Fix some BufFileRead() error reporting

Remove "%m" from error messages where errno would be bogus.  Add short
read byte counts where appropriate.

This is equivalent to what was done in
7897e3b, but some code was apparently
developed concurrently to that and not updated accordingly.

Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/f3501945-c591-8cc3-5ef0-b72a2e0eaa9c@enterprisedb.com

Author: petere

src/backend/backup/backup_manifest.c

@@ -371,7 +371,8 @@ SendBackupManifest(backup_manifest_info *manifest, bbsink *sink)
 		if (rc != bytes_to_read)
 			ereport(ERROR,
 					(errcode_for_file_access(),
-					 errmsg("could not read from temporary file: %m")));
+					 errmsg("could not read from temporary file: read only %zu of %zu bytes",
+							rc, bytes_to_read)));
 		bbsink_manifest_contents(sink, bytes_to_read);
 		manifest_bytes_done += bytes_to_read;
 	}

src/backend/replication/logical/worker.c

@@ -1398,7 +1398,7 @@ apply_spooled_messages(TransactionId xid, XLogRecPtr lsn)
 	nchanges = 0;
 	while (true)
 	{
-		int			nbytes;
+		size_t		nbytes;
 		int			len;
 
 		CHECK_FOR_INTERRUPTS();
@@ -1414,8 +1414,8 @@ apply_spooled_messages(TransactionId xid, XLogRecPtr lsn)
 		if (nbytes != sizeof(len))
 			ereport(ERROR,
 					(errcode_for_file_access(),
-					 errmsg("could not read from streaming transaction's changes file \"%s\": %m",
-							path)));
+					 errmsg("could not read from streaming transaction's changes file \"%s\": read only %zu of %zu bytes",
+							path, nbytes, sizeof(len))));
 
 		if (len <= 0)
 			elog(ERROR, "incorrect length %d in streaming transaction's changes file \"%s\"",
@@ -1425,11 +1425,12 @@ apply_spooled_messages(TransactionId xid, XLogRecPtr lsn)
 		buffer = repalloc(buffer, len);
 
 		/* and finally read the data into the buffer */
-		if (BufFileRead(fd, buffer, len) != len)
+		nbytes = BufFileRead(fd, buffer, len);
+		if (nbytes != len)
 			ereport(ERROR,
 					(errcode_for_file_access(),
-					 errmsg("could not read from streaming transaction's changes file \"%s\": %m",
-							path)));
+					 errmsg("could not read from streaming transaction's changes file \"%s\": read only %zu of %zu bytes",
+							path, nbytes, (size_t) len)));
 
 		/* copy the buffer to the stringinfo and call apply_dispatch */
 		resetStringInfo(&s2);
@@ -3192,6 +3193,7 @@ static void
 subxact_info_read(Oid subid, TransactionId xid)
 {
 	char		path[MAXPGPATH];
+	size_t		nread;
 	Size		len;
 	BufFile    *fd;
 	MemoryContext oldctx;
@@ -3211,13 +3213,12 @@ subxact_info_read(Oid subid, TransactionId xid)
 		return;
 
 	/* read number of subxact items */
-	if (BufFileRead(fd, &subxact_data.nsubxacts,
-					sizeof(subxact_data.nsubxacts)) !=
-		sizeof(subxact_data.nsubxacts))
+	nread = BufFileRead(fd, &subxact_data.nsubxacts, sizeof(subxact_data.nsubxacts));
+	if (nread != sizeof(subxact_data.nsubxacts))
 		ereport(ERROR,
 				(errcode_for_file_access(),
-				 errmsg("could not read from streaming transaction's subxact file \"%s\": %m",
-						path)));
+				 errmsg("could not read from streaming transaction's subxact file \"%s\": read only %zu of %zu bytes",
+						path, nread, sizeof(subxact_data.nsubxacts))));
 
 	len = sizeof(SubXactInfo) * subxact_data.nsubxacts;
 
@@ -3235,11 +3236,15 @@ subxact_info_read(Oid subid, TransactionId xid)
 								   sizeof(SubXactInfo));
 	MemoryContextSwitchTo(oldctx);
 
-	if ((len > 0) && ((BufFileRead(fd, subxact_data.subxacts, len)) != len))
+	if (len > 0)
+	{
+		nread = BufFileRead(fd, subxact_data.subxacts, len);
+		if (nread != len)
 		ereport(ERROR,
 				(errcode_for_file_access(),
-				 errmsg("could not read from streaming transaction's subxact file \"%s\": %m",
-						path)));
+				 errmsg("could not read from streaming transaction's subxact file \"%s\": read only %zu of %zu bytes",
+						path, nread, len)));
+	}
 
 	BufFileClose(fd);
 }