Re: [PATCH 1/2] locks: introduce i_blockleases to close lease races

On Mon, Jun 13, 2011 at 04:37:03PM -0400, Mimi Zohar wrote:

On Mon, 2011-06-13 at 08:19 -0400, J. Bruce Fields wrote:

quoted

On Sun, Jun 12, 2011 at 04:54:33PM -0400, Mimi Zohar wrote:

quoted

On Sun, 2011-06-12 at 15:12 -0400, J. Bruce Fields wrote: 

quoted

On Sun, Jun 12, 2011 at 03:10:04PM -0400, Mimi Zohar wrote:

quoted

In lieu of adding a new inode field, another possible option, a bit
kludgy, would be extending i_flock with an additional fl_flag
FL_BLOCKLEASE.

#define IS_BLOCKLEASE(fl)    (fl->fl_flags & FL_BLOCKLEASE)

Alas, that would mean adding and removing one of these file locks around
every single link, unlink, rename,....

--b.

You're adding a call to break_lease() for each of them.  Currently
__break_lease() is only called if a lease exists. Assuming there aren't
any existing leases, couldn't break_lease() call something like
block_lease()?  The free would be after the link, unlink, ...,
completed/failed.

(You wouldn't actually need to alloc/free the 'struct file_lock' each
time, just set the pointer and reset to NULL.)

Well, the pointer has to be set to something.  I suppose we could put a
struct file_lock on the stack.

--b.

Instead of putting the struct file_lock on the stack, how about creating
a dummy list containing a single element with FL_BLOCKLEASE set?

I'm afraid I don't understand what you're proposing.  Could you explain
in more detail?

--b.