8c9e5e5e05
The way thin-pool right now is designed, user space is supposed to keep track of what device ids have already been used. If user space tries to create a new thin/snap device and device id has already been used, thin pool retuns -EEXIST. Upon receiving -EEXIST, current docker implementation simply tries the NextDeviceId++ and keeps on doing this till it finds a free device id. This approach has two issues. - It is little suboptimal. - If device id already exists, current kenrel implementation spits out a messsage on console. [17991.140135] device-mapper: thin: Creation of new snapshot 33 of device 3 failed. Here kenrel is trying to tell user that device id 33 has already been used. And this shows up for every device id docker tries till it reaches a point where device ids are not used. So if there are thousands of container and one is trying to create a new container after fresh docker start, expect thousands of such warnings to flood console. This patch saves the NextDeviceId in a file in /var/lib/docker/devmapper/metadata/deviceset-metadata and reads it back when docker starts. This way we don't retry lots of device ids which have already been used. There might be some device ids which are free but we will get back to them once device numbers wrap around (24bit limit on device ids). This patch should cut down on number of kernel warnings. Notice that I am creating a deviceset metadata file which is a global file for this pool. So down the line if we need to save more data we should be able to do that. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> |
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| .. | ||
| aufs | ||
| btrfs | ||
| devmapper | ||
| graphtest | ||
| vfs | ||
| driver.go | ||
| fsdiff.go | ||