drm/ttm: Hook up a cgroup-aware reclaim callback for the dmem controller

Add ttm_bo_evict_cgroup() to evict buffer objects charged to a specific
dmem cgroup pool from a resource manager's LRU until a byte target is
met.  Add ttm_resource_manager_set_dmem_region() to associate a dmem
cgroup region with a resource manager; drivers supply their own
dmem_cgroup_ops with ttm_resource_manager_dmem_reclaim as the reclaim
function and the manager pointer as reclaim_priv in the dmem_cgroup_init
to wire up TTM eviction as the reclaim callback.

The eviction context is interruptible; signals abort the operation and
propagate back through the write() syscall.

Introduce a new mode for the bo LRU walker so that sleeping locks
can be taken. This can be used when the caller doesn't hold any
previous dma_resv locks, and where it intends to hold at most
one lock at a time.

Like the rest of the TTM eviction this should sooner than later
be converted to full WW transactions.

v3:
- Fix ttm_resource_manager_set_dmem_region() storing an error pointer
  in man->cg unconditionally. (Sashiko-bot)
- Fix kernel-doc function name format for ttm_bo_evict_cgroup() and
  ttm_resource_manager_set_dmem_region().

v5:
- Rebased on the introduction of struct dmem_cgroup_init.
- Handle NULL region in ttm_resource_manager_set_dmem_region() to clear
  the reclaim callback, preventing use-after-free when the manager is
  torn down while the dmem region outlives it. (Sashiko-bot)
- Return 0 on any progress (even partial eviction), -ENOSPC only when
  nothing was freed; fixes callers that expected 0 on partial success.
- Document that the reclaim callback should return 0 if some progress
  was made, -ENOSPC if no progress at all, or another error for fatal
  failures.

v8:
- Fix ttm_resource_manager_set_dmem_region() using IS_ERR_OR_NULL(),
  which skipped the assignment for a NULL region and thus never
  cleared man->cg. Use IS_ERR() so that a NULL region detaches the
  region as the kernel-doc and the v5 changelog intended. (Sashiko-bot)

v9:
- Don't leak cgroup charges for bos that may have survived dmemcg
  region fini.
- Drop the misleading "Capture size before eviction in case res is
  cleared" comment in ttm_bo_evict_cb(). (Maarten Lankhorst)

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> #v7
Tested-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://patch.msgid.link/20260725100036.2372-5-thomas.hellstrom@linux.intel.com
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

0 files changed, 0 insertions, 0 deletions