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Message-ID: <YyQ8JK812r/tiDW0@B-P7TQMD6M-0146.local>
Date: Fri, 16 Sep 2022 17:04:36 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Yue Hu <zbestahu@...il.com>
Cc: xiang@...nel.org, chao@...nel.org, linux-erofs@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, zhangwen@...lpad.com,
shaojunjun@...lpad.com, Yue Hu <huyue2@...lpad.com>
Subject: Re: [RFC PATCH v4 1/2] erofs: support interlaced uncompressed data
for compressed files
On Tue, Sep 13, 2022 at 07:05:51PM +0800, Yue Hu wrote:
> From: Yue Hu <huyue2@...lpad.com>
>
> Currently, uncompressed data is all handled in the shifted way, which
> means we have to shift the whole on-disk plain pcluster to get the
> logical data. However, since we are also using in-place I/O for
> uncompressed data, data copy will be reduced a lot if pcluster is
> recorded in the interlaced way as illustrated below:
> _______________________________________________________________
> | | | |_ tail part |_ head part _|
> |<- blk0 ->| .. |<- blkn-2 ->|<- blkn-1 ->|
>
> The logical data then becomes:
> ________________________________________________________
> |_ head part _|_ blk0 _| .. |_ blkn-2 _|_ tail part _|
>
> In addition, non-4k plain pclusters are also survived by the
> interlaced way, which can be used for non-4k lclusters as well.
>
> However, it's almost impossible to de-duplicate uncompressed data
> in the interlaced way, therefore shifted uncompressed data is still
> useful.
>
> Signed-off-by: Yue Hu <huyue2@...lpad.com>
This version looks good to me,
Reviewed-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
Thanks,
Gao Xiang
> fs/erofs/decompressor.c | 47 ++++++++++++++++++++++++-----------------
> fs/erofs/erofs_fs.h | 2 ++
> fs/erofs/internal.h | 1 +
> fs/erofs/zmap.c | 14 ++++++++----
> 4 files changed, 41 insertions(+), 23 deletions(-)
>
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index 2d55569f96ac..51b7ac7166d9 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -317,52 +317,61 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq,
> return ret;
> }
>
> -static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
> - struct page **pagepool)
> +static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
> + struct page **pagepool)
> {
> - const unsigned int nrpages_out =
> + const unsigned int inpages = PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
> + const unsigned int outpages =
> PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
> const unsigned int righthalf = min_t(unsigned int, rq->outputsize,
> PAGE_SIZE - rq->pageofs_out);
> const unsigned int lefthalf = rq->outputsize - righthalf;
> + const unsigned int interlaced_offset =
> + rq->alg == Z_EROFS_COMPRESSION_SHIFTED ? 0 : rq->pageofs_out;
> unsigned char *src, *dst;
>
> - if (nrpages_out > 2) {
> + if (outpages > 2 && rq->alg == Z_EROFS_COMPRESSION_SHIFTED) {
> DBG_BUGON(1);
> - return -EIO;
> + return -EFSCORRUPTED;
> }
>
> if (rq->out[0] == *rq->in) {
> - DBG_BUGON(nrpages_out != 1);
> + DBG_BUGON(rq->pageofs_out);
> return 0;
> }
>
> - src = kmap_atomic(*rq->in) + rq->pageofs_in;
> + src = kmap_local_page(rq->in[inpages - 1]) + rq->pageofs_in;
> if (rq->out[0]) {
> - dst = kmap_atomic(rq->out[0]);
> - memcpy(dst + rq->pageofs_out, src, righthalf);
> - kunmap_atomic(dst);
> + dst = kmap_local_page(rq->out[0]);
> + memcpy(dst + rq->pageofs_out, src + interlaced_offset,
> + righthalf);
> + kunmap_local(dst);
> }
>
> - if (nrpages_out == 2) {
> - DBG_BUGON(!rq->out[1]);
> - if (rq->out[1] == *rq->in) {
> + if (outpages > inpages) {
> + DBG_BUGON(!rq->out[outpages - 1]);
> + if (rq->out[outpages - 1] != rq->in[inpages - 1]) {
> + dst = kmap_local_page(rq->out[outpages - 1]);
> + memcpy(dst, interlaced_offset ? src :
> + (src + righthalf), lefthalf);
> + kunmap_local(dst);
> + } else if (!interlaced_offset) {
> memmove(src, src + righthalf, lefthalf);
> - } else {
> - dst = kmap_atomic(rq->out[1]);
> - memcpy(dst, src + righthalf, lefthalf);
> - kunmap_atomic(dst);
> }
> }
> - kunmap_atomic(src);
> + kunmap_local(src);
> return 0;
> }
>
> static struct z_erofs_decompressor decompressors[] = {
> [Z_EROFS_COMPRESSION_SHIFTED] = {
> - .decompress = z_erofs_shifted_transform,
> + .decompress = z_erofs_transform_plain,
> .name = "shifted"
> },
> + [Z_EROFS_COMPRESSION_INTERLACED] = {
> + .decompress = z_erofs_transform_plain,
> + .name = "interlaced"
> + },
> [Z_EROFS_COMPRESSION_LZ4] = {
> .decompress = z_erofs_lz4_decompress,
> .name = "lz4"
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 2b48373f690b..5c1de6d7ad71 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -295,11 +295,13 @@ struct z_erofs_lzma_cfgs {
> * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
> * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
> * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
> + * bit 4 : interlaced plain pcluster (0 - off; 1 - on)
> */
> #define Z_EROFS_ADVISE_COMPACTED_2B 0x0001
> #define Z_EROFS_ADVISE_BIG_PCLUSTER_1 0x0002
> #define Z_EROFS_ADVISE_BIG_PCLUSTER_2 0x0004
> #define Z_EROFS_ADVISE_INLINE_PCLUSTER 0x0008
> +#define Z_EROFS_ADVISE_INTERLACED_PCLUSTER 0x0010
>
> struct z_erofs_map_header {
> __le16 h_reserved1;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index cfee49d33b95..f3ed36445d73 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -436,6 +436,7 @@ struct erofs_map_blocks {
>
> enum {
> Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
> + Z_EROFS_COMPRESSION_INTERLACED,
> Z_EROFS_COMPRESSION_RUNTIME_MAX
> };
>
> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> index d58549ca1df9..7196235a441c 100644
> --- a/fs/erofs/zmap.c
> +++ b/fs/erofs/zmap.c
> @@ -679,12 +679,18 @@ static int z_erofs_do_map_blocks(struct inode *inode,
> goto out;
> }
>
> - if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN)
> - map->m_algorithmformat = Z_EROFS_COMPRESSION_SHIFTED;
> - else if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2)
> + if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN) {
> + if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
> + map->m_algorithmformat =
> + Z_EROFS_COMPRESSION_INTERLACED;
> + else
> + map->m_algorithmformat =
> + Z_EROFS_COMPRESSION_SHIFTED;
> + } else if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) {
> map->m_algorithmformat = vi->z_algorithmtype[1];
> - else
> + } else {
> map->m_algorithmformat = vi->z_algorithmtype[0];
> + }
>
> if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
> ((flags & EROFS_GET_BLOCKS_READMORE) &&
> --
> 2.17.1
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