On Fri, Mar 22, 2013 at 11:27:16PM -0400, Mike Snitzer wrote: > On Fri, Mar 22 2013 at 7:16pm -0400, > Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > > > On Fri, Mar 22, 2013 at 06:34:28PM -0400, Mike Snitzer wrote: > > > On Fri, Mar 22 2013 at 4:11pm -0400, > > > Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > > > > > > > The new writethrough strategy for dm-cache issues a bio to the origin device, > > > > remaps the bio to the cache device, and issues the bio to the cache device. > > > > However, the block layer modifies bi_sector and bi_size, so we need to preserve > > > > these or else nothing gets written to the cache (bi_size == 0). This fixes the > > > > problem where someone writes a block through the cache, but a subsequent reread > > > > (from the cache) returns old contents. > > > > > > Your writethrough blkid test results are certainly strange. But I'm not > > > aware of where the block layer would modify bi_size and bi_sector; > > > please elaborate. > > > > > > I cannot reproduce your original report. I developed > > > 'test_writethrough_ext4_uuids_match', apologies for the ruby code: > > > > Hmm... I'm building my kernels off 0a7e453103b9718d357688b83bb968ee108cc874 in > > Linus' tree (post 3.9-rc3). This is the full output of dmsetup table: > > > > moocache-blocks: 0 1039360 linear 8:16 9088 > > moocache-metadata: 0 8704 linear 8:16 384 > > moocache: 0 67108864 cache 253:0 253:1 8:0 512 1 writethrough default 4 random_threshold 4 sequential_threshold 32768 > > > > 253:0 -> moocache-metadata and 253:1 -> moocache-blocks. > > > > I'm curious what your setup is... > > Here are the tables: > test-dev-238267: 0 8192 linear /dev/stec/metadata 0 > test-dev-255913: 0 2097152 linear /dev/stec/metadata 8192 > test-dev-655144: 0 20480 linear /dev/spindle/data 0 > 0 20480 cache /dev/mapper/test-dev-238267 /dev/mapper/test-dev-255913 /dev/mapper/test-dev-655144 512 1 writethrough default 0 > > And I tweaked 'test_writethrough_ext4_uuids_match' to make sure to use the > same thresholds you're using, full status output: > 0 20480 cache 15/1024 0 19 0 0 0 0 0 0 1 writethrough 2 migration_threshold 32768 4 random_threshold 4 sequential_threshold 512 > > So the big difference is the thinp-test-suite uses intermediate linear > DM layers above the slower sd device (spindle/data) -- whereas in your > setup the origin device is direct to sd (8:0). > > I'll re-run with the origin directly on sd in the morning and will > report back. Interesting ... if I set up this: # echo "0 67108864 linear /dev/sda 0" | dmsetup create origin And then repeat the test, but using /dev/mapper/origin as the origin instead of /dev/sda, the problem goes away. --D -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
