lib-index: mail_transaction_log_sync_lock() - Fix function's comment

diff --git a/src/lib-index/mail-transaction-log.h b/src/lib-index/mail-transaction-log.h
index dab52c6bcc855f62d463261772446f19e43bbab8..c977361a5f8f3d84e624b65b575c02d1b91c4626 100644 (file)
--- a/src/lib-index/mail-transaction-log.h
+++ b/src/lib-index/mail-transaction-log.h
@@ -287,8 +287,14 @@ void mail_transaction_log_append_add(struct mail_transaction_log_append_ctx *ctx
                                     const void *data, size_t size);
 int mail_transaction_log_append_commit(struct mail_transaction_log_append_ctx **ctx);
 
-/* Lock transaction log for index synchronization. Log cannot be read or
-   written to while it's locked. Returns end offset. */
+/* Lock transaction log for index synchronization. This is used as the main
+   exclusive lock for index changes. The index/log can still be read since they
+   don't use locking, but the log can't be written to while it's locked.
+   Returns 0 on success, -1 if locking failed for any reason.
+
+   After successfully locking the transaction log, the log file is also fully
+   mapped into memory and its sync_offset updated. The locked file's sequence
+   and sync_offset are returned. */
 int mail_transaction_log_sync_lock(struct mail_transaction_log *log,
                                   const char *lock_reason,
                                   uint32_t *file_seq_r, uoff_t *file_offset_r);