Here's my situation: I currently have a Macbook running OS X El Capitan. Prior to my upgrade to El Capitan, while running Yosemite, I had two partitions of my hard drive: one for my base Yosemite install and one that I was using to test El Capitan (the Beta version). After I upgraded to the GA version of El Capitan earlier this week, I deleted the old partition of the Beta version. That was fine. Now, however, I have an unused ~120 GB of space formerly allocated to that partition. So, I attempt to use the new Disk Utility to resize my partition to get that space back.
I'm able to drag the control so that now it says my device will have the full 480 GB size. I click Apply. The utility starts to do the resize, and then...fails:
Checking extended attribute files. Checking volume bitmap. Checking volume information. File system check exit code is 8. File system verify or repair failed. Operation failed...