I've recently setup a system (Kernel 3.12.5-1-ARCH) which is layered as follows: /dev/sdb3 - cache0 (80 GB Intel SSD) /dev/sdc1 - backing device (2 TB WD HDD) sdb3+sdc1 => /dev/bcache0 On /dev/bcache0, there's a btrfs filesystem with 2 subvolumes, mounted as / and /home. What's been bothering me are the following entries in my kernel log: [13811.845540] incomplete page write in btrfs with offset 1536 and length 2560 [13870.326639] incomplete page write in btrfs with offset 3072 and length 1024 The offset/length values are always either 1536/2560 or 3072/1024, they sum up nicely to 4K. There are 607 of those in there as I am writing this (well, 651 now :)), the machine has been up 18 hours and been under no particular I/O strain (it's a desktop). Trying to fix this, I unattached the cache (still using /dev/bcache0, but without /dev/sdb3 attached), causing these errors to disappear. As soon as I re-attached /dev/sdb3 they started again, so I am fairly sure it's an unfavorable interaction between bcache and btrfs. Is this something I should be worried about (they're only emitted with KERN_INFO) or just an alignment problem? The underlying HDD is using 4K-Sectors, while the block_size of bcache seems to be 512, could that be the issue here? I've also encountered incomplete reads and a few csum errors, but I have not been able to trigger these regularly. Any advice is appreciated, - eb PS: I've only sent this to the bcache list so far, if this is a concern for btrfs, let me know and I will take it there. However, without the cache enabled, it seems to run without a hitch. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
