On Thu, Sep 15, 2016 at 11:36:14AM +0200, Marcin Mirosław wrote:

Hi!
I was playing with fs without tiering. I was using it for tmp dir for
compilation. Next I changed in sys:
echo crc64 > options/data_checksum
echo crc64 > options/metadata_checksum
echo crc64 > options/str_hash

After a couple of minutes I got:
[ 8372.574346] bcache (dm-10): IO error on dm-10 for checksum error
[ 8372.680196] bcache (dm-10): IO error on dm-10 for checksum error
[ 8464.361860] bcache (dm-10): IO error on dm-10 for checksum error
[ 8466.146966] bcache (dm-10): IO error on dm-10 for checksum error
[ 8466.995095] bcache (dm-10): IO error on dm-10 for checksum error
[ 8469.199749] bcache (dm-10): IO error on dm-10 for checksum error
[ 8469.441408] bcache (dm-10): IO error on dm-10 for checksum error
[ 8469.722676] bcache (dm-10): IO error on dm-10 for checksum error
[ 8469.827055] bcache (dm-10): IO error on dm-10 for checksum error
[ 8470.038869] bcache (dm-10): IO error on dm-10 for checksum error
[ 8470.236663] bcache (dm-10): IO error on dm-10 for checksum error
[ 8470.427094] bcache (dm-10): IO error on dm-10 for checksum error
[ 8472.030519] bcache (dm-10): IO error on dm-10 for checksum error
[ 8473.098820] bcache (dm-10): IO error on dm-10 for checksum error
[ 8916.491297] bcache (dm-10): IO error on dm-10 for checksum error
[ 8916.715057] bcache (dm-10): IO error on dm-10 for checksum error
[ 8916.715111] bcache (dm-10): too many IO errors on dm-10, setting
filesystem RO
[ 8916.733056] bcache (dm-10): IO error on dm-10 for checksum error
[ 8916.733125] bcache (dm-10): dm-10 read only
[ 8916.733161] bcache (dm-10): too many IO errors on dm-10, setting
device RO
[ 8916.988286] bcache (dm-10): IO error: read only
[ 8916.988545] bcache (dm-10): IO error: read only

Ok, it turns out the crc64 for data checksums code was just fubar. Fix is up
(the fix does change how crc64 is computed for bios though, so it'll be
incompatible with your existing filesystem).

Also pushed a patch that adds some more error messages to fs-gc, we should
figure out why it wouldn't mount. I can't think of any reason why data checksum
errors would've caused that.