[PATCH] drm/ttm: Convert -EAGAIN from dmem_cgroup_try_charge to -ENOSPC

[PATCH] drm/ttm: Convert -EAGAIN from dmem_cgroup_try_charge to -ENOSPC

[Thomas Hellström]

dmem_cgroup_try_charge() returns -EAGAIN when the cgroup limit is
hit and the charge fails. TTM has no concept of -EAGAIN from resource
allocation; -ENOSPC is the canonical error meaning "no space, try
eviction". Convert at the source in ttm_resource_alloc() so no caller
needs to handle an unexpected error code, and clean up the now-redundant
-EAGAIN check in ttm_bo_alloc_resource().

Without this, -EAGAIN escaping ttm_resource_alloc() during an eviction
walk causes the walk to terminate early instead of continuing to the
next candidate.

Cc: Friedrich Vock <friedrich.vock@gmx.de>
Cc: Maarten Lankhorst <dev@lankhorst.se>
Cc: Tejun Heo <tj@kernel.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.14+
Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c       | 2 +-
 drivers/gpu/drm/ttm/ttm_resource.c | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index d85f0a37ac35..cee3828df655 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -739,7 +739,7 @@ static int ttm_bo_alloc_resource(struct ttm_buffer_object *bo,
 		may_evict = (force_space && place->mem_type != TTM_PL_SYSTEM);
 		ret = ttm_resource_alloc(bo, place, res, force_space ? &limit_pool : NULL);
 		if (ret) {
-			if (ret != -ENOSPC && ret != -EAGAIN) {
+			if (ret != -ENOSPC) {
 				dmem_cgroup_pool_state_put(limit_pool);
 				return ret;
 			}
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 9f36631d48b6..b0efffe5a526 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -385,8 +385,11 @@ int ttm_resource_alloc(struct ttm_buffer_object *bo,
 
 	if (man->cg) {
 		ret = dmem_cgroup_try_charge(man->cg, bo->base.size, &pool, ret_limit_pool);
-		if (ret)
+		if (ret) {
+			if (ret == -EAGAIN)
+				ret = -ENOSPC;
 			return ret;
+		}
 	}
 
 	ret = man->func->alloc(man, bo, place, res_ptr);
-- 
2.54.0

Re: [PATCH] drm/ttm: Convert -EAGAIN from dmem_cgroup_try_charge to -ENOSPC

[Maarten Lankhorst]

Hey,

Den 2026-05-08 kl. 18:09, skrev Thomas Hellström:
> dmem_cgroup_try_charge() returns -EAGAIN when the cgroup limit is
> hit and the charge fails. TTM has no concept of -EAGAIN from resource
> allocation; -ENOSPC is the canonical error meaning "no space, try
> eviction". Convert at the source in ttm_resource_alloc() so no caller
> needs to handle an unexpected error code, and clean up the now-redundant
> -EAGAIN check in ttm_bo_alloc_resource().
> 
> Without this, -EAGAIN escaping ttm_resource_alloc() during an eviction
> walk causes the walk to terminate early instead of continuing to the
> next candidate.
> 
> Cc: Friedrich Vock <friedrich.vock@gmx.de>
> Cc: Maarten Lankhorst <dev@lankhorst.se>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Christian Koenig <christian.koenig@amd.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v6.14+
> Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
> Assisted-by: GitHub_Copilot:claude-sonnet-4.6
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c       | 2 +-
>  drivers/gpu/drm/ttm/ttm_resource.c | 5 ++++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index d85f0a37ac35..cee3828df655 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -739,7 +739,7 @@ static int ttm_bo_alloc_resource(struct ttm_buffer_object *bo,
>  		may_evict = (force_space && place->mem_type != TTM_PL_SYSTEM);
>  		ret = ttm_resource_alloc(bo, place, res, force_space ? &limit_pool : NULL);
>  		if (ret) {
> -			if (ret != -ENOSPC && ret != -EAGAIN) {
> +			if (ret != -ENOSPC) {
>  				dmem_cgroup_pool_state_put(limit_pool);
>  				return ret;
>  			}
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index 9f36631d48b6..b0efffe5a526 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -385,8 +385,11 @@ int ttm_resource_alloc(struct ttm_buffer_object *bo,
>  
>  	if (man->cg) {
>  		ret = dmem_cgroup_try_charge(man->cg, bo->base.size, &pool, ret_limit_pool);
> -		if (ret)
> +		if (ret) {
> +			if (ret == -EAGAIN)
> +				ret = -ENOSPC;
>  			return ret;
> +		}
>  	}
>  
>  	ret = man->func->alloc(man, bo, place, res_ptr);

Yeah looks reasonable with the conversion to callbacks.

