4 files changed, 19 insertions, 1 deletions
diff --git a/src/internal/poll/copy_file_range_linux.go b/src/internal/poll/copy_file_range_linux.go
index fc34aef4cb..01b242a4ea 100644
--- a/src/internal/poll/copy_file_range_linux.go
+++ b/src/internal/poll/copy_file_range_linux.go
@@ -112,7 +112,15 @@ func CopyFileRange(dst, src *FD, remain int64) (written int64, handled bool, err
 			return 0, false, nil
 		case nil:
 			if n == 0 {
-				// src is at EOF, which means we are done.
+				// If we did not read any bytes at all,
+				// then this file may be in a file system
+				// where copy_file_range silently fails.
+				// https://lore.kernel.org/linux-fsdevel/20210126233840.GG4626@dread.disaster.area/T/#m05753578c7f7882f6e9ffe01f981bc223edef2b0
+				if written == 0 {
+					return 0, false, nil
+				}
+				// Otherwise src is at EOF, which means
+				// we are done.
 				return written, true, nil
 			}
 			remain -= n
diff --git a/src/internal/poll/sendfile_bsd.go b/src/internal/poll/sendfile_bsd.go
index a24e41dcaa..66005a9f5c 100644
--- a/src/internal/poll/sendfile_bsd.go
+++ b/src/internal/poll/sendfile_bsd.go
@@ -18,6 +18,10 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
 		return 0, err
 	}
 	defer dstFD.writeUnlock()
+	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
+		return 0, err
+	}
+
 	dst := int(dstFD.Sysfd)
 	var written int64
 	var err error
diff --git a/src/internal/poll/sendfile_linux.go b/src/internal/poll/sendfile_linux.go
index d64283007d..d6442e8666 100644
--- a/src/internal/poll/sendfile_linux.go
+++ b/src/internal/poll/sendfile_linux.go
@@ -16,6 +16,9 @@ func SendFile(dstFD *FD, src int, remain int64) (int64, error) {
 		return 0, err
 	}
 	defer dstFD.writeUnlock()
+	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
+		return 0, err
+	}
 
 	dst := int(dstFD.Sysfd)
 	var written int64
diff --git a/src/internal/poll/sendfile_solaris.go b/src/internal/poll/sendfile_solaris.go
index 762992e9eb..748c85131e 100644
--- a/src/internal/poll/sendfile_solaris.go
+++ b/src/internal/poll/sendfile_solaris.go
@@ -20,6 +20,9 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
 		return 0, err
 	}
 	defer dstFD.writeUnlock()
+	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
+		return 0, err
+	}
 
 	dst := int(dstFD.Sysfd)
 	var written int64