From: Loic Dachary <loic@dachary.org>
Date: Fri, 28 Feb 2014 12:57:20 +0000 (+0100)
Subject: osd: do not attempt to read past the object size
X-Git-Tag: v0.78~105^2~4
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=927153f5c7ffd8d5f0a4a9a770f68aa9d2021c9f;p=ceph.git

osd: do not attempt to read past the object size

When reading from a replicated pool, trying to read more than the object
size results in a short read that does not go beyond the object size. In
erasure coded pools, objects are padded and the read will return more
bytes than the object actually contains.

http://tracker.ceph.com/issues/7423 fixes #7423

Signed-off-by: Loic Dachary <loic@dachary.org>
---

diff --git a/src/osd/ReplicatedPG.cc b/src/osd/ReplicatedPG.cc
index 2b64b481b5b1..e537abe00658 100644
--- a/src/osd/ReplicatedPG.cc
+++ b/src/osd/ReplicatedPG.cc
@@ -2915,24 +2915,28 @@ int ReplicatedPG::do_osd_ops(OpContext *ctx, vector<OSDOp>& ops)
     case CEPH_OSD_OP_READ:
       ++ctx->num_read;
       {
-	uint64_t trim = (uint64_t)-1;
 	__u32 seq = oi.truncate_seq;
+	uint64_t size = oi.size;
+	bool trimmed_read = false;
 	// are we beyond truncate_size?
 	if ( (seq < op.extent.truncate_seq) &&
-	     (op.extent.offset + op.extent.length > op.extent.truncate_size) ) {
-
-	  // truncated portion of the read
-	  uint64_t from = MAX(op.extent.offset, op.extent.truncate_size);  // also end of data
-	  uint64_t to = op.extent.offset + op.extent.length;
-	  trim = to - from;
-
-	  op.extent.length = op.extent.length - trim;
+	     (op.extent.offset + op.extent.length > op.extent.truncate_size) )
+	  size = op.extent.truncate_size;
+
+	if (op.extent.offset >= size) {
+	  op.extent.length = 0;
+	  trimmed_read = true;
+	} else if (op.extent.offset + op.extent.length > size) {
+	  op.extent.length = size - op.extent.offset;
+	  trimmed_read = true;
 	}
 
 	// read into a buffer
 	bufferlist bl;
-	if (trim != (uint64_t)-1 && op.extent.length == 0) {
-	  // read size was trimmed to zero
+	if (trimmed_read && op.extent.length == 0) {
+	  // read size was trimmed to zero and it is expected to do nothing
+	  // a read operation of 0 bytes does *not* do nothing, this is why
+	  // the trimmed_read boolean is needed
 	} else if (pool.info.require_rollback()) {
 	  ctx->pending_async_reads.push_back(
 	    make_pair(