Reviewed-by: Maarten Lankhorst <dev@lankhrost.se>

Re: [PATCH] drm/ttm: Convert -EAGAIN from dmem_cgroup_try_charge to -ENOSPC

[Thomas Hellström]

On Fri, 2026-05-08 at 19:03 +0200, Maarten Lankhorst wrote:
> Hey,
> 
> Den 2026-05-08 kl. 18:09, skrev Thomas Hellström:
> > dmem_cgroup_try_charge() returns -EAGAIN when the cgroup limit is
> > hit and the charge fails. TTM has no concept of -EAGAIN from
> > resource
> > allocation; -ENOSPC is the canonical error meaning "no space, try
> > eviction". Convert at the source in ttm_resource_alloc() so no
> > caller
> > needs to handle an unexpected error code, and clean up the now-
> > redundant
> > -EAGAIN check in ttm_bo_alloc_resource().
> > 
> > Without this, -EAGAIN escaping ttm_resource_alloc() during an
> > eviction
> > walk causes the walk to terminate early instead of continuing to
> > the
> > next candidate.
> > 
> > Cc: Friedrich Vock <friedrich.vock@gmx.de>
> > Cc: Maarten Lankhorst <dev@lankhorst.se>
> > Cc: Tejun Heo <tj@kernel.org>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Christian Koenig <christian.koenig@amd.com>
> > Cc: dri-devel@lists.freedesktop.org
> > Cc: <stable@vger.kernel.org> # v6.14+
> > Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in
> > TTM")
> > Assisted-by: GitHub_Copilot:claude-sonnet-4.6
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > ---
> >  drivers/gpu/drm/ttm/ttm_bo.c       | 2 +-
> >  drivers/gpu/drm/ttm/ttm_resource.c | 5 ++++-
> >  2 files changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> > b/drivers/gpu/drm/ttm/ttm_bo.c
> > index d85f0a37ac35..cee3828df655 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -739,7 +739,7 @@ static int ttm_bo_alloc_resource(struct
> > ttm_buffer_object *bo,
> >  		may_evict = (force_space && place->mem_type !=
> > TTM_PL_SYSTEM);
> >  		ret = ttm_resource_alloc(bo, place, res,
> > force_space ? &limit_pool : NULL);
> >  		if (ret) {
> > -			if (ret != -ENOSPC && ret != -EAGAIN) {
> > +			if (ret != -ENOSPC) {
> >  				dmem_cgroup_pool_state_put(limit_p
> > ool);
> >  				return ret;
> >  			}
> > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > b/drivers/gpu/drm/ttm/ttm_resource.c
> > index 9f36631d48b6..b0efffe5a526 100644
> > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > @@ -385,8 +385,11 @@ int ttm_resource_alloc(struct
> > ttm_buffer_object *bo,
> >  
> >  	if (man->cg) {
> >  		ret = dmem_cgroup_try_charge(man->cg, bo-
> > >base.size, &pool, ret_limit_pool);
> > -		if (ret)
> > +		if (ret) {
> > +			if (ret == -EAGAIN)
> > +				ret = -ENOSPC;
> >  			return ret;
> > +		}
> >  	}
> >  
> >  	ret = man->func->alloc(man, bo, place, res_ptr);
> 
> Yeah looks reasonable with the conversion to callbacks.
> 
> Reviewed-by: Maarten Lankhorst <dev@lankhrost.se>

Thanks for reviewing, Maarten! 

@Christian, any concerns?

/Thomas