Message ID | 1333640581-25649-5-git-send-email-pbonzini@redhat.com |
---|---|
State | New |
Headers | show |
----- Original Message ----- > From: "Paolo Bonzini" <pbonzini@redhat.com> > To: qemu-devel@nongnu.org > Cc: "Marcelo Tosatti" <mtosatti@redhat.com>, "Federico Simoncelli" <fsimonce@redhat.com> > Sent: Thursday, April 5, 2012 5:42:58 PM > Subject: [PATCH 4/7] block: close unused image files at the end of streaming > > From: Marcelo Tosatti <mtosatti@redhat.com> > > 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. s/relative/absolute/ > 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. The patch is fine but I disagree with this comment. The user/admin didn't make any mistake and he shouldn't be in charge of additional maintenance (which is also tricky since the VM is running).
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);