Re: [PATCH] f2fs: Use mapping->gfp_mask to get file cache for writing

Chao Yu
2025-09-24T02:25:19Z

On 9/18/25 11:32, Jiucheng Xu via B4 Relay wrote:
> From: Jiucheng Xu <jiucheng.xu@amlogic.com>
>
> On 32-bit architectures, when GFP_NOFS is used, the file cache for write
> operations cannot be allocated from the highmem and CMA.

Hi,

Have you suffered any problem w/o this patch? Can you please describe more
details about it?

>
> Since mapping->gfp_mask is set to GFP_HIGHUSER_MOVABLE during inode

GFP_HIGHUSER_MOVABLE includes __GFP_FS, we should avoid using __GFP_FS here.
f2fs_write_begin() uses GFP_NOFS like the most of other filesystem to avoid
potential deadlock, as __filemap_get_folio(, .. |__GFP_FS | ..) may run into
memory reclaim to call ->writeback in where we may suffer deadlock potentially.

Thanks,

> allocation, using mapping_gfp_mask(mapping) as the GFP flag of getting file
> cache for writing is more efficient for 32-bit architectures.
> > Signed-off-by: Jiucheng Xu <jiucheng.xu@amlogic.com>
> ---
> fs/f2fs/data.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 7961e0ddfca3aaa332b7dbd4985ae7766551834f..9fbc41f9accb2626da22754f1a424da4805ca823 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3587,7 +3587,8 @@ static int f2fs_write_begin(const struct kiocb *iocb,
> * Will wait that below with our IO control.
> */
> folio = __filemap_get_folio(mapping, index,
> - FGP_LOCK | FGP_WRITE | FGP_CREAT, GFP_NOFS);
> + FGP_LOCK | FGP_WRITE | FGP_CREAT,
> + mapping_gfp_mask(mapping));
> if (IS_ERR(folio)) {
> err = PTR_ERR(folio);
> goto fail;
>
> ---
> base-commit: c872b6279cd26762339ff02513e2a3f16149a6f1
> change-id: 20250910-origin-dev-8a5ff6bee1f2
>
> Best regards,