[v3,17/25] gup: Don't allow FOLL_LONGTERM pinning of FS DAX pages

Commit Message

Alistair Popple Nov. 22, 2024, 1:40 a.m. UTC

Longterm pinning of FS DAX pages should already be disallowed by
various pXX_devmap checks. However a future change will cause these
checks to be invalid for FS DAX pages so make
folio_is_longterm_pinnable() return false for FS DAX pages.

Signed-off-by: Alistair Popple <[e-mail]>
---
 include/linux/mm.h | 4 ++++
 1 file changed, 4 insertions(+)

Comments

John Hubbard Nov. 22, 2024, 3:23 a.m. UTC | #1

On 11/21/24 5:40 PM, Alistair Popple wrote:
> Longterm pinning of FS DAX pages should already be disallowed by
> various pXX_devmap checks. However a future change will cause these
> checks to be invalid for FS DAX pages so make
> folio_is_longterm_pinnable() return false for FS DAX pages.
> 
> Signed-off-by: Alistair Popple <[e-mail]>
> ---
>   include/linux/mm.h | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 22c651b..4f9ae37 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2004,6 +2004,10 @@ static inline bool folio_is_longterm_pinnable(struct folio *folio)
>   	if (folio_is_device_coherent(folio))
>   		return false;
>   
> +	/* DAX must also always allow eviction. */
> +	if (folio_is_fsdax(folio))
> +		return false;
> +
>   	/* Otherwise, non-movable zone folios can be pinned. */
>   	return !folio_is_zone_movable(folio);
>   

Reviewed-by: John Hubbard <[e-mail]>


thanks,

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 22c651b..4f9ae37 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2004,6 +2004,10 @@  static inline bool folio_is_longterm_pinnable(struct folio *folio)
 	if (folio_is_device_coherent(folio))
 		return false;
 
+	/* DAX must also always allow eviction. */
+	if (folio_is_fsdax(folio))
+		return false;
+
 	/* Otherwise, non-movable zone folios can be pinned. */
 	return !folio_is_zone_movable(folio);