[PATCH] erofs-utils: mkfs: skip the redundant write for ztailpacking block

[Noboru Asai]

In this patch, the value of blkaddr in z_erofs_lcluster_index
corresponding to the ztailpacking block in the extent list
is invalid value. It looks that the linux kernel doesn't refer to this
value, but what value is correct?
0 or -1 (EROFS_NULL_ADDR) or don't care?

2024年4月17日(水) 23:43 Yifan Zhao <zhaoyifan at sjtu.edu.cn>:
>
> z_erofs_merge_segment() doesn't consider the ztailpacking block in the
> extent list and unnecessarily writes it back to the disk. This patch
> fixes this issue by introducing a new `inlined` field in the struct
> `z_erofs_inmem_extent`.
>
> Signed-off-by: Yifan Zhao <zhaoyifan at sjtu.edu.cn>
> ---
>  include/erofs/dedupe.h | 2 +-
>  lib/compress.c         | 8 ++++++++
>  lib/dedupe.c           | 1 +
>  3 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/include/erofs/dedupe.h b/include/erofs/dedupe.h
> index 153bd4c..4cbfb2c 100644
> --- a/include/erofs/dedupe.h
> +++ b/include/erofs/dedupe.h
> @@ -16,7 +16,7 @@ struct z_erofs_inmem_extent {
>         erofs_blk_t blkaddr;
>         unsigned int compressedblks;
>         unsigned int length;
> -       bool raw, partial;
> +       bool raw, partial, inlined;
>  };
>
>  struct z_erofs_dedupe_ctx {
> diff --git a/lib/compress.c b/lib/compress.c
> index 74c5707..41628e7 100644
> --- a/lib/compress.c
> +++ b/lib/compress.c
> @@ -572,6 +572,7 @@ nocompression:
>                  */
>                 e->compressedblks = 1;
>                 e->raw = true;
> +               e->inlined = false;
>         } else if (may_packing && len == e->length &&
>                    compressedsize < ctx->pclustersize &&
>                    (!inode->fragment_size || ictx->fix_dedupedfrag)) {
> @@ -582,6 +583,7 @@ frag_packing:
>                         return ret;
>                 e->compressedblks = 0; /* indicate a fragment */
>                 e->raw = false;
> +               e->inlined = false;
>                 ictx->fragemitted = true;
>         /* tailpcluster should be less than 1 block */
>         } else if (may_inline && len == e->length && compressedsize < blksz) {
> @@ -600,6 +602,7 @@ frag_packing:
>                         return ret;
>                 e->compressedblks = 1;
>                 e->raw = false;
> +               e->inlined = true;
>         } else {
>                 unsigned int tailused, padding;
>
> @@ -652,6 +655,7 @@ frag_packing:
>                                 return ret;
>                 }
>                 e->raw = false;
> +               e->inlined = false;
>                 may_inline = false;
>                 may_packing = false;
>         }
> @@ -1151,6 +1155,9 @@ int z_erofs_merge_segment(struct z_erofs_compress_ictx *ictx,
>                 ei->e.blkaddr = sctx->blkaddr;
>                 sctx->blkaddr += ei->e.compressedblks;
>
> +               if (ei->e.inlined)
> +                       continue;
> +
>                 ret2 = blk_write(sbi, sctx->membuf + blkoff * erofs_blksiz(sbi),
>                                  ei->e.blkaddr, ei->e.compressedblks);
>                 blkoff += ei->e.compressedblks;
> @@ -1374,6 +1381,7 @@ int erofs_write_compressed_file(struct erofs_inode *inode, int fd, u64 fpos)
>                         .compressedblks = 0,
>                         .raw = false,
>                         .partial = false,
> +                       .inlined = false,
>                         .blkaddr = sctx.blkaddr,
>                 };
>                 init_list_head(&ei->list);
> diff --git a/lib/dedupe.c b/lib/dedupe.c
> index 19a1c8d..aaaccb5 100644
> --- a/lib/dedupe.c
> +++ b/lib/dedupe.c
> @@ -138,6 +138,7 @@ int z_erofs_dedupe_match(struct z_erofs_dedupe_ctx *ctx)
>                 ctx->e.partial = e->partial ||
>                         (window_size + extra < e->original_length);
>                 ctx->e.raw = e->raw;
> +               ctx->e.inlined = false;
>                 ctx->e.blkaddr = e->compressed_blkaddr;
>                 ctx->e.compressedblks = e->compressed_blks;
>                 return 0;
> --
> 2.44.0
>