On Tue, Nov 28, 2017 at 08:22:36PM +0100, David Sterba wrote: > On Tue, Nov 21, 2017 at 05:35:51PM -0700, Liu Bo wrote: > > If the underlying protocal doesn't support retry and there are some > > transient errors happening somewhere in our IO stack, we'd like to > > give an extra chance for IO. Or sometimes you see btrfs reporting > > 'wrr 1 flush 0 read 0 blabla' but the disk drive is 100% good, this > > retry may help a bit. > > A limited number of retries may make sense, though I saw some long > stalls after retries on bad disks. Tracking the retries would be a good > addition to the dev stats, ie. a soft error but still worth reporting. > > > In btrfs, read retry is handled in bio_readpage_error() with the retry > > unit being page size, for write retry however, we're going to do it in > > a different way, as a write may consist of several writes onto > > different stripes, retry write needs to be done right after the IO on > > each stripe completes and arrives at endio. > > > > Patch 1-3 are the implementation of retry write on error for > > non-raid56 profile. Patch 4-6 are for raid56 profile. Both raid56 > > and non-raid56 shares one retry function helper. > > > > Patch 3 does retry sector by sector, but since this patch set doesn't > > included badblocks support, patch 7 changes it back to retry the whole > > bio. (I didn't fold patch 7 to patch 3 in the hope of just reverting > > patch 7 once badblocks support is done, but I'm open to it.) > > What does 'badblocks' refer to? I know about the badblocks utility that > find and reportts bad blocks, possibly ext2 understands that and avoids > allocating them. Btrfs does not have such support.
The same thing, badblocks refers to block/badblocks.c, it derives from md's badblocks table, and now also serves as tracking bad cells in pmem. And yes, btrfs is yet to have that. Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
