[PATCH v3] sched_ext: Use kvzalloc for large exit_dump allocation

[PATCH v3] sched_ext: Use kvzalloc for large exit_dump allocation

[Breno Leitao]

Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
can require large contiguous memory depending on the implementation.
This change prevents allocation failures by allowing the system to fall
back to vmalloc when contiguous memory allocation fails.

Since this buffer is only used for debugging purposes, physical memory
contiguity is not required, making vmalloc a suitable alternative.

Cc: stable@vger.kernel.org
Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
Suggested-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
---
Changes in v3:
- Rewording the patch message
- Link to v2: https://lore.kernel.org/r/20250408-scx-v2-1-1979fc040903@debian.org

Changes in v2:
- Use kvfree() on the free path as well.
- Link to v1: https://lore.kernel.org/r/20250407-scx-v1-1-774ba74a2c17@debian.org
---
 kernel/sched/ext.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 66bcd40a28ca1..db9af6a3c04fd 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4623,7 +4623,7 @@ static void scx_ops_bypass(bool bypass)
 
 static void free_exit_info(struct scx_exit_info *ei)
 {
-	kfree(ei->dump);
+	kvfree(ei->dump);
 	kfree(ei->msg);
 	kfree(ei->bt);
 	kfree(ei);
@@ -4639,7 +4639,7 @@ static struct scx_exit_info *alloc_exit_info(size_t exit_dump_len)
 
 	ei->bt = kcalloc(SCX_EXIT_BT_LEN, sizeof(ei->bt[0]), GFP_KERNEL);
 	ei->msg = kzalloc(SCX_EXIT_MSG_LEN, GFP_KERNEL);
-	ei->dump = kzalloc(exit_dump_len, GFP_KERNEL);
+	ei->dump = kvzalloc(exit_dump_len, GFP_KERNEL);
 
 	if (!ei->bt || !ei->msg || !ei->dump) {
 		free_exit_info(ei);

---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250407-scx-11dbf94803c3

Best regards,
-- 
Breno Leitao <leitao@debian.org>

Re: [PATCH v3] sched_ext: Use kvzalloc for large exit_dump allocation

[Andrea Righi]

On Tue, Apr 08, 2025 at 09:50:42AM -0700, Breno Leitao wrote:
> Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
> can require large contiguous memory depending on the implementation.
> This change prevents allocation failures by allowing the system to fall
> back to vmalloc when contiguous memory allocation fails.
> 
> Since this buffer is only used for debugging purposes, physical memory
> contiguity is not required, making vmalloc a suitable alternative.

Thanks for updating the description. LGTM!

-Andrea

> 
> Cc: stable@vger.kernel.org
> Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
> Suggested-by: Rik van Riel <riel@surriel.com>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Acked-by: Andrea Righi <arighi@nvidia.com>
> ---
> Changes in v3:
> - Rewording the patch message
> - Link to v2: https://lore.kernel.org/r/20250408-scx-v2-1-1979fc040903@debian.org
> 
> Changes in v2:
> - Use kvfree() on the free path as well.
> - Link to v1: https://lore.kernel.org/r/20250407-scx-v1-1-774ba74a2c17@debian.org
> ---
>  kernel/sched/ext.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 66bcd40a28ca1..db9af6a3c04fd 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -4623,7 +4623,7 @@ static void scx_ops_bypass(bool bypass)
>  
>  static void free_exit_info(struct scx_exit_info *ei)
>  {
> -	kfree(ei->dump);
> +	kvfree(ei->dump);
>  	kfree(ei->msg);
>  	kfree(ei->bt);
>  	kfree(ei);
> @@ -4639,7 +4639,7 @@ static struct scx_exit_info *alloc_exit_info(size_t exit_dump_len)
>  
>  	ei->bt = kcalloc(SCX_EXIT_BT_LEN, sizeof(ei->bt[0]), GFP_KERNEL);
>  	ei->msg = kzalloc(SCX_EXIT_MSG_LEN, GFP_KERNEL);
> -	ei->dump = kzalloc(exit_dump_len, GFP_KERNEL);
> +	ei->dump = kvzalloc(exit_dump_len, GFP_KERNEL);
>  
>  	if (!ei->bt || !ei->msg || !ei->dump) {
>  		free_exit_info(ei);
> 
> ---
> base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
> change-id: 20250407-scx-11dbf94803c3
> 
> Best regards,
> -- 
> Breno Leitao <leitao@debian.org>
> 

Re: [PATCH v3] sched_ext: Use kvzalloc for large exit_dump allocation

[Tejun Heo]

On Tue, Apr 08, 2025 at 09:50:42AM -0700, Breno Leitao wrote:
> Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
> can require large contiguous memory depending on the implementation.
> This change prevents allocation failures by allowing the system to fall
> back to vmalloc when contiguous memory allocation fails.
> 
> Since this buffer is only used for debugging purposes, physical memory
> contiguity is not required, making vmalloc a suitable alternative.
> 
> Cc: stable@vger.kernel.org
> Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
> Suggested-by: Rik van Riel <riel@surriel.com>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Acked-by: Andrea Righi <arighi@nvidia.com>

Applied to sched_ext/for-6.15-fixes.

Thanks.

-- 
tejun