From b72a13ef1fcde577edd5ed397e924178ca083f9b Mon Sep 17 00:00:00 2001
From: Alex Ainscow <aainscow@uk.ibm.com>
Date: Thu, 17 Apr 2025 22:53:31 +0100
Subject: [PATCH] osd: Fix panic on fast_read completion in optimised EC

The completion of sub reads was incorrectly marking all processed reads complete on the first read.

This was causing an early attempt at reconstruct, which panics.

Signed-off-by: Alex Ainscow <aainscow@uk.ibm.com>
---
 src/osd/ECBackend.cc | 45 ++++++++++++++++++--------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/src/osd/ECBackend.cc b/src/osd/ECBackend.cc
index 05e34602097c4..7c8781b3e6111 100644
--- a/src/osd/ECBackend.cc
+++ b/src/osd/ECBackend.cc
@@ -1227,20 +1227,10 @@ void ECBackend::handle_sub_read_reply(
       rop.complete.emplace(hoid, &sinfo);
     }
     auto &complete = rop.complete.at(hoid);
-    for (auto &&[shard, read]: std::as_const(req.shard_reads)) {
-      if (complete.errors.contains(read.pg_shard)) continue;
-
-      complete.processed_read_requests[shard].union_of(read.extents);
-
-      if (!rop.complete.contains(hoid) ||
-        !complete.buffers_read.contains(shard)) {
-        if (!read.extents.empty()) continue; // Complete the actual read first.
-
-        // If we are first here, populate the completion.
-        if (!rop.complete.contains(hoid)) {
-          rop.complete.emplace(hoid, read_result_t(&sinfo));
-        }
-      }
+    const shard_read_t &read = req.shard_reads.at(from.shard);
+    if (!complete.errors.contains(from)) {
+      dout(20) << __func__ <<" read:" << read << dendl;
+      complete.processed_read_requests[from.shard].union_of(read.extents);
     }
   }
   for (auto &&[hoid, attr]: op.attrs_read) {
@@ -1307,7 +1297,7 @@ void ECBackend::handle_sub_read_reply(
               // We found that new reads are required to do a decode.
               need_resend = true;
               continue;
-            } else if (r >  0) {
+            } else if (r > 0) {
               // No new reads were requested. This means that some parity
               // shards can be assumed to be zeros.
               err = 0;
@@ -1342,7 +1332,8 @@ void ECBackend::handle_sub_read_reply(
             rop.complete.at(oid).errors.clear();
           }
         }
-        // avoid re-read for completed object as we may send remaining reads for uncopmpleted objects
+        // avoid re-read for completed object as we may send remaining reads for
+        // uncompleted objects
         rop.to_read.at(oid).shard_reads.clear();
         rop.to_read.at(oid).want_attrs = false;
         ++is_complete;
@@ -1601,21 +1592,21 @@ void ECBackend::submit_transaction(
 }
 
 int ECBackend::objects_read_sync(
-  const hobject_t &hoid,
-  uint64_t off,
-  uint64_t len,
-  uint32_t op_flags,
-  bufferlist *bl) {
+    const hobject_t &hoid,
+    uint64_t off,
+    uint64_t len,
+    uint32_t op_flags,
+    bufferlist *bl) {
   return -EOPNOTSUPP;
 }
 
 void ECBackend::objects_read_async(
-  const hobject_t &hoid,
-  uint64_t object_size,
-  const list<pair<ec_align_t,
-                  pair<bufferlist*, Context*>>> &to_read,
-  Context *on_complete,
-  bool fast_read) {
+    const hobject_t &hoid,
+    uint64_t object_size,
+    const list<pair<ec_align_t,
+                    pair<bufferlist*, Context*>>> &to_read,
+    Context *on_complete,
+    bool fast_read) {
   map<hobject_t, std::list<ec_align_t>> reads;
 
   uint32_t flags = 0;
-- 
2.39.5