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authorKevin Wolf <kwolf@redhat.com>2015-09-14 15:33:33 +0200
committerKevin Wolf <kwolf@redhat.com>2015-10-16 15:34:29 +0200
commit5db15a57697063b9062a015dbc6d5d38211f2df1 (patch)
tree37f131976de33ffd0e9a17c885d5e88bab3f3096 /block.c
parent760e006384ecd5b8b8b1b91b5c85ff8fdcb3a21f (diff)
downloadqemu-arm-5db15a57697063b9062a015dbc6d5d38211f2df1.tar.gz
block: Manage backing file references in bdrv_set_backing_hd()
This simplifies the code somewhat, especially when dropping whole backing file subchains. The exception is the mirroring code that does adventurous things with bdrv_swap() and in order to keep it working, I had to duplicate most of bdrv_set_backing_hd() locally. We'll get rid again of this ugliness shortly. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c68
1 files changed, 18 insertions, 50 deletions
diff --git a/block.c b/block.c
index ecc0885fae..a9c7ea600c 100644
--- a/block.c
+++ b/block.c
@@ -1094,7 +1094,7 @@ static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
return child;
}
-static void bdrv_detach_child(BdrvChild *child)
+void bdrv_detach_child(BdrvChild *child)
{
QLIST_REMOVE(child, next);
g_free(child);
@@ -1112,13 +1112,20 @@ void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child)
bdrv_unref(child_bs);
}
+/*
+ * Sets the backing file link of a BDS. A new reference is created; callers
+ * which don't need their own reference any more must call bdrv_unref().
+ */
void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
{
+ if (backing_hd) {
+ bdrv_ref(backing_hd);
+ }
if (bs->backing) {
assert(bs->backing_blocker);
bdrv_op_unblock_all(bs->backing->bs, bs->backing_blocker);
- bdrv_detach_child(bs->backing);
+ bdrv_unref_child(bs, bs->backing);
} else if (backing_hd) {
error_setg(&bs->backing_blocker,
"node is used as backing hd of '%s'",
@@ -1214,7 +1221,10 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
goto free_exit;
}
+ /* Hook up the backing file link; drop our reference, bs owns the
+ * backing_hd reference now */
bdrv_set_backing_hd(bs, backing_hd);
+ bdrv_unref(backing_hd);
free_exit:
g_free(backing_filename);
@@ -1891,11 +1901,7 @@ void bdrv_close(BlockDriverState *bs)
bs->drv->bdrv_close(bs);
bs->drv = NULL;
- if (bs->backing) {
- BlockDriverState *backing_hd = bs->backing->bs;
- bdrv_set_backing_hd(bs, NULL);
- bdrv_unref(backing_hd);
- }
+ bdrv_set_backing_hd(bs, NULL);
if (bs->file != NULL) {
bdrv_unref_child(bs, bs->file);
@@ -2378,12 +2384,6 @@ BlockDriverState *bdrv_find_base(BlockDriverState *bs)
return bdrv_find_overlay(bs, NULL);
}
-typedef struct BlkIntermediateStates {
- BlockDriverState *bs;
- QSIMPLEQ_ENTRY(BlkIntermediateStates) entry;
-} BlkIntermediateStates;
-
-
/*
* Drops images above 'base' up to and including 'top', and sets the image
* above 'top' to have base as its backing file.
@@ -2416,15 +2416,9 @@ typedef struct BlkIntermediateStates {
int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
BlockDriverState *base, const char *backing_file_str)
{
- BlockDriverState *intermediate;
- BlockDriverState *base_bs = NULL;
BlockDriverState *new_top_bs = NULL;
- BlkIntermediateStates *intermediate_state, *next;
int ret = -EIO;
- QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete;
- QSIMPLEQ_INIT(&states_to_delete);
-
if (!top->drv || !base->drv) {
goto exit;
}
@@ -2443,48 +2437,22 @@ int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
goto exit;
}
- intermediate = top;
-
- /* now we will go down through the list, and add each BDS we find
- * into our deletion queue, until we hit the 'base'
- */
- while (intermediate) {
- intermediate_state = g_new0(BlkIntermediateStates, 1);
- intermediate_state->bs = intermediate;
- QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry);
-
- if (backing_bs(intermediate) == base) {
- base_bs = backing_bs(intermediate);
- break;
- }
- intermediate = backing_bs(intermediate);
- }
- if (base_bs == NULL) {
- /* something went wrong, we did not end at the base. safely
- * unravel everything, and exit with error */
+ /* Make sure that base is in the backing chain of top */
+ if (!bdrv_chain_contains(top, base)) {
goto exit;
}
/* success - we can delete the intermediate states, and link top->base */
- backing_file_str = backing_file_str ? backing_file_str : base_bs->filename;
+ backing_file_str = backing_file_str ? backing_file_str : base->filename;
ret = bdrv_change_backing_file(new_top_bs, backing_file_str,
- base_bs->drv ? base_bs->drv->format_name : "");
+ base->drv ? base->drv->format_name : "");
if (ret) {
goto exit;
}
- bdrv_set_backing_hd(new_top_bs, base_bs);
+ bdrv_set_backing_hd(new_top_bs, base);
- QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) {
- /* so that bdrv_close() does not recursively close the chain */
- bdrv_set_backing_hd(intermediate_state->bs, NULL);
- bdrv_unref(intermediate_state->bs);
- }
ret = 0;
-
exit:
- QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) {
- g_free(intermediate_state);
- }
return ret;
}