diff options
-rw-r--r-- | src/internal/poll/copy_file_range_linux.go | 50 |
1 files changed, 48 insertions, 2 deletions
diff --git a/src/internal/poll/copy_file_range_linux.go b/src/internal/poll/copy_file_range_linux.go index 24bee614a6..fc34aef4cb 100644 --- a/src/internal/poll/copy_file_range_linux.go +++ b/src/internal/poll/copy_file_range_linux.go @@ -10,15 +10,61 @@ import ( "syscall" ) -var copyFileRangeSupported int32 = 1 // accessed atomically +var copyFileRangeSupported int32 = -1 // accessed atomically const maxCopyFileRangeRound = 1 << 30 +func kernelVersion() (major int, minor int) { + var uname syscall.Utsname + if err := syscall.Uname(&uname); err != nil { + return + } + + rl := uname.Release + var values [2]int + vi := 0 + value := 0 + for _, c := range rl { + if '0' <= c && c <= '9' { + value = (value * 10) + int(c-'0') + } else { + // Note that we're assuming N.N.N here. If we see anything else we are likely to + // mis-parse it. + values[vi] = value + vi++ + if vi >= len(values) { + break + } + value = 0 + } + } + switch vi { + case 0: + return 0, 0 + case 1: + return values[0], 0 + case 2: + return values[0], values[1] + } + return +} + // CopyFileRange copies at most remain bytes of data from src to dst, using // the copy_file_range system call. dst and src must refer to regular files. func CopyFileRange(dst, src *FD, remain int64) (written int64, handled bool, err error) { - if atomic.LoadInt32(©FileRangeSupported) == 0 { + if supported := atomic.LoadInt32(©FileRangeSupported); supported == 0 { return 0, false, nil + } else if supported == -1 { + major, minor := kernelVersion() + if major > 5 || (major == 5 && minor >= 3) { + atomic.StoreInt32(©FileRangeSupported, 1) + } else { + // copy_file_range(2) is broken in various ways on kernels older than 5.3, + // see issue #42400 and + // https://man7.org/linux/man-pages/man2/copy_file_range.2.html#VERSIONS + atomic.StoreInt32(©FileRangeSupported, 0) + return 0, false, nil + } } for remain > 0 { max := remain |