From: Tom Clegg <tom@tomclegg.ca>
Date: Tue, 21 Jan 2020 16:34:57 +0000 (-0500)
Subject: 12308: Avoid returning partial reads before EOF.
X-Git-Tag: 2.1.0~297^2~13
X-Git-Url: https://git.arvados.org/arvados.git/commitdiff_plain/44ddbde1cd9945778ed7e4ae1d96c65e24f17742

12308: Avoid returning partial reads before EOF.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@tomclegg.ca>
---

diff --git a/lib/mount/fs.go b/lib/mount/fs.go
index 5b6fc0012f..774948f574 100644
--- a/lib/mount/fs.go
+++ b/lib/mount/fs.go
@@ -320,6 +320,16 @@ func (fs *keepFS) Read(path string, buf []byte, ofst int64, fh uint64) (n int) {
 		return fs.errCode(err)
 	}
 	n, err := f.Read(buf)
+	for err == nil && n < len(buf) {
+		// f is an io.Reader ("If some data is available but
+		// not len(p) bytes, Read conventionally returns what
+		// is available instead of waiting for more") -- but
+		// our caller requires us to either fill buf or reach
+		// EOF.
+		done := n
+		n, err = f.Read(buf[done:])
+		n += done
+	}
 	if err != nil && err != io.EOF {
 		log.Printf("error reading %q: %s", path, err)
 		return fs.errCode(err)