From b36350b804edac0b4a0d8450292f51dc73a3986a Mon Sep 17 00:00:00 2001
From: Konstantin Knizhnik <knizhnik@neon.tech>
Date: Wed, 5 Feb 2025 17:47:53 +0200
Subject: [PATCH] Fix bugs in lfc_cache_containsv

---
 pgxn/neon/file_cache.c     | 51 +++++++++++++++++---------------------
 pgxn/neon/pagestore_smgr.c |  9 ++++---
 2 files changed, 29 insertions(+), 31 deletions(-)

diff --git a/pgxn/neon/file_cache.c b/pgxn/neon/file_cache.c
index 08b7652175..b8e27b2aa0 100644
--- a/pgxn/neon/file_cache.c
+++ b/pgxn/neon/file_cache.c
@@ -220,10 +220,8 @@ lfc_maybe_disabled(void)
 static bool
 lfc_ensure_opened(void)
 {
-	bool		enabled = !lfc_maybe_disabled();
-
 	/* Open cache file if not done yet */
-	if (lfc_desc <= 0 && enabled)
+	if (lfc_desc <= 0)
 	{
 		lfc_desc = BasicOpenFile(lfc_path, O_RDWR);
 
@@ -233,7 +231,7 @@ lfc_ensure_opened(void)
 			return false;
 		}
 	}
-	return enabled;
+	return true;
 }
 
 static void
@@ -509,47 +507,44 @@ lfc_cache_containsv(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
 
 	CriticalAssert(BufTagGetRelNumber(&tag) != InvalidRelFileNumber);
 
-	tag.blockNum = (blkno + i) & ~(BLOCKS_PER_CHUNK - 1);
+	tag.blockNum = blkno & ~(BLOCKS_PER_CHUNK - 1);
 	hash = get_hash_value(lfc_hash, &tag);
-	chunk_offs = (blkno + i) & (BLOCKS_PER_CHUNK - 1);
+	chunk_offs = blkno & (BLOCKS_PER_CHUNK - 1);
 
 	LWLockAcquire(lfc_lock, LW_SHARED);
 
+	if (!LFC_ENABLED())
+	{
+		LWLockRelease(lfc_lock);
+		return 0;
+	}
 	while (true)
 	{
-		int		this_chunk = Min(nblocks, BLOCKS_PER_CHUNK - chunk_offs);
-		if (LFC_ENABLED())
-		{
-			entry = hash_search_with_hash_value(lfc_hash, &tag, hash, HASH_FIND, NULL);
+		int		this_chunk = Min(nblocks - i, BLOCKS_PER_CHUNK - chunk_offs);
+		entry = hash_search_with_hash_value(lfc_hash, &tag, hash, HASH_FIND, NULL);
 
-			if (entry != NULL)
+		if (entry != NULL)
+		{
+			for (; chunk_offs < BLOCKS_PER_CHUNK && i < nblocks; chunk_offs++, i++)
 			{
-				for (; chunk_offs < BLOCKS_PER_CHUNK && i < nblocks; chunk_offs++, i++)
+				if ((entry->bitmap[chunk_offs >> 5] & 
+					 ((uint32)1 << (chunk_offs & 31))) != 0)
 				{
-					if ((entry->bitmap[chunk_offs >> 5] & 
-						((uint32)1 << (chunk_offs & 31))) != 0)
-					{
-						BITMAP_SET(bitmap, i);
-						found++;
-					}
+					BITMAP_SET(bitmap, i);
+					found++;
 				}
 			}
-			else
-			{
-				i += this_chunk;
-			}
 		}
 		else
 		{
-			LWLockRelease(lfc_lock);
-			return found;
+			i += this_chunk;
 		}
 
 		/*
 		 * Break out of the iteration before doing expensive stuff for
 		 * a next iteration
 		 */
-		if (i + 1 >= nblocks)
+		if (i >= nblocks)
 			break;
 
 		/*
@@ -563,8 +558,8 @@ lfc_cache_containsv(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
 
 	LWLockRelease(lfc_lock);
 
-#if USE_ASSERT_CHECKING
-	do {
+#ifdef USE_ASSERT_CHECKING
+	{
 		int count = 0;
 
 		for (int j = 0; j < nblocks; j++)
@@ -574,7 +569,7 @@ lfc_cache_containsv(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
 		}
 
 		Assert(count == found);
-	} while (false);
+	}
 #endif
 
 	return found;
diff --git a/pgxn/neon/pagestore_smgr.c b/pgxn/neon/pagestore_smgr.c
index 54cacea984..0206c63b53 100644
--- a/pgxn/neon/pagestore_smgr.c
+++ b/pgxn/neon/pagestore_smgr.c
@@ -363,6 +363,7 @@ compact_prefetch_buffers(void)
 		target_slot->buftag = source_slot->buftag;
 		target_slot->shard_no = source_slot->shard_no;
 		target_slot->status = source_slot->status;
+		target_slot->flags = source_slot->flags;
 		target_slot->response = source_slot->response;
 		target_slot->reqid = source_slot->reqid;
 		target_slot->request_lsns = source_slot->request_lsns;
@@ -916,7 +917,7 @@ prefetch_register_bufferv(BufferTag tag, neon_request_lsns *frlsns,
 {
 	uint64		min_ring_index;
 	PrefetchRequest hashkey;
-#if USE_ASSERT_CHECKING
+#ifdef USE_ASSERT_CHECKING
 	bool		any_hits = false;
 #endif
 	/* We will never read further ahead than our buffer can store. */
@@ -955,7 +956,7 @@ Retry:
 		else
 			lsns = NULL;
 
-#if USE_ASSERT_CHECKING
+#ifdef USE_ASSERT_CHECKING
 		any_hits = true;
 #endif
 
@@ -1117,6 +1118,7 @@ Retry:
 		slot->buftag = hashkey.buftag;
 		slot->shard_no = get_shard_number(&tag);
 		slot->my_ring_index = ring_index;
+		slot->flags = 0;
 
 		min_ring_index = Min(min_ring_index, ring_index);
 
@@ -2845,12 +2847,13 @@ neon_prefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 		}
 
 		tag.blockNum = blocknum;
-		
+
 		for (int i = 0; i < PG_IOV_MAX / 8; i++)
 			lfc_present[i] = ~(lfc_present[i]);
 
 		ring_index = prefetch_register_bufferv(tag, NULL, iterblocks,
 											   lfc_present, true);
+
 		nblocks -= iterblocks;
 		blocknum += iterblocks;