nbdkit/0016-cow-Add-some-more-debugging-especially-for-blk_read_.patch

From a22248e3075e782d28542f8f6acd046c9dfa8998 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Mon, 9 Aug 2021 14:09:31 +0100
Subject: [PATCH] cow: Add some more debugging especially for blk_read_multiple
 and cow-on-read

Only activated when we use -D cow.verbose=1

(cherry picked from commit 2da1ae0ca966af955d8fcf3feffffc80d07142fd)
---
 filters/cow/blk.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/filters/cow/blk.c b/filters/cow/blk.c
index 4f84e092..c22d5886 100644
--- a/filters/cow/blk.c
+++ b/filters/cow/blk.c
@@ -254,8 +254,10 @@ blk_read_multiple (nbdkit_next *next,
 
   if (cow_debug_verbose)
     nbdkit_debug ("cow: blk_read_multiple block %" PRIu64
-                  " (offset %" PRIu64 ") is %s",
-                  blknum, (uint64_t) offset, state_to_string (state));
+                  " (offset %" PRIu64 ") run of length %" PRIu64
+                  " is %s",
+                  blknum, (uint64_t) offset, runblocks,
+                  state_to_string (state));
 
   if (state == BLOCK_NOT_ALLOCATED) { /* Read underlying plugin. */
     unsigned n, tail = 0;
@@ -281,6 +283,11 @@ blk_read_multiple (nbdkit_next *next,
      * set them as allocated.
      */
     if (cow_on_read) {
+      if (cow_debug_verbose)
+        nbdkit_debug ("cow: cow-on-read saving %" PRIu64 " blocks "
+                      "at offset %" PRIu64 " into the cache",
+                      runblocks, offset);
+
       if (full_pwrite (fd, block, BLKSIZE * runblocks, offset) == -1) {
         *err = errno;
         nbdkit_error ("pwrite: %m");
-- 
2.31.1