illumos gate

debug kernels panic with the message:

assertion failed: dbu->dbu_evict_func == NULL

The stack is:

fffffffffbc7fca0 zfs`sa_handle_get_from_db+0x143(ffffff00a63ff540,
ffffff00a65f7c68, ffffff00a6655e90, 0, ffffff00a6655f78)
fffffffffbc7fd20 zfs`zfs_znode_sa_init+0x179(ffffff00a5b95000, ffffff00a6655e90
, ffffff00a65f7c68, 2c, 0)
fffffffffbc7ff20 zfs`zfs_znode_alloc+0xdc(ffffff00a5b95000, ffffff00a65f7c68,
800, 2c, 0)
fffffffffbc7ffd0 zfs`zfs_zget+0x101(ffffff00a5b95000, 4, fffffffffbc7ffe8)
fffffffffbc80020 zfs`zfs_mountroot+0x163(fffffffffbff3da0, 0)
fffffffffbc80040 fsop_mountroot+0x17(fffffffffbff3da0, 0)
fffffffffbc80070 rootconf+0x12d()
fffffffffbc800b0 vfs_mountroot+0x6f()
fffffffffbc800f0 main+0x198()
fffffffffbc80100 _locore_start+0x90()

(the assert is via the inlined and thus invisible (which really gets my goat, fwiw) dmu_buf_init_user)

This code violates the invariant spelled out in kmem_cache_create(9F) that upon freeing an object with kmem_cache_free() it must be "in its constructed state", thus the handle we get from kmem_cache_alloc in the NULL case of sa_handle_get_from_db() might not be in its constructed state, and thus will fail the NULL assertion.

In my case, this causes us to panic when mounting /.