On 01/13/2012 12:34 PM, Dave Chinner wrote:

On Thu, Jan 12, 2012 at 08:01:43PM -0700, Allison Henderson wrote:

quoted

Hi All,

I know this is an old topic, but I am poking it again because I've
had some work items wrap up, and Im planning on picking up on this
one again.  I am thinking about implementing extent locks to replace
i_mutex.  So I just wanted to touch base with folks and see what
people are working on because I know there were some folks out there
that were thing about doing similar solutions.

What locking API are you looking at? If you are looking at an
something like:

read_range_{try}lock(lock, off, len)
read_range_unlock(lock, off, len)
write_range_{try}lock(lock, off, len)
write_range_unlock(lock, off, len)

and implementing with an rbtree or a btree for tracking, then I
definitely have a use for it in XFS - replacing the current rwsem
that is used for the iolock. Range locks like this are the only
thing we need to allow concurrent buffered writes to the same file
to maintain the per-write exclusion that posix requires.

Interesting, so xfs already have these range lock, right? If yes, any
possibility that the code can be reused in ext4 since we have the same
thing in mind but don't have any resource to work on it by now.

btw, IIRC flock(2) uses a list to indicate the range lock, so if we can
make these pieces of codes common, at least there are 3 places that can
benefit from it. ;)

Thanks
Tao