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SubjectRe: [PATCH] erofs: remove unneeded icur field from struct z_erofs_decompress_frontend
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On 2023/4/17 14:41, Yue Hu wrote:
> From: Yue Hu <huyue2@coolpad.com>
>
> The icur field is only used in z_erofs_try_inplace_io(). Let's just use
> a local variable instead. And no need to check if the pcluster is inline
> when setting icur since inline page cannot be used for inplace I/O.
>
> Signed-off-by: Yue Hu <huyue2@coolpad.com>

Nope, it's a behavior change.
Other users could feed more inplace I/O pages before I/O submission
to reduce memory consumption, it's common when applying stress model
in low memory scenarios.

Thanks,
Gao Xiang

> ---
> fs/erofs/zdata.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index f759152feffa..f8bf2b227942 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -554,9 +554,6 @@ struct z_erofs_decompress_frontend {
> /* used for applying cache strategy on the fly */
> bool backmost;
> erofs_off_t headoffset;
> -
> - /* a pointer used to pick up inplace I/O pages */
> - unsigned int icur;
> };
>
> #define DECOMPRESS_FRONTEND_INIT(__i) { \
> @@ -707,11 +704,13 @@ static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
> struct z_erofs_bvec *bvec)
> {
> struct z_erofs_pcluster *const pcl = fe->pcl;
> + /* file-backed online pages are traversed in reverse order */
> + unsigned int icur = pcl->pclusterpages;
>
> - while (fe->icur > 0) {
> - if (!cmpxchg(&pcl->compressed_bvecs[--fe->icur].page,
> + while (icur > 0) {
> + if (!cmpxchg(&pcl->compressed_bvecs[--icur].page,
> NULL, bvec->page)) {
> - pcl->compressed_bvecs[fe->icur] = *bvec;
> + pcl->compressed_bvecs[icur] = *bvec;
> return true;
> }
> }
> @@ -877,8 +876,6 @@ static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
> }
> z_erofs_bvec_iter_begin(&fe->biter, &fe->pcl->bvset,
> Z_EROFS_INLINE_BVECS, fe->pcl->vcnt);
> - /* since file-backed online pages are traversed in reverse order */
> - fe->icur = z_erofs_pclusterpages(fe->pcl);
> return 0;
> }
>

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