Re: [PATCH 09/11] ntfs: skip reads for full compression unit overwrites

2026=EB=85=84 7=EC=9B=94 21=EC=9D=BC (=ED=99=94) =EC=98=A4=ED=9B=84 6:55, N=
amjae Jeon <[email protected]>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> ntfs_compress_write() reads every page in a compression unit before copyi=
ng
> new data into it. The read is unnecessary when an aligned write replaces
> every byte covered by the page-cache folios.
>
> Detect full page-aligned compression unit overwrites and grab locked cach=
e
> folios without reading them. Keep the read-modify-write path for partial
> units and units that cover only part of a large page.
>
> Signed-off-by: Namjae Jeon <[email protected]>

Looks good to me.

Reviewed-by: Hyunchul Lee <[email protected]>

> ---
>  fs/ntfs/compress.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ntfs/compress.c b/fs/ntfs/compress.c
> index a3af669b1008..ea29fade9b9b 100644
> --- a/fs/ntfs/compress.c
> +++ b/fs/ntfs/compress.c
> @@ -1501,6 +1501,7 @@ int ntfs_compress_write(struct ntfs_inode *ni, loff=
_t pos, size_t count,
>                 pgoff_t index;
>                 size_t copied, bytes;
>                 unsigned int page_offset;
> +               bool full_cb;
>                 int off;
>
>                 off =3D pos & (cb_size - 1);
> @@ -1512,6 +1513,8 @@ int ntfs_compress_write(struct ntfs_inode *ni, loff=
_t pos, size_t count,
>                 page_offset =3D offset_in_page(cb_off);
>                 pages_per_cb =3D DIV_ROUND_UP(page_offset + cb_size, PAGE=
_SIZE);
>                 index =3D cb_off >> PAGE_SHIFT;
> +               full_cb =3D !off && bytes =3D=3D cb_size && !page_offset =
&&
> +                               !(cb_size & (PAGE_SIZE - 1));
>
>                 if (unlikely(fault_in_iov_iter_readable(from, bytes))) {
>                         err =3D -EFAULT;
> @@ -1519,7 +1522,10 @@ int ntfs_compress_write(struct ntfs_inode *ni, lof=
f_t pos, size_t count,
>                 }
>
>                 for (i =3D 0; i < pages_per_cb; i++) {
> -                       folio =3D read_mapping_folio(mapping, index + i, =
NULL);
> +                       if (full_cb)
> +                               folio =3D filemap_grab_folio(mapping, ind=
ex + i);
> +                       else
> +                               folio =3D read_mapping_folio(mapping, ind=
ex + i, NULL);
>                         if (IS_ERR(folio)) {
>                                 for (ip =3D 0; ip < i; ip++) {
>                                         folio_unlock(page_folio(pages[ip]=
));
> @@ -1529,7 +1535,8 @@ int ntfs_compress_write(struct ntfs_inode *ni, loff=
_t pos, size_t count,
>                                 goto out;
>                         }
>
> -                       folio_lock(folio);
> +                       if (!full_cb)
> +                               folio_lock(folio);
>                         pages[i] =3D folio_page(folio, 0);
>                 }
>
> --
> 2.34.1
>


--=20
Thanks,
Hyunchul