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[Qemu-devel] [PATCH 4/7] block: close unused image files at the end of s


From: Paolo Bonzini
Subject: [Qemu-devel] [PATCH 4/7] block: close unused image files at the end of streaming
Date: Thu, 5 Apr 2012 17:42:58 +0200

From: Marcelo Tosatti <address@hidden>

Close the now unused images that were part of the previous backing file
chain and adjust ->backing_hd properly.

Note that this only works with relative paths.
Given the images:

 /tmp/a/base.raw
 /tmp/a/snap1.qcow2
 /tmp/b/snap2.qcow2

chained as:

 base(bak:"") <- snap1(bak:"base.raw") <- snap2(bak:"../a/snap1.qcow2")

merging snap1 and snap2 we will obtain:

 base(bak:"") <- snap2(bak:"base.raw")

However this should be maintained by the user/admin: one can also
screw up relative paths using qemu-img manually.

Signed-off-by: Marcelo Tosatti <address@hidden>
Cc: Federico Simoncelli <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
 block/stream.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/block/stream.c b/block/stream.c
index 61ff7a2..54f2b39 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -76,6 +76,28 @@ static int coroutine_fn stream_populate(BlockDriverState *bs,
     return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
 }
 
+static void close_unused_images(BlockDriverState *top, BlockDriverState *base,
+                                const char *base_id)
+{
+    BlockDriverState *intermediate;
+    intermediate = top->backing_hd;
+
+    while (intermediate) {
+        BlockDriverState *unused;
+
+        /* reached base */
+        if (intermediate == base) {
+            break;
+        }
+
+        unused = intermediate;
+        intermediate = intermediate->backing_hd;
+        unused->backing_hd = NULL;
+        bdrv_delete(unused);
+    }
+    top->backing_hd = base;
+}
+
 /*
  * Given an image chain: [BASE] -> [INTER1] -> [INTER2] -> [TOP]
  *
@@ -223,6 +245,7 @@ retry:
             base_id = s->backing_file_id;
         }
         ret = bdrv_change_backing_file(bs, base_id, NULL);
+        close_unused_images(bs, base, base_id);
     }
 
     qemu_vfree(buf);
-- 
1.7.9.3





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