Launch QEMU with

  $ qemu-img create \
      --object secret,id=sec0,data=123456 \
      -f luks -o key-secret=sec0 demo.luks 1g

  $ qemu-system-x86_64 \
      --object secret,id=sec0,data=123456 \
      -blockdev  driver=luks,key-secret=sec0,file.filename=demo.luks,file.driver=file,node-name=luks

Then in QMP shell attempt

  x-blockdev-amend job-id=fish node-name=luks options={'state':'active','new-secret':'sec0','driver':'luks'}

It will result in an assertion

  #0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
  #1  0x00007fad18b73f63 in __pthread_kill_internal (threadid=<optimized out>, signo=6) at pthread_kill.c:89
  #2  0x00007fad18b19f3e in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
  #3  0x00007fad18b016d0 in __GI_abort () at abort.c:77
  #4  0x00007fad18b01639 in __assert_fail_base
      (fmt=<optimized out>, assertion=<optimized out>, file=<optimized out>, line=<optimized out>, function=<optimized out>) at assert.c:118
  #5  0x00007fad18b120af in __assert_fail (assertion=<optimized out>, file=<optimized out>, line=<optimized out>, function=<optimized out>)
      at assert.c:127
  #6  0x000055ff74fdbd46 in bdrv_graph_rdlock_main_loop () at ../block/graph-lock.c:260
  #7  0x000055ff7548521b in graph_lockable_auto_lock_mainloop (x=<optimized out>)
      at /usr/src/debug/qemu-9.2.4-1.fc42.x86_64/include/block/graph-lock.h:266
  #8  block_crypto_read_func (block=<optimized out>, offset=4096, buf=0x55ffb6d66ef0 "", buflen=256000, opaque=0x55ffb5edcc30, errp=0x55ffb6f00700)
      at ../block/crypto.c:71
  #9  0x000055ff75439f8b in qcrypto_block_luks_load_key
      (block=block@entry=0x55ffb5edbe90, slot_idx=slot_idx@entry=0, password=password@entry=0x55ffb67dc260 "123456", masterkey=masterkey@entry=0x55ffb5fb0c40 "", readfunc=readfunc@entry=0x55ff754851e0 <block_crypto_read_func>, opaque=opaque@entry=0x55ffb5edcc30, errp=0x55ffb6f00700)
      at ../crypto/block-luks.c:927
  #10 0x000055ff7543b90f in qcrypto_block_luks_find_key
      (block=<optimized out>, password=<optimized out>, masterkey=<optimized out>, readfunc=<optimized out>, opaque=<optimized out>, errp=<optimized out>) at ../crypto/block-luks.c:1045
  #11 qcrypto_block_luks_amend_add_keyslot
      (block=0x55ffb5edbe90, readfunc=0x55ff754851e0 <block_crypto_read_func>, writefunc=0x55ff75485100 <block_crypto_write_func>, opaque=0x55ffb5edcc3, opts_luks=0x7fad1715aef8, force=<optimized out>, errp=0x55ffb6f00700) at ../crypto/block-luks.c:1673
  #12 qcrypto_block_luks_amend_options
      (block=0x55ffb5edbe90, readfunc=0x55ff754851e0 <block_crypto_read_func>, writefunc=0x55ff75485100 <block_crypto_write_func>, opaque=0x55ffb5edcc30, options=0x7fad1715aef0, force=<optimized out>, errp=0x55ffb6f00700) at ../crypto/block-luks.c:1865
  #13 0x000055ff75485b95 in block_crypto_amend_options_generic_luks
      (bs=<optimized out>, amend_options=<optimized out>, force=<optimized out>, errp=<optimized out>) at ../block/crypto.c:949
  #14 0x000055ff75485c28 in block_crypto_co_amend_luks (bs=<optimized out>, opts=<optimized out>, force=<optimized out>, errp=<optimized out>)
      at ../block/crypto.c:1008
  #15 0x000055ff754778e5 in blockdev_amend_run (job=0x55ffb6f00640, errp=0x55ffb6f00700) at ../block/amend.c:52
  #16 0x000055ff75468b90 in job_co_entry (opaque=0x55ffb6f00640) at ../job.c:1106
  #17 0x000055ff755a0fc2 in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at ../util/coroutine-ucontext.c:175

This changes the read/write callbacks to not assert that they
are run in mainloop context if already in a coroutine.

Fixes: 1f051dcbdf2e4b6f518db731c84e304b2b9d15ce
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---

I'm not really sure if this is correct or not, as the docs on the
graph lock usage are not very clear on what I should be doing.

Also I'm wondering if qcow2.c needs work too. When 1f051dc added
the GRAPH_RDLOCK_GUARD_MAINLOOP in read_func/write_func for the
crypto.c file, it did not do the same with the read_func/write_func
for the qcow2.c file, despite them being used from the same call
paths AFAICT (both image creation & amend).

 block/crypto.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/block/crypto.c b/block/crypto.c
index d4226cc68a..a1f8d24df1 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -67,11 +67,18 @@ static int block_crypto_read_func(QCryptoBlock *block,
     BlockCrypto *crypto = bs->opaque;
     ssize_t ret;
 
-    GLOBAL_STATE_CODE();
-    GRAPH_RDLOCK_GUARD_MAINLOOP();
+    if (qemu_in_coroutine()) {
+        GRAPH_RDLOCK_GUARD();
 
-    ret = bdrv_pread(crypto->header ? crypto->header : bs->file,
-                     offset, buflen, buf, 0);
+        ret = bdrv_co_pread(crypto->header ? crypto->header : bs->file,
+                            offset, buflen, buf, 0);
+    } else {
+        GLOBAL_STATE_CODE();
+        GRAPH_RDLOCK_GUARD_MAINLOOP();
+
+        ret = bdrv_pread(crypto->header ? crypto->header : bs->file,
+                         offset, buflen, buf, 0);
+    }
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Could not read encryption header");
         return ret;
@@ -90,11 +97,18 @@ static int block_crypto_write_func(QCryptoBlock *block,
     BlockCrypto *crypto = bs->opaque;
     ssize_t ret;
 
-    GLOBAL_STATE_CODE();
-    GRAPH_RDLOCK_GUARD_MAINLOOP();
+    if (qemu_in_coroutine()) {
+        GRAPH_RDLOCK_GUARD();
 
-    ret = bdrv_pwrite(crypto->header ? crypto->header : bs->file,
-                      offset, buflen, buf, 0);
+        ret = bdrv_co_pwrite(crypto->header ? crypto->header : bs->file,
+                             offset, buflen, buf, 0);
+    } else {
+        GLOBAL_STATE_CODE();
+        GRAPH_RDLOCK_GUARD_MAINLOOP();
+
+        ret = bdrv_pwrite(crypto->header ? crypto->header : bs->file,
+                          offset, buflen, buf, 0);
+    }
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Could not write encryption header");
         return ret;
-- 
2.50.1