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[4.8] fsmanager.GetStats performance regression #48

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kolyshkin wants to merge 2 commits into from
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[4.8] fsmanager.GetStats performance regression #48

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b303e56
libct/cg/fscommon.OpenFile: reverse checks order
kolyshkin Apr 27, 2021
2a0978d
libct/cg/fscommon.OpenFile: speed up ro case
kolyshkin Apr 27, 2021
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24 changes: 16 additions & 8 deletions libcontainer/cgroups/fscommon/open.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,12 +71,12 @@ func OpenFile(dir, file string, flags int) (*os.File, error) {
flags |= os.O_TRUNC | os.O_CREATE
mode = 0o600
}
if prepareOpenat2() != nil {
return openFallback(dir, file, flags, mode)
}
reldir := strings.TrimPrefix(dir, cgroupfsPrefix)
if len(reldir) == len(dir) { // non-standard path, old system?
return openWithSecureJoin(dir, file, flags, mode)
}
if prepareOpenat2() != nil {
return openWithSecureJoin(dir, file, flags, mode)
return openFallback(dir, file, flags, mode)
}

relname := reldir + "/" + file
Expand All @@ -93,10 +93,18 @@ func OpenFile(dir, file string, flags int) (*os.File, error) {
return os.NewFile(uintptr(fd), cgroupfsPrefix+relname), nil
}

func openWithSecureJoin(dir, file string, flags int, mode os.FileMode) (*os.File, error) {
path, err := securejoin.SecureJoin(dir, file)
if err != nil {
return nil, err
func openFallback(dir, file string, flags int, mode os.FileMode) (*os.File, error) {
var path string
// Do not use securejoin for files opened read-only,
// to speed up operations like GetStats.
if flags&unix.O_ACCMODE == unix.O_RDONLY {
path = dir + "/" + file
} else {
var err error
path, err = securejoin.SecureJoin(dir, file)
if err != nil {
return nil, err
}
}

return os.OpenFile(path, flags, mode)
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