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Use strings.Cut where possible #4470

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Use strings.Cut where possible #4470

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0e2d611
exec: use strings.Cut to parse --cgroup
kolyshkin Oct 23, 2024
d9e1005
libct/cg/fs: getPercpuUsage: rm TODO
kolyshkin Oct 23, 2024
a8da6c6
libct/cg/fs: refactor getCpusetStat
kolyshkin Oct 23, 2024
a4ed2d8
libcontainer/cgroups/fs: some refactoring
kolyshkin Oct 23, 2024
32fa40a
libct/cg/fs2: simplify parseCgroupFromReader
kolyshkin Oct 23, 2024
486c451
libct/cg/fs2: use strings.Cut in setUnified
kolyshkin Oct 23, 2024
b33fe69
libct/cg/fs2: use strings.Cut in parsePSIData
kolyshkin Oct 23, 2024
4c86035
libct/cg/fscommon: use strings.Cut in RDMA parser
kolyshkin Oct 23, 2024
cddca40
libct/cg/fscommon: use strings.Cut
kolyshkin Oct 23, 2024
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17 changes: 7 additions & 10 deletions exec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -124,20 +124,17 @@ func getSubCgroupPaths(args []string) (map[string]string, error) {
paths := make(map[string]string, len(args))
for _, c := range args {
// Split into controller:path.
cs := strings.SplitN(c, ":", 3)
if len(cs) > 2 {
return nil, fmt.Errorf("invalid --cgroup argument: %s", c)
}
if len(cs) == 1 { // no controller: prefix
if ctr, path, ok := strings.Cut(c, ":"); ok {
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@lifubang lifubang Dec 20, 2024 •
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I havn't checked that whether this will lead to some regressions or not, for example, if c == "a:b:c:d:e":
When using SplitN, cs[1] will be "b";
When using Cut, path will be "b:c:d:e".

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So, the old code would error out when c == "a:b:c:d:e".

The new code would not, assigning b:c:d:e to path.

To me, the new code is (ever so slightly) more correct, since : is a valid symbol which should be allowed in path.

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Yup, was looking at that as well; agreed, looks like new code is more correct here.

I still need to have a quick look at the splitting on commas, and the if len(args) != 1 { check below. Probably will check out this branch locally

// There may be a few comma-separated controllers.
for _, ctrl := range strings.Split(ctr, ",") {
paths[ctrl] = path
}
} else {
// No controller: prefix.
if len(args) != 1 {
return nil, fmt.Errorf("invalid --cgroup argument: %s (missing <controller>: prefix)", c)
}
paths[""] = c
Comment on lines +133 to 137
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Was trying to somewhat grasp what this case is for;

  • if zero args are passed, we return early (start of function)
  • if 1 arg is passed, it MUST have a controller prefix
  • But if 2 (or more) args are passed, then we don't have to?

So;

# valid: single arg
--cgroup a,b:/hello-world

# valid: single arg without controller
--cgroup /hello-world

# invalid: multiple args, one without controller
--cgroup a,b:/hello-world --cgroup /hello-world
--cgroup /hello-world --cgroup a,b:/hello-world

So, if no controller is passed, it's for everything which is only allowed if no other (per-controller) paths are specified, correct? (so not allowed to be combined).

☝️ Perhaps that's something we should capture in a comment on the function

Also;

  • perhaps we need to change the ok check to also check if controller is not empty, or is ,,,,,:/hello-world something that should be considered valid?
  • are duplicate controllers valid? They currently overwrite previous values (foo,foo,foo:/bar, foo:/baz)

} else {
// There may be a few comma-separated controllers.
for _, ctrl := range strings.Split(cs[0], ",") {
paths[ctrl] = cs[1]
}
}
}
return paths, nil
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