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commit: Deal with filters 

This includes some permission limiting (for example, we only need to
take the RESIZE permission if the base is smaller than the top).

Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-06-12 17:47:37 +02:00 committed by Kevin Wolf
parent 2b088c60bb
commit 9a71b9de3f
4 changed files with 79 additions and 28 deletions
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7
block/block-backend.c
View File

@ -2279,10 +2279,13 @@ int blk_commit_all(void)
while ((blk = blk_all_next(blk)) != NULL) {
AioContext *aio_context = blk_get_aio_context(blk);
BlockDriverState *unfiltered_bs = bdrv_skip_filters(blk_bs(blk));
aio_context_acquire(aio_context);
if (blk_is_inserted(blk) && blk->root->bs->backing) {
int ret = bdrv_commit(blk->root->bs);
if (blk_is_inserted(blk) && bdrv_cow_child(unfiltered_bs)) {
int ret;
ret = bdrv_commit(unfiltered_bs);
if (ret < 0) {
aio_context_release(aio_context);
return ret;

94
block/commit.c
View File

@ -37,6 +37,7 @@ typedef struct CommitBlockJob {
BlockBackend *top;
BlockBackend *base;
BlockDriverState *base_bs;
BlockDriverState *base_overlay;
BlockdevOnError on_error;
bool base_read_only;
bool chain_frozen;
@ -89,7 +90,7 @@ static void commit_abort(Job *job)
* XXX Can (or should) we somehow keep 'consistent read' blocked even
* after the failed/cancelled commit job is gone? If we already wrote
* something to base, the intermediate images aren't valid any more. */
bdrv_replace_node(s->commit_top_bs, backing_bs(s->commit_top_bs),
bdrv_replace_node(s->commit_top_bs, s->commit_top_bs->backing->bs,
&error_abort);
bdrv_unref(s->commit_top_bs);
@ -153,7 +154,7 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
break;
}
/* Copy if allocated above the base */
ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base), false,
ret = bdrv_is_allocated_above(blk_bs(s->top), s->base_overlay, true,
offset, COMMIT_BUFFER_SIZE, &n);
copy = (ret == 1);
trace_commit_one_iteration(s, offset, n, ret);
@ -253,15 +254,35 @@ void commit_start(const char *job_id, BlockDriverState *bs,
CommitBlockJob *s;
BlockDriverState *iter;
BlockDriverState *commit_top_bs = NULL;
BlockDriverState *filtered_base;
Error *local_err = NULL;
int64_t base_size, top_size;
uint64_t base_perms, iter_shared_perms;
int ret;
assert(top != bs);
if (top == base) {
if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) {
error_setg(errp, "Invalid files for merge: top and base are the same");
return;
}
base_size = bdrv_getlength(base);
if (base_size < 0) {
error_setg_errno(errp, -base_size, "Could not inquire base image size");
return;
}
top_size = bdrv_getlength(top);
if (top_size < 0) {
error_setg_errno(errp, -top_size, "Could not inquire top image size");
return;
}
base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
if (base_size < top_size) {
base_perms |= BLK_PERM_RESIZE;
}
s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
speed, creation_flags, NULL, NULL, errp);
if (!s) {
@ -301,17 +322,43 @@ void commit_start(const char *job_id, BlockDriverState *bs,
s->commit_top_bs = commit_top_bs;
/* Block all nodes between top and base, because they will
* disappear from the chain after this operation. */
assert(bdrv_chain_contains(top, base));
for (iter = top; iter != base; iter = backing_bs(iter)) {
/* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
* at s->base (if writes are blocked for a node, they are also blocked
* for its backing file). The other options would be a second filter
* driver above s->base. */
/*
* Block all nodes between top and base, because they will
* disappear from the chain after this operation.
* Note that this assumes that the user is fine with removing all
* nodes (including R/W filters) between top and base. Assuring
* this is the responsibility of the interface (i.e. whoever calls
* commit_start()).
*/
s->base_overlay = bdrv_find_overlay(top, base);
assert(s->base_overlay);
/*
* The topmost node with
* bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)
*/
filtered_base = bdrv_cow_bs(s->base_overlay);
assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base));
/*
* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
* at s->base (if writes are blocked for a node, they are also blocked
* for its backing file). The other options would be a second filter
* driver above s->base.
*/
iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) {
if (iter == filtered_base) {
/*
* From here on, all nodes are filters on the base. This
* allows us to share BLK_PERM_CONSISTENT_READ.
*/
iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
}
ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE,
errp);
iter_shared_perms, errp);
if (ret < 0) {
goto fail;
}
@ -328,9 +375,7 @@ void commit_start(const char *job_id, BlockDriverState *bs,
}
s->base = blk_new(s->common.job.aio_context,
BLK_PERM_CONSISTENT_READ
| BLK_PERM_WRITE
| BLK_PERM_RESIZE,
base_perms,
BLK_PERM_CONSISTENT_READ
| BLK_PERM_GRAPH_MOD
| BLK_PERM_WRITE_UNCHANGED);
@ -398,19 +443,22 @@ int bdrv_commit(BlockDriverState *bs)
if (!drv)
return -ENOMEDIUM;
if (!bs->backing) {
backing_file_bs = bdrv_cow_bs(bs);
if (!backing_file_bs) {
return -ENOTSUP;
}
if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL))
{
return -EBUSY;
}
ro = bs->backing->bs->read_only;
ro = backing_file_bs->read_only;
if (ro) {
if (bdrv_reopen_set_read_only(bs->backing->bs, false, NULL)) {
if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) {
return -EACCES;
}
}
@ -428,8 +476,6 @@ int bdrv_commit(BlockDriverState *bs)
}
/* Insert commit_top block node above backing, so we can write to it */
backing_file_bs = backing_bs(bs);
commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
&local_err);
if (commit_top_bs == NULL) {
@ -515,7 +561,7 @@ ro_cleanup:
qemu_vfree(buf);
blk_unref(backing);
if (backing_file_bs) {
if (bdrv_cow_bs(bs) != backing_file_bs) {
bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
}
bdrv_unref(commit_top_bs);
@ -523,7 +569,7 @@ ro_cleanup:
if (ro) {
/* ignoring error return here */
bdrv_reopen_set_read_only(bs->backing->bs, true, NULL);
bdrv_reopen_set_read_only(backing_file_bs, true, NULL);
}
return ret;

2
block/monitor/block-hmp-cmds.c
View File

@ -217,7 +217,7 @@ void hmp_commit(Monitor *mon, const QDict *qdict)
return;
}
bs = blk_bs(blk);
bs = bdrv_skip_implicit_filters(blk_bs(blk));
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);

4
blockdev.c
View File

@ -2703,7 +2703,9 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
assert(bdrv_get_aio_context(base_bs) == aio_context);
for (iter = top_bs; iter != backing_bs(base_bs); iter = backing_bs(iter)) {
for (iter = top_bs; iter != bdrv_filter_or_cow_bs(base_bs);
iter = bdrv_filter_or_cow_bs(iter))
{
if (bdrv_op_is_blocked(iter, BLOCK_OP_TYPE_COMMIT_TARGET, errp)) {
goto out;
}