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block: Protect bs->backing with graph_lock

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Almost all functions that access bs->backing already take the graph
lock now. Add locking to the remaining users and finally annotate the
struct field itself as protected by the graph lock.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-18-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf
2023-10-27 17:53:26 +02:00
parent ccd6a37947
commit 004915a96a
9 changed files with 70 additions and 27 deletions
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27
block.c
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@ -3560,10 +3560,14 @@ out:
int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
Error **errp)
{
BlockDriverState *drain_bs = bs->backing ? bs->backing->bs : bs;
BlockDriverState *drain_bs;
int ret;
GLOBAL_STATE_CODE();
bdrv_graph_rdlock_main_loop();
drain_bs = bs->backing ? bs->backing->bs : bs;
bdrv_graph_rdunlock_main_loop();
bdrv_ref(drain_bs);
bdrv_drained_begin(drain_bs);
bdrv_graph_wrlock(backing_hd);
@ -3602,6 +3606,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
Error *local_err = NULL;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
if (bs->backing != NULL) {
goto free_exit;
@ -3643,10 +3648,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
implicit_backing = !strcmp(bs->auto_backing_file, bs->backing_file);
}
bdrv_graph_rdlock_main_loop();
backing_filename = bdrv_get_full_backing_filename(bs, &local_err);
bdrv_graph_rdunlock_main_loop();
if (local_err) {
ret = -EINVAL;
error_propagate(errp, local_err);
@ -3677,9 +3679,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
}
if (implicit_backing) {
bdrv_graph_rdlock_main_loop();
bdrv_refresh_filename(backing_hd);
bdrv_graph_rdunlock_main_loop();
pstrcpy(bs->auto_backing_file, sizeof(bs->auto_backing_file),
backing_hd->filename);
}
@ -4750,8 +4750,8 @@ bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
{
BlockDriverState *bs = reopen_state->bs;
BlockDriverState *new_child_bs;
BlockDriverState *old_child_bs = is_backing ? child_bs(bs->backing) :
child_bs(bs->file);
BlockDriverState *old_child_bs;
const char *child_name = is_backing ? "backing" : "file";
QObject *value;
const char *str;
@ -4797,6 +4797,7 @@ bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
g_assert_not_reached();
}
old_child_bs = is_backing ? child_bs(bs->backing) : child_bs(bs->file);
if (old_child_bs == new_child_bs) {
ret = 0;
goto out_rdlock;
@ -5008,13 +5009,16 @@ bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
* file or if the image file has a backing file name as part of
* its metadata. Otherwise the 'backing' option can be omitted.
*/
bdrv_graph_rdlock_main_loop();
if (drv->supports_backing && reopen_state->backing_missing &&
(reopen_state->bs->backing || reopen_state->bs->backing_file[0])) {
error_setg(errp, "backing is missing for '%s'",
reopen_state->bs->node_name);
bdrv_graph_rdunlock_main_loop();
ret = -EINVAL;
goto error;
}
bdrv_graph_rdunlock_main_loop();
/*
* Allow changing the 'backing' option. The new value can be
@ -5204,10 +5208,11 @@ static void bdrv_close(BlockDriverState *bs)
QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
bdrv_unref_child(bs, child);
}
bdrv_graph_wrunlock();
assert(!bs->backing);
assert(!bs->file);
bdrv_graph_wrunlock();
g_free(bs->opaque);
bs->opaque = NULL;
qatomic_set(&bs->copy_on_read, 0);
@ -5531,7 +5536,9 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
GLOBAL_STATE_CODE();
bdrv_graph_rdlock_main_loop();
assert(!bs_new->backing);
bdrv_graph_rdunlock_main_loop();
old_context = bdrv_get_aio_context(bs_top);
bdrv_drained_begin(bs_top);
@ -8115,7 +8122,7 @@ static bool append_strong_runtime_options(QDict *d, BlockDriverState *bs)
/* Note: This function may return false positives; it may return true
* even if opening the backing file specified by bs's image header
* would result in exactly bs->backing. */
static bool bdrv_backing_overridden(BlockDriverState *bs)
static bool GRAPH_RDLOCK bdrv_backing_overridden(BlockDriverState *bs)
{
GLOBAL_STATE_CODE();
if (bs->backing) {