[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [RFC PATCH 09/41] block: Default .bdrv_child_perm() for for
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [RFC PATCH 09/41] block: Default .bdrv_child_perm() for format drivers |
Date: |
Mon, 13 Feb 2017 18:22:31 +0100 |
Almost all format drivers have the same characteristics as far as
permissions are concerned: They have one or more children for storing
their own data and, more importantly, metadata (can be written to and
grow even without external write requests, must be protected against
other writers and present consistent data) and optionally a backing file
(this is just data, so like for a filter, it only depends on what the
parent nodes need).
This provides a default implementation that can be shared by most of
our format drivers.
Signed-off-by: Kevin Wolf <address@hidden>
---
block.c | 37 +++++++++++++++++++++++++++++++++++++
include/block/block_int.h | 8 ++++++++
2 files changed, 45 insertions(+)
diff --git a/block.c b/block.c
index 290768d..8e99bb5 100644
--- a/block.c
+++ b/block.c
@@ -1459,6 +1459,43 @@ void bdrv_filter_default_perms(BlockDriverState *bs,
BdrvChild *c,
(c->shared_perm & DEFAULT_PERM_UNCHANGED);
}
+void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
+ const BdrvChildRole *role,
+ uint64_t perm, uint64_t shared,
+ uint64_t *nperm, uint64_t *nshared)
+{
+ bool backing = (role == &child_backing);
+ assert(role == &child_backing || role == &child_file);
+
+ if (!backing) {
+ /* Apart from the modifications below, the same permissions are
+ * forwarded and left alone as for filters */
+ bdrv_filter_default_perms(bs, c, role, perm, shared, &perm, &shared);
+
+ /* Format drivers may touch metadata even if the guest doesn't write */
+ if (!bdrv_is_read_only(bs)) {
+ perm |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
+ }
+
+ /* bs->file always needs to be consistent because of the metadata. We
+ * can never allow other users to resize or write to it. */
+ perm |= BLK_PERM_CONSISTENT_READ;
+ shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
+ } else {
+ /* We want consistent read from backing files if the parent needs it.
+ * No other operations are performed on backing files. */
+ perm &= BLK_PERM_CONSISTENT_READ;
+
+ /* If the parent can deal with changing data, we're okay with a
+ * writable backing file. */
+ shared &= BLK_PERM_WRITE;
+ shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD |
+ BLK_PERM_WRITE_UNCHANGED;
+ }
+
+ *nperm = perm;
+ *nshared = shared;
+}
static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
{
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 2d74f92..46f51a6 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -885,6 +885,14 @@ void bdrv_filter_default_perms(BlockDriverState *bs,
BdrvChild *c,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared);
+/* Default implementation for BlockDriver.bdrv_child_perm() that can be used by
+ * (non-raw) image formats: Like above for bs->backing, but for bs->file it
+ * requires WRITE | RESIZE for read-write images, always requires
+ * CONSISTENT_READ and doesn't share WRITE. */
+void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
+ const BdrvChildRole *role,
+ uint64_t perm, uint64_t shared,
+ uint64_t *nperm, uint64_t *nshared);
const char *bdrv_get_parent_name(const BlockDriverState *bs);
void blk_dev_change_media_cb(BlockBackend *blk, bool load);
--
1.8.3.1
- [Qemu-devel] [RFC PATCH 00/41] New op blocker system, Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 02/41] block: Add op blocker permission constants, Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 03/41] block: Add Error argument to bdrv_attach_child(), Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 01/41] block: Attach bs->file only during .bdrv_open(), Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 04/41] block: Let callers request permissions when attaching a child node, Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 05/41] tests: Use opened block node for block job tests, Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 07/41] block: Default .bdrv_child_perm() for filter drivers, Kevin Wolf, 2017/02/13
- [Qemu-devel] [RFC PATCH 09/41] block: Default .bdrv_child_perm() for format drivers,
Kevin Wolf <=
- Re: [Qemu-devel] [RFC PATCH 09/41] block: Default .bdrv_child_perm() for format drivers, Max Reitz, 2017/02/15
[Qemu-devel] [RFC PATCH 06/41] block: Involve block drivers in permission granting, Kevin Wolf, 2017/02/13