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[Qemu-block] [PATCH v3 07/44] block: Default .bdrv_child_perm() for form
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PATCH v3 07/44] block: Default .bdrv_child_perm() for format drivers |
Date: |
Tue, 28 Feb 2017 13:53:52 +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 | 44 ++++++++++++++++++++++++++++++++++++++++++++
include/block/block_int.h | 8 ++++++++
2 files changed, 52 insertions(+)
diff --git a/block.c b/block.c
index 064e9d7..d67819f 100644
--- a/block.c
+++ b/block.c
@@ -1560,6 +1560,50 @@ 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 and resizable backing file. */
+ /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */
+ if (shared & BLK_PERM_WRITE) {
+ shared = BLK_PERM_WRITE | BLK_PERM_RESIZE;
+ } else {
+ shared = 0;
+ }
+
+ 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,
bool check_new_perm)
{
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 17f4c2d..eb0598e 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -880,6 +880,14 @@ 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-block] [PATCH v3 00/44] New op blocker system, part 1, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 01/44] block: Add op blocker permission constants, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 03/44] block: Let callers request permissions when attaching a child node, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 02/44] block: Add Error argument to bdrv_attach_child(), Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 04/44] block: Involve block drivers in permission granting, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 05/44] block: Default .bdrv_child_perm() for filter drivers, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 06/44] block: Request child permissions in filter drivers, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 07/44] block: Default .bdrv_child_perm() for format drivers,
Kevin Wolf <=
- [Qemu-block] [PATCH v3 08/44] block: Request child permissions in format drivers, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 09/44] vvfat: Implement .bdrv_child_perm(), Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 11/44] block: Request real permissions in bdrv_attach_child(), Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 10/44] block: Require .bdrv_child_perm() with child nodes, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 12/44] block: Add permissions to BlockBackend, Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 13/44] block: Add permissions to blk_new(), Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 14/44] block: Add error parameter to blk_insert_bs(), Kevin Wolf, 2017/02/28
- [Qemu-block] [PATCH v3 15/44] block: Add BDRV_O_RESIZE for blk_new_open(), Kevin Wolf, 2017/02/28