From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Fri, 8 Apr 2022 12:59:59 +0000 (+0300)
Subject: lib-index: Always write tail offset the same as head offset
X-Git-Tag: 2.3.19~12
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0dd36a73e492159221293bd63fbe46bded43d0d1;p=thirdparty%2Fdovecot%2Fcore.git

lib-index: Always write tail offset the same as head offset

The mail_index_write() must not be called unless this is safe to do.
This prevents unnecessarily reading through dovecot.index.log between
tail..head offsets, which can be expensive due to modseq calculation.
---

diff --git a/src/lib-index/mail-index-write.c b/src/lib-index/mail-index-write.c
index 9fb5784480..689cb9cdc1 100644
--- a/src/lib-index/mail-index-write.c
+++ b/src/lib-index/mail-index-write.c
@@ -78,12 +78,18 @@ static int mail_index_recreate(struct mail_index *index)
 	output = o_stream_create_fd_file(fd, 0, FALSE);
 	o_stream_cork(output);
 
-	base_size = I_MIN(map->hdr.base_header_size, sizeof(map->hdr));
-	o_stream_nsend(output, &map->hdr, base_size);
+	struct mail_index_header hdr = map->hdr;
+	/* Write tail_offset the same as head_offset. This function must not
+	   be called unless it's safe to do this. See the explanations in
+	   mail_index_sync_commit(). */
+	hdr.log_file_tail_offset = hdr.log_file_head_offset;
+
+	base_size = I_MIN(hdr.base_header_size, sizeof(hdr));
+	o_stream_nsend(output, &hdr, base_size);
 	o_stream_nsend(output, MAIL_INDEX_MAP_HDR_OFFSET(map, base_size),
-		       map->hdr.header_size - base_size);
+		       hdr.header_size - base_size);
 	o_stream_nsend(output, map->rec_map->records,
-		       map->rec_map->records_count * map->hdr.record_size);
+		       map->rec_map->records_count * hdr.record_size);
 	if (o_stream_finish(output) < 0) {
 		mail_index_file_set_syscall_error(index, path, "write()");
 		ret = -1;