diff options
| author | Gao Xiang <gaoxiang25@huawei.com> | 2019-06-24 15:22:56 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-26 09:44:40 +0800 |
| commit | 0ffd71bcc3a03ebb3551661a36052488369c4de9 (patch) | |
| tree | 8c75db866178919fcac405c5415ff4b505af793a | |
| parent | 7fc45dbc938a2e69ecd6a78a3c0074aa6c11fac9 (diff) | |
staging: erofs: introduce LZ4 decompression inplace
compressed data will be usually loaded into last pages of
the extent (the last page for 4k) for in-place decompression
(more specifically, in-place IO), as ilustration below,
start of compressed logical extent
| end of this logical extent
| |
______v___________________________v________
... | page 6 | page 7 | page 8 | page 9 | ...
|__________|__________|__________|__________|
. ^ . ^
. |compressed|
. | data |
. . .
|< dstsize >|<margin>|
oend iend
op ip
Therefore, it's possible to do decompression inplace (thus no
memcpy at all) if the margin is sufficient and safe enough [1],
and it can be implemented only for fixed-size output compression
compared with fixed-size input compression.
No memcpy for most of in-place IO (about 99% of enwik9) after
decompression inplace is implemented and sequential read will
be improved of course (see the following patches for test results).
[1] https://github.com/lz4/lz4/commit/b17f578a919b7e6b078cede2d52be29dd48c8e8c
https://github.com/lz4/lz4/commit/5997e139f53169fa3a1c1b4418d2452a90b01602
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/staging/erofs/compress.h | 1 | ||||
| -rw-r--r-- | drivers/staging/erofs/decompressor.c | 36 | ||||
| -rw-r--r-- | drivers/staging/erofs/erofs_fs.h | 3 |
3 files changed, 35 insertions, 5 deletions
diff --git a/drivers/staging/erofs/compress.h b/drivers/staging/erofs/compress.h index ebeccb1f4eae..c43aa3374d28 100644 --- a/drivers/staging/erofs/compress.h +++ b/drivers/staging/erofs/compress.h @@ -17,6 +17,7 @@ enum { }; struct z_erofs_decompress_req { + struct super_block *sb; struct page **in, **out; unsigned short pageofs_out; diff --git a/drivers/staging/erofs/decompressor.c b/drivers/staging/erofs/decompressor.c index df8fd68a338b..80f1f39719ba 100644 --- a/drivers/staging/erofs/decompressor.c +++ b/drivers/staging/erofs/decompressor.c @@ -14,6 +14,9 @@ #endif #define LZ4_MAX_DISTANCE_PAGES DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) +#ifndef LZ4_DECOMPRESS_INPLACE_MARGIN +#define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize) (((srcsize) >> 8) + 32) +#endif struct z_erofs_decompressor { /* @@ -112,7 +115,7 @@ static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out) { unsigned int inputmargin, inlen; u8 *src; - bool copied; + bool copied, support_0padding; int ret; if (rq->inputsize > PAGE_SIZE) @@ -120,13 +123,38 @@ static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out) src = kmap_atomic(*rq->in); inputmargin = 0; + support_0padding = false; + + /* decompression inplace is only safe when 0padding is enabled */ + if (EROFS_SB(rq->sb)->requirements & EROFS_REQUIREMENT_LZ4_0PADDING) { + support_0padding = true; + + while (!src[inputmargin & ~PAGE_MASK]) + if (!(++inputmargin & ~PAGE_MASK)) + break; + + if (inputmargin >= rq->inputsize) { + kunmap_atomic(src); + return -EIO; + } + } copied = false; inlen = rq->inputsize - inputmargin; if (rq->inplace_io) { - src = generic_copy_inplace_data(rq, src, inputmargin); - inputmargin = 0; - copied = true; + const uint oend = (rq->pageofs_out + + rq->outputsize) & ~PAGE_MASK; + const uint nr = PAGE_ALIGN(rq->pageofs_out + + rq->outputsize) >> PAGE_SHIFT; + + if (rq->partial_decoding || !support_0padding || + rq->out[nr - 1] != rq->in[0] || + rq->inputsize - oend < + LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) { + src = generic_copy_inplace_data(rq, src, inputmargin); + inputmargin = 0; + copied = true; + } } ret = LZ4_decompress_safe_partial(src + inputmargin, out, diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h index 9a9aaf2d9fbb..9f61abb7c1ca 100644 --- a/drivers/staging/erofs/erofs_fs.h +++ b/drivers/staging/erofs/erofs_fs.h @@ -21,7 +21,8 @@ * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be * incompatible with this kernel version. */ -#define EROFS_ALL_REQUIREMENTS 0 +#define EROFS_REQUIREMENT_LZ4_0PADDING 0x00000001 +#define EROFS_ALL_REQUIREMENTS EROFS_REQUIREMENT_LZ4_0PADDING struct erofs_super_block { /* 0 */__le32 magic; /* in the little endian */ |