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[PULL 31/64] block: Re-evaluate backing file handling in reopen
From: |
Kevin Wolf |
Subject: |
[PULL 31/64] block: Re-evaluate backing file handling in reopen |
Date: |
Mon, 7 Sep 2020 13:09:03 +0200 |
From: Max Reitz <mreitz@redhat.com>
Reopening a node's backing child needs a bit of special handling because
the "backing" child has different defaults than all other children
(among other things). Adding filter support here is a bit more
difficult than just using the child access functions. In fact, we often
have to directly use bs->backing because these functions are about the
"backing" child (which may or may not be the COW backing file).
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
block.c | 49 ++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 40 insertions(+), 9 deletions(-)
diff --git a/block.c b/block.c
index 96bf8672f1..660386795a 100644
--- a/block.c
+++ b/block.c
@@ -4004,7 +4004,7 @@ static int bdrv_reopen_parse_backing(BDRVReopenState
*reopen_state,
Error **errp)
{
BlockDriverState *bs = reopen_state->bs;
- BlockDriverState *overlay_bs, *new_backing_bs;
+ BlockDriverState *overlay_bs, *below_bs, *new_backing_bs;
QObject *value;
const char *str;
@@ -4043,26 +4043,57 @@ static int bdrv_reopen_parse_backing(BDRVReopenState
*reopen_state,
}
}
+ /*
+ * Ensure that @bs can really handle backing files, because we are
+ * about to give it one (or swap the existing one)
+ */
+ if (bs->drv->is_filter) {
+ /* Filters always have a file or a backing child */
+ if (!bs->backing) {
+ error_setg(errp, "'%s' is a %s filter node that does not support a
"
+ "backing child", bs->node_name, bs->drv->format_name);
+ return -EINVAL;
+ }
+ } else if (!bs->drv->supports_backing) {
+ error_setg(errp, "Driver '%s' of node '%s' does not support backing "
+ "files", bs->drv->format_name, bs->node_name);
+ return -EINVAL;
+ }
+
/*
* Find the "actual" backing file by skipping all links that point
* to an implicit node, if any (e.g. a commit filter node).
+ * We cannot use any of the bdrv_skip_*() functions here because
+ * those return the first explicit node, while we are looking for
+ * its overlay here.
*/
overlay_bs = bs;
- while (backing_bs(overlay_bs) && backing_bs(overlay_bs)->implicit) {
- overlay_bs = backing_bs(overlay_bs);
+ for (below_bs = bdrv_filter_or_cow_bs(overlay_bs);
+ below_bs && below_bs->implicit;
+ below_bs = bdrv_filter_or_cow_bs(overlay_bs))
+ {
+ overlay_bs = below_bs;
}
/* If we want to replace the backing file we need some extra checks */
- if (new_backing_bs != backing_bs(overlay_bs)) {
+ if (new_backing_bs != bdrv_filter_or_cow_bs(overlay_bs)) {
/* Check for implicit nodes between bs and its backing file */
if (bs != overlay_bs) {
error_setg(errp, "Cannot change backing link if '%s' has "
"an implicit backing file", bs->node_name);
return -EPERM;
}
- /* Check if the backing link that we want to replace is frozen */
- if (bdrv_is_backing_chain_frozen(overlay_bs, backing_bs(overlay_bs),
- errp)) {
+ /*
+ * Check if the backing link that we want to replace is frozen.
+ * Note that
+ * bdrv_filter_or_cow_child(overlay_bs) == overlay_bs->backing,
+ * because we know that overlay_bs == bs, and that @bs
+ * either is a filter that uses ->backing or a COW format BDS
+ * with bs->drv->supports_backing == true.
+ */
+ if (bdrv_is_backing_chain_frozen(overlay_bs,
+ child_bs(overlay_bs->backing), errp))
+ {
return -EPERM;
}
reopen_state->replace_backing_bs = true;
@@ -4211,7 +4242,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
BlockReopenQueue *queue,
* its metadata. Otherwise the 'backing' option can be omitted.
*/
if (drv->supports_backing && reopen_state->backing_missing &&
- (backing_bs(reopen_state->bs) || reopen_state->bs->backing_file[0])) {
+ (reopen_state->bs->backing || reopen_state->bs->backing_file[0])) {
error_setg(errp, "backing is missing for '%s'",
reopen_state->bs->node_name);
ret = -EINVAL;
@@ -4352,7 +4383,7 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
* from bdrv_set_backing_hd()) has the new values.
*/
if (reopen_state->replace_backing_bs) {
- BlockDriverState *old_backing_bs = backing_bs(bs);
+ BlockDriverState *old_backing_bs = child_bs(bs->backing);
assert(!old_backing_bs || !old_backing_bs->implicit);
/* Abort the permission update on the backing bs we're detaching */
if (old_backing_bs) {
--
2.25.4
- [PULL 20/64] block: bdrv_set_backing_hd() is about bs->backing, (continued)
- [PULL 20/64] block: bdrv_set_backing_hd() is about bs->backing, Kevin Wolf, 2020/09/07
- [PULL 21/64] block: Include filters when freezing backing chain, Kevin Wolf, 2020/09/07
- [PULL 23/64] block: Add bdrv_supports_compressed_writes(), Kevin Wolf, 2020/09/07
- [PULL 24/64] throttle: Support compressed writes, Kevin Wolf, 2020/09/07
- [PULL 26/64] block: Use bdrv_filter_(bs|child) where obvious, Kevin Wolf, 2020/09/07
- [PULL 22/64] block: Drop bdrv_is_encrypted(), Kevin Wolf, 2020/09/07
- [PULL 27/64] block: Use CAFs in block status functions, Kevin Wolf, 2020/09/07
- [PULL 25/64] copy-on-read: Support compressed writes, Kevin Wolf, 2020/09/07
- [PULL 28/64] stream: Deal with filters, Kevin Wolf, 2020/09/07
- [PULL 30/64] block: Use bdrv_cow_child() in bdrv_co_truncate(), Kevin Wolf, 2020/09/07
- [PULL 31/64] block: Re-evaluate backing file handling in reopen,
Kevin Wolf <=
- [PULL 29/64] block: Use CAFs when working with backing chains, Kevin Wolf, 2020/09/07
- [PULL 38/64] block: Use CAFs for debug breakpoints, Kevin Wolf, 2020/09/07
- [PULL 32/64] block: Flush all children in generic code, Kevin Wolf, 2020/09/07
- [PULL 39/64] block: Improve get_allocated_file_size's default, Kevin Wolf, 2020/09/07
- [PULL 40/64] block/null: Implement bdrv_get_allocated_file_size, Kevin Wolf, 2020/09/07
- [PULL 34/64] block: Iterate over children in refresh_limits, Kevin Wolf, 2020/09/07
- [PULL 35/64] block: Use CAFs in bdrv_refresh_filename(), Kevin Wolf, 2020/09/07
- [PULL 41/64] blockdev: Use CAF in external_snapshot_prepare(), Kevin Wolf, 2020/09/07
- [PULL 36/64] block: Use CAF in bdrv_co_rw_vmstate(), Kevin Wolf, 2020/09/07
- [PULL 43/64] block: Use child access functions for QAPI queries, Kevin Wolf, 2020/09/07