alloc_vmap_area() currently assumes that sleeping is allowed during
allocation. This is not true for callers which pass non-blocking
GFP flags, such as GFP_ATOMIC or GFP_NOWAIT.
This patch adds logic to detect whether the given gfp_mask permits
blocking. It avoids invoking might_sleep() or falling back to reclaim
path if blocking is not allowed.
This makes alloc_vmap_area() safer for use in non-sleeping contexts,
where previously it could hit unexpected sleeps, trigger warnings.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
mm/vmalloc.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 6dbcdceecae1..81b6d3bde719 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
unsigned long freed;
unsigned long addr;
unsigned int vn_id;
+ bool allow_block;
int purged = 0;
int ret;
@@ -2026,7 +2027,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
if (unlikely(!vmap_initialized))
return ERR_PTR(-EBUSY);
- might_sleep();
+ allow_block = gfpflags_allow_blocking(gfp_mask);
+ might_sleep_if(allow_block);
/*
* If a VA is obtained from a global heap(if it fails here)
@@ -2065,8 +2067,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
* If an allocation fails, the error value is
* returned. Therefore trigger the overflow path.
*/
- if (IS_ERR_VALUE(addr))
- goto overflow;
+ if (IS_ERR_VALUE(addr)) {
+ if (allow_block)
+ goto overflow;
+
+ /*
+ * We can not trigger any reclaim logic because
+ * sleeping is not allowed, thus fail an allocation.
+ */
+ goto error;
+ }
va->va_start = addr;
va->va_end = addr + size;
@@ -2116,6 +2126,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
size, vstart, vend);
+error:
kmem_cache_free(vmap_area_cachep, va);
return ERR_PTR(-EBUSY);
}
--
2.39.5On 08/07/25 at 09:58am, Uladzislau Rezki (Sony) wrote:
> alloc_vmap_area() currently assumes that sleeping is allowed during
> allocation. This is not true for callers which pass non-blocking
> GFP flags, such as GFP_ATOMIC or GFP_NOWAIT.
>
> This patch adds logic to detect whether the given gfp_mask permits
> blocking. It avoids invoking might_sleep() or falling back to reclaim
> path if blocking is not allowed.
>
> This makes alloc_vmap_area() safer for use in non-sleeping contexts,
> where previously it could hit unexpected sleeps, trigger warnings.
>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
> mm/vmalloc.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
LGTM,
Reviewed-by: Baoquan He <bhe@redhat.com>
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6dbcdceecae1..81b6d3bde719 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> unsigned long freed;
> unsigned long addr;
> unsigned int vn_id;
> + bool allow_block;
> int purged = 0;
> int ret;
>
> @@ -2026,7 +2027,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> if (unlikely(!vmap_initialized))
> return ERR_PTR(-EBUSY);
>
> - might_sleep();
> + allow_block = gfpflags_allow_blocking(gfp_mask);
> + might_sleep_if(allow_block);
>
> /*
> * If a VA is obtained from a global heap(if it fails here)
> @@ -2065,8 +2067,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> * If an allocation fails, the error value is
> * returned. Therefore trigger the overflow path.
> */
> - if (IS_ERR_VALUE(addr))
> - goto overflow;
> + if (IS_ERR_VALUE(addr)) {
> + if (allow_block)
> + goto overflow;
> +
> + /*
> + * We can not trigger any reclaim logic because
> + * sleeping is not allowed, thus fail an allocation.
> + */
> + goto error;
> + }
>
> va->va_start = addr;
> va->va_end = addr + size;
> @@ -2116,6 +2126,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
> size, vstart, vend);
>
> +error:
> kmem_cache_free(vmap_area_cachep, va);
> return ERR_PTR(-EBUSY);
> }
> --
> 2.39.5
>
On Thu 07-08-25 09:58:05, Uladzislau Rezki wrote:
> alloc_vmap_area() currently assumes that sleeping is allowed during
> allocation. This is not true for callers which pass non-blocking
> GFP flags, such as GFP_ATOMIC or GFP_NOWAIT.
Those are currently not allowed so it would be better to mention this is
a preparation for those to _be_ supported later in the series.
> This patch adds logic to detect whether the given gfp_mask permits
> blocking. It avoids invoking might_sleep() or falling back to reclaim
> path if blocking is not allowed.
>
> This makes alloc_vmap_area() safer for use in non-sleeping contexts,
> where previously it could hit unexpected sleeps, trigger warnings.
>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
With the changelog clarified
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
> ---
> mm/vmalloc.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6dbcdceecae1..81b6d3bde719 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> unsigned long freed;
> unsigned long addr;
> unsigned int vn_id;
> + bool allow_block;
> int purged = 0;
> int ret;
>
> @@ -2026,7 +2027,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> if (unlikely(!vmap_initialized))
> return ERR_PTR(-EBUSY);
>
> - might_sleep();
> + allow_block = gfpflags_allow_blocking(gfp_mask);
> + might_sleep_if(allow_block);
>
> /*
> * If a VA is obtained from a global heap(if it fails here)
> @@ -2065,8 +2067,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> * If an allocation fails, the error value is
> * returned. Therefore trigger the overflow path.
> */
> - if (IS_ERR_VALUE(addr))
> - goto overflow;
> + if (IS_ERR_VALUE(addr)) {
> + if (allow_block)
> + goto overflow;
> +
> + /*
> + * We can not trigger any reclaim logic because
> + * sleeping is not allowed, thus fail an allocation.
> + */
> + goto error;
> + }
>
> va->va_start = addr;
> va->va_end = addr + size;
> @@ -2116,6 +2126,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
> size, vstart, vend);
>
> +error:
> kmem_cache_free(vmap_area_cachep, va);
> return ERR_PTR(-EBUSY);
> }
> --
> 2.39.5
--
Michal Hocko
SUSE Labs
On Thu, Aug 07, 2025 at 01:20:54PM +0200, Michal Hocko wrote: > On Thu 07-08-25 09:58:05, Uladzislau Rezki wrote: > > alloc_vmap_area() currently assumes that sleeping is allowed during > > allocation. This is not true for callers which pass non-blocking > > GFP flags, such as GFP_ATOMIC or GFP_NOWAIT. > > Those are currently not allowed so it would be better to mention this is > a preparation for those to _be_ supported later in the series. > > > This patch adds logic to detect whether the given gfp_mask permits > > blocking. It avoids invoking might_sleep() or falling back to reclaim > > path if blocking is not allowed. > > > > This makes alloc_vmap_area() safer for use in non-sleeping contexts, > > where previously it could hit unexpected sleeps, trigger warnings. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > With the changelog clarified > Acked-by: Michal Hocko <mhocko@suse.com> > Thanks! > Thank you! Added in the end: It is a preparation and adjustment step to later allow both GFP_ATOMIC and GFP_NOWAIT allocations in this series. -- Uladzislau Rezki
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