cmd/link: ignore "operation not permitted" fallocate errors.

Ignore an additional class of errors form fallocate, falling back to
heap allocated buffers for output.

Fixes #41356

Change-Id: Iaaa91620cec644c78978e0b258f166bc204a3f85
Reviewed-on: https://go-review.googlesource.com/c/go/+/254777
Trust: Jeremy Faller <[email protected]>
Run-TryBot: Jeremy Faller <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>

Author: jeremyfaller

src/cmd/link/internal/ld/outbuf.go

@@ -13,11 +13,10 @@ import (
 	"os"
 )
 
-// If fallocate is not supported on this platform, return this error.
-// Note this is the same error returned by filesystems that don't support
-// fallocate, and that is intentional. The error is ignored where needed, and
-// OutBuf writes to heap memory.
-const fallocateNotSupportedErr = "operation not supported"
+// If fallocate is not supported on this platform, return this error. The error
+// is ignored where needed, and OutBuf writes to heap memory.
+var errNoFallocate = errors.New("operation not supported")
+
 const outbufMode = 0775
 
 // OutBuf is a buffered file writer.

src/cmd/link/internal/ld/outbuf_mmap.go

@@ -28,7 +28,7 @@ func (out *OutBuf) Mmap(filesize uint64) (err error) {
 		// Some file systems do not support fallocate. We ignore that error as linking
 		// can still take place, but you might SIGBUS when you write to the mmapped
 		// area.
-		if err.Error() != fallocateNotSupportedErr {
+		if err != syscall.ENOTSUP && err != syscall.EPERM && err != errNoFallocate {
 			return err
 		}
 	}

src/cmd/link/internal/ld/outbuf_nofallocate.go

@@ -6,8 +6,6 @@
 
 package ld
 
-import "errors"
-
 func (out *OutBuf) fallocate(size uint64) error {
-	return errors.New(fallocateNotSupportedErr)
+	return errNoFallocate
 }