On Mon, Dec 03, 2012 at 05:42:22PM -0600, Mark Tinguely wrote: > From: Dave Chinner <[email protected]> > > Upstream commit: 507630b29f13a3d8689895618b12015308402e22 > > For the direct IO write path, we only really need the ilock to be taken in > exclusive mode during IO submission if we need to do extent allocation > instead of all the time. > > Change the block mapping code to take the ilock in shared mode for the > initial block mapping, and only retake it exclusively when we actually > have to perform extent allocations. We were already dropping the ilock > for the transaction allocation, so this doesn't introduce new race windows. >
I'm nervous about changing locking like this in -stable kernels. It's a performance optimisation, not a bug fix, and it wasn't a problem that xfstests uncovered. Also, xfstests doesn't really stress the correctness of this code, which is another reason I'm nervous about it.... Cheers, Dave. -- Dave Chinner [email protected] -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
