4fdc82012a
1. Use mount.Unmount() which ignores EINVAL ("not mounted") error,
and provides better error diagnostics (so we don't have to explicitly
add target to error messages).
2. Since we're ignoring "not mounted" error, we can call
multiple unmounts without any locking -- but since "auplink flush"
is still involved and can produce an error in logs, let's keep
the check for fs being mounted (it's just a statfs so should be fast).
2. While at it, improve the "can't unmount" error message in Put().
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 4beee98026feabe4f4f0468215b8fd9b56f90d5e)
Upstream-commit: 5b68d00abc4cad8b707a9a01dde9a420ca6eb995
Component: engine