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qemu-io: Drop write permissions before read-only reopen

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qemu-io provides a 'reopen' command that allows switching from writable
to read-only access. We need to make sure that we don't try to keep
write permissions to a BlockBackend that becomes read-only, otherwise
things are going to fail.

This requires a bdrv_drain() call because otherwise in-flight AIO
write requests could issue new internal requests while the permission
has already gone away, which would cause assertion failures. Draining
the queue doesn't break AIO requests in any new way, bdrv_reopen() would
drain it anyway only a few lines later.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Kevin Wolf 2017-09-22 14:50:12 +02:00
parent 7a6ab45e19
commit f3adefb2ce
2 changed files with 13 additions and 1 deletions
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12
qemu-io-cmds.c
View File

@ -2010,6 +2010,18 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
return 0;
}
if (!(flags & BDRV_O_RDWR)) {
uint64_t orig_perm, orig_shared_perm;
bdrv_drain(bs);
blk_get_perm(blk, &orig_perm, &orig_shared_perm);
blk_set_perm(blk,
orig_perm & ~(BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED),
orig_shared_perm,
&error_abort);
}
qopts = qemu_opts_find(&reopen_opts, NULL);
opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
qemu_opts_reset(&reopen_opts);

2
tests/qemu-iotests/187.out
View File

@ -12,7 +12,7 @@ Start from read-write
wrote 65536/65536 bytes at offset 0
64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
write failed: Operation not permitted
Block node is read-only
wrote 65536/65536 bytes at offset 0
64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
*** done