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block: Use CAFs when working with backing chains

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Use child access functions when iterating through backing chains so
filters do not break the chain.

In addition, bdrv_find_overlay() will now always return the actual
overlay; that is, it will never return a filter node but only one with a
COW backing file (there may be filter nodes between that node and @bs).

Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-06-12 17:34:45 +02:00 committed by Kevin Wolf
parent 67acfd2188
commit dcf3f9b268
1 changed files with 30 additions and 14 deletions
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44
block.c
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@ -4745,9 +4745,9 @@ int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
}
/*
* Finds the image layer in the chain that has 'bs' as its backing file.
*
* active is the current topmost image.
* Finds the first non-filter node above bs in the chain between
* active and bs. The returned node is either an immediate parent of
* bs, or there are only filter nodes between the two.
*
* Returns NULL if bs is not found in active's image chain,
* or if active == bs.
@ -4757,11 +4757,18 @@ int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
BlockDriverState *bs)
{
while (active && bs != backing_bs(active)) {
active = backing_bs(active);
bs = bdrv_skip_filters(bs);
active = bdrv_skip_filters(active);
while (active) {
BlockDriverState *next = bdrv_backing_chain_next(active);
if (bs == next) {
return active;
}
active = next;
}
return active;
return NULL;
}
/* Given a BDS, searches for the base layer. */
@ -4913,9 +4920,7 @@ int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base,
* other intermediate nodes have been dropped.
* If 'top' is an implicit node (e.g. "commit_top") we should skip
* it because no one inherits from it. We use explicit_top for that. */
while (explicit_top && explicit_top->implicit) {
explicit_top = backing_bs(explicit_top);
}
explicit_top = bdrv_skip_implicit_filters(explicit_top);
update_inherits_from = bdrv_inherits_from_recursive(base, explicit_top);
/* success - we can delete the intermediate states, and link top->base */
@ -5372,7 +5377,7 @@ BlockDriverState *bdrv_lookup_bs(const char *device,
bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
{
while (top && top != base) {
top = backing_bs(top);
top = bdrv_filter_or_cow_bs(top);
}
return top != NULL;
@ -5613,6 +5618,7 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
int is_protocol = 0;
BlockDriverState *curr_bs = NULL;
BlockDriverState *retval = NULL;
BlockDriverState *bs_below;
if (!bs || !bs->drv || !backing_file) {
return NULL;
@ -5623,7 +5629,17 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
is_protocol = path_has_protocol(backing_file);
for (curr_bs = bs; curr_bs->backing; curr_bs = curr_bs->backing->bs) {
/*
* Being largely a legacy function, skip any filters here
* (because filters do not have normal filenames, so they cannot
* match anyway; and allowing json:{} filenames is a bit out of
* scope).
*/
for (curr_bs = bdrv_skip_filters(bs);
bdrv_cow_child(curr_bs) != NULL;
curr_bs = bs_below)
{
bs_below = bdrv_backing_chain_next(curr_bs);
/* If either of the filename paths is actually a protocol, then
* compare unmodified paths; otherwise make paths relative */
@ -5631,7 +5647,7 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
char *backing_file_full_ret;
if (strcmp(backing_file, curr_bs->backing_file) == 0) {
retval = curr_bs->backing->bs;
retval = bs_below;
break;
}
/* Also check against the full backing filename for the image */
@ -5641,7 +5657,7 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
bool equal = strcmp(backing_file, backing_file_full_ret) == 0;
g_free(backing_file_full_ret);
if (equal) {
retval = curr_bs->backing->bs;
retval = bs_below;
break;
}
}
@ -5667,7 +5683,7 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
g_free(filename_tmp);
if (strcmp(backing_file_full, filename_full) == 0) {
retval = curr_bs->backing->bs;
retval = bs_below;
break;
}
}