From: Sage Weil <sage@inktank.com>
Date: Mon, 17 Jun 2013 02:48:52 +0000 (-0700)
Subject: client: fix sync read zeroing at EOF
X-Git-Tag: v0.66~60
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=ee40c217e373b538e227f7218b09c1c794b4124a;p=ceph.git

client: fix sync read zeroing at EOF

If we have a read that hits EOF, we need to do a short read.  Previously
we would zero the buffer if we were completely withing the file, but
we also need to zero things if we overlap with EOF.  This fixes a hang
of mpi-fsx on ceph-fuse.  Triggered/tested by
LibCephFS.MulticlientHoleEOF.

Fixes: #5368
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
---

diff --git a/src/client/Client.cc b/src/client/Client.cc
index 204dc98d74d0..dec364567b62 100644
--- a/src/client/Client.cc
+++ b/src/client/Client.cc
@@ -5826,13 +5826,17 @@ int Client::_read_sync(Fh *f, uint64_t off, uint64_t len, bufferlist *bl)
     }
     // short read?
     if (r >= 0 && r < wanted) {
-      if (pos + left <= in->size) {
-	// hole, zero and return.
-	bufferptr z(left);
+      if (pos < in->size) {
+	// zero up to known EOF
+	int some = MIN(in->size - pos, left);
+	bufferptr z(some);
 	z.zero();
 	bl->push_back(z);
-	read += left;
-	return read;
+	read += some;
+	pos += some;
+	left -= some;
+	if (left == 0)
+	  return read;
       }
 
       // reverify size