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block: Manage backing file references in bdrv_set_backing_hd()

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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>
This commit is contained in:
Kevin Wolf 2015-09-14 15:33:33 +02:00
parent 760e006384
commit 5db15a5769
5 changed files with 37 additions and 84 deletions
Download patch file Download diff file Expand all files Collapse all files

68
block.c
View file

@ -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;
}