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cgroupv1: don't ignore MemorySwap if Memory==-1 

Commit 18ebc51b3cc3 "Reset Swap when memory is set to unlimited (-1)"
added handling of the case when a user updates the container limits
to set memory to unlimited (-1) but do not set any other limits.
Apparently, in this case, if swap limit was previously set, kernel fails
to set memory.limit_in_bytes to -1 if memory.memsw.limit_in_bytes is
not set to -1.

What the above commit fails to handle correctly is the request when
Memory is set to -1 and MemorySwap is set to some specific limit N
(where N > 0). In this case, the value of N is silently discarded
and MemorySwap is set to -1 instead.

This is wrong thing to do, as the limit set, even if incorrectly,
should not be ignored.

Fix this by only assigning MemorySwap == -1 in case it was not
explicitly set.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2020-05-20 11:49:51 -07:00
parent 21cb2360b6
commit d57f5bb286
1 changed files with 3 additions and 3 deletions
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6
libcontainer/cgroups/fs/memory.go
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@ -74,9 +74,9 @@ func (s *MemoryGroup) Apply(d *cgroupData) (err error) {
} }
func setMemoryAndSwap(path string, cgroup *configs.Cgroup) error { func setMemoryAndSwap(path string, cgroup *configs.Cgroup) error {
// If the memory update is set to -1 we should also // If the memory update is set to -1 and the swap is not explicitly
// set swap to -1, it means unlimited memory. // set, we should also set swap to -1, it means unlimited memory.
if cgroup.Resources.Memory == -1 { if cgroup.Resources.Memory == -1 && cgroup.Resources.MemorySwap == 0 {
// Only set swap if it's enabled in kernel // Only set swap if it's enabled in kernel
if cgroups.PathExists(filepath.Join(path, cgroupMemorySwapLimit)) { if cgroups.PathExists(filepath.Join(path, cgroupMemorySwapLimit)) {
cgroup.Resources.MemorySwap = -1 cgroup.Resources.MemorySwap = -1