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authorGao Xiang <gaoxiang25@huawei.com>2019-06-24 15:22:56 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-26 09:44:40 +0800
commit0ffd71bcc3a03ebb3551661a36052488369c4de9 (patch)
tree8c75db866178919fcac405c5415ff4b505af793a
parent7fc45dbc938a2e69ecd6a78a3c0074aa6c11fac9 (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.h1
-rw-r--r--drivers/staging/erofs/decompressor.c36
-rw-r--r--drivers/staging/erofs/erofs_fs.h3
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 */