From 1e8113032f5b1efc5da66382470ce4809c76f8f2 Mon Sep 17 00:00:00 2001
From: Janosch Frank <frankja@linux.ibm.com>
Date: Thu, 11 Aug 2022 12:10:56 +0000
Subject: [PATCH] dump: Refactor dump_iterate and introduce
 dump_filter_memblock_*()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The iteration over the memblocks in dump_iterate() is hard to
understand so it's about time to clean it up. Instead of manually
grabbing the next memblock we can use QTAILQ_FOREACH to iterate over
all memblocks.

Additionally we move the calculation of the offset and length out by
introducing and using the dump_filter_memblock_*() functions. These
functions will later be used to cleanup other parts of dump.c.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220811121111.9878-4-frankja@linux.ibm.com>
---
 dump/dump.c | 80 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 45 insertions(+), 35 deletions(-)

diff --git a/dump/dump.c b/dump/dump.c
index 0ed7cf9c7b..340de5a1e7 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -591,31 +591,43 @@ static void dump_begin(DumpState *s, Error **errp)
     write_elf_notes(s, errp);
 }
 
-static int get_next_block(DumpState *s, GuestPhysBlock *block)
+static int64_t dump_filtered_memblock_size(GuestPhysBlock *block,
+                                           int64_t filter_area_start,
+                                           int64_t filter_area_length)
 {
-    while (1) {
-        block = QTAILQ_NEXT(block, next);
-        if (!block) {
-            /* no more block */
-            return 1;
-        }
+    int64_t size, left, right;
 
-        s->start = 0;
-        s->next_block = block;
-        if (s->has_filter) {
-            if (block->target_start >= s->begin + s->length ||
-                block->target_end <= s->begin) {
-                /* This block is out of the range */
-                continue;
-            }
-
-            if (s->begin > block->target_start) {
-                s->start = s->begin - block->target_start;
-            }
-        }
-
-        return 0;
+    /* No filter, return full size */
+    if (!filter_area_length) {
+        return block->target_end - block->target_start;
     }
+
+    /* calculate the overlapped region. */
+    left = MAX(filter_area_start, block->target_start);
+    right = MIN(filter_area_start + filter_area_length, block->target_end);
+    size = right - left;
+    size = size > 0 ? size : 0;
+
+    return size;
+}
+
+static int64_t dump_filtered_memblock_start(GuestPhysBlock *block,
+                                            int64_t filter_area_start,
+                                            int64_t filter_area_length)
+{
+    if (filter_area_length) {
+        /* return -1 if the block is not within filter area */
+        if (block->target_start >= filter_area_start + filter_area_length ||
+            block->target_end <= filter_area_start) {
+            return -1;
+        }
+
+        if (filter_area_start > block->target_start) {
+            return filter_area_start - block->target_start;
+        }
+    }
+
+    return 0;
 }
 
 /* write all memory to vmcore */
@@ -623,24 +635,22 @@ static void dump_iterate(DumpState *s, Error **errp)
 {
     ERRP_GUARD();
     GuestPhysBlock *block;
-    int64_t size;
+    int64_t memblock_size, memblock_start;
 
-    do {
-        block = s->next_block;
-
-        size = block->target_end - block->target_start;
-        if (s->has_filter) {
-            size -= s->start;
-            if (s->begin + s->length < block->target_end) {
-                size -= block->target_end - (s->begin + s->length);
-            }
+    QTAILQ_FOREACH(block, &s->guest_phys_blocks.head, next) {
+        memblock_start = dump_filtered_memblock_start(block, s->begin, s->length);
+        if (memblock_start == -1) {
+            continue;
         }
-        write_memory(s, block, s->start, size, errp);
+
+        memblock_size = dump_filtered_memblock_size(block, s->begin, s->length);
+
+        /* Write the memory to file */
+        write_memory(s, block, memblock_start, memblock_size, errp);
         if (*errp) {
             return;
         }
-
-    } while (!get_next_block(s, block));
+    }
 }
 
 static void create_vmcore(DumpState *s, Error **errp)