Hi all, This patch series introduces a totally new filesystem summary counter online scrub feature. Whereas previous iterations froze the filesystem to count inodes and free blocks, this one drastically reduces overhead by loosening its precision somewhat. Instead of freezing the fs, we race the expected summary counter calculation with normal fs operations and use thresholding to check that the counters are in the ballpark, where ballpark means "off by less than 6% or so". The first patch implements a per-cpu counter of the number of blocks being held in delayed allocation reservations. This should represent the difference between the incore fdblocks counter and the one that would be recorded on disk if one were to iterate all the committed metadata structures. Patch #2 enables the scrub code to pause the posteof and cowblocks background reclamation workers temporarily to reduce perturbations in the summary counters while the scrubber runs. This isn't totally foolproof since they can be re-armed, but we only need ballpark correctness. Finally, patch #3 implements the actual fs summary counter scrubber code. If you're going to start using this mess, you probably ought to just pull from my git trees, which are linked below. This is an extraordinary way to destroy everything. Enjoy! Comments and questions are, as always, welcome. --D kernel git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-summary-counters xfsprogs git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-summary-counters
