames.
> 
> A more detailed description is here:
> 
> 	http://git.kernel.dk/?p=linux.git;a=blob;f=Documentation/filesystems/directory-locking
> 

My bad. I thought s_vfs_rename_mutex can be optional. Quite unfortunate
linux doesn't support concurrent cross-directory renames :)

Thanks,
Gleb.