From 35806318c04a6d8450ed745d1921a07915c3cc16 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Mon, 4 Dec 2017 12:10:03 +0100
Subject: [PATCH 32/36] block: Base permissions on rw state after reopen

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20171204121007.12964-5-kwolf@redhat.com>
Patchwork-id: 78109
O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH v2 4/8] block: Base permissions on rw state after reopen
Bugzilla: 1492178
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

When new permissions are calculated during bdrv_reopen(), they need to
be based on the state of the graph as it will be after the reopen has
completed, not on the current state of the involved nodes.

This patch makes bdrv_is_writable() optionally accept a BlockReopenQueue
from which the new flags are taken. This is then used for determining
the new bs->file permissions of format drivers as soon as we add the
code to actually pass a non-NULL reopen queue to the .bdrv_child_perm
callbacks.

While moving bdrv_is_writable(), make it static. It isn't used outside
block.c.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 148eb13c84cccd0eedd6e59f90e0151bd7bac9fa)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c               | 52 ++++++++++++++++++++++++++++++++++++---------------
 include/block/block.h |  1 -
 2 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/block.c b/block.c
index 5ce773a..5cce274 100644
--- a/block.c
+++ b/block.c
@@ -240,12 +240,6 @@ bool bdrv_is_read_only(BlockDriverState *bs)
     return bs->read_only;
 }
 
-/* Returns whether the image file can be written to right now */
-bool bdrv_is_writable(BlockDriverState *bs)
-{
-    return !bdrv_is_read_only(bs) && !(bs->open_flags & BDRV_O_INACTIVE);
-}
-
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
                            bool ignore_allow_rdw, Error **errp)
 {
@@ -1535,6 +1529,41 @@ static int bdrv_child_check_perm(BdrvChild *c, BlockReopenQueue *q,
 static void bdrv_child_abort_perm_update(BdrvChild *c);
 static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared);
 
+typedef struct BlockReopenQueueEntry {
+     bool prepared;
+     BDRVReopenState state;
+     QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry;
+} BlockReopenQueueEntry;
+
+/*
+ * Return the flags that @bs will have after the reopens in @q have
+ * successfully completed. If @q is NULL (or @bs is not contained in @q),
+ * return the current flags.
+ */
+static int bdrv_reopen_get_flags(BlockReopenQueue *q, BlockDriverState *bs)
+{
+    BlockReopenQueueEntry *entry;
+
+    if (q != NULL) {
+        QSIMPLEQ_FOREACH(entry, q, entry) {
+            if (entry->state.bs == bs) {
+                return entry->state.flags;
+            }
+        }
+    }
+
+    return bs->open_flags;
+}
+
+/* Returns whether the image file can be written to after the reopen queue @q
+ * has been successfully applied, or right now if @q is NULL. */
+static bool bdrv_is_writable(BlockDriverState *bs, BlockReopenQueue *q)
+{
+    int flags = bdrv_reopen_get_flags(q, bs);
+
+    return (flags & (BDRV_O_RDWR | BDRV_O_INACTIVE)) == BDRV_O_RDWR;
+}
+
 static void bdrv_child_perm(BlockDriverState *bs, BlockDriverState *child_bs,
                             BdrvChild *c, const BdrvChildRole *role,
                             BlockReopenQueue *reopen_queue,
@@ -1572,7 +1601,7 @@ static int bdrv_check_perm(BlockDriverState *bs, BlockReopenQueue *q,
 
     /* Write permissions never work with read-only images */
     if ((cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) &&
-        !bdrv_is_writable(bs))
+        !bdrv_is_writable(bs, q))
     {
         error_setg(errp, "Block node is read-only");
         return -EPERM;
@@ -1862,8 +1891,7 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
                                   &perm, &shared);
 
         /* Format drivers may touch metadata even if the guest doesn't write */
-        /* TODO Take flags from reopen_queue */
-        if (bdrv_is_writable(bs)) {
+        if (bdrv_is_writable(bs, reopen_queue)) {
             perm |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
         }
 
@@ -2641,12 +2669,6 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference,
                              NULL, errp);
 }
 
-typedef struct BlockReopenQueueEntry {
-     bool prepared;
-     BDRVReopenState state;
-     QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry;
-} BlockReopenQueueEntry;
-
 /*
  * Adds a BlockDriverState to a simple queue for an atomic, transactional
  * reopen of multiple devices.
diff --git a/include/block/block.h b/include/block/block.h
index ab80195..4d0d2da 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -435,7 +435,6 @@ int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
                             int64_t offset, int64_t bytes, int64_t *pnum);
 
 bool bdrv_is_read_only(BlockDriverState *bs);
-bool bdrv_is_writable(BlockDriverState *bs);
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
                            bool ignore_allow_rdw, Error **errp);
 int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp);
-- 
1.8.3.1