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Subject[RFC PATCH v2 1/2] erofs: support interlaced uncompressed data for compressed files
Date
From: Yue Hu <huyue2@coolpad.com>

Currently, there is no start offset when writing uncompressed data to
disk blocks for compressed files. However, we are using in-place I/O
which will decrease the number of memory copies a lot if we write it
just from an offset of 'pageofs_out'. So, let's support it.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
---
fs/erofs/compress.h | 3 +++
fs/erofs/decompressor.c | 12 +++++++-----
fs/erofs/erofs_fs.h | 2 ++
fs/erofs/zdata.c | 11 ++++++++++-
fs/erofs/zdata.h | 3 +++
5 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
index 26fa170090b8..cef26c63d6b1 100644
--- a/fs/erofs/compress.h
+++ b/fs/erofs/compress.h
@@ -15,6 +15,9 @@ struct z_erofs_decompress_req {
unsigned short pageofs_in, pageofs_out;
unsigned int inputsize, outputsize;

+ /* cut point of interlaced uncompressed data */
+ unsigned int interlaced_offset;
+
/* indicate the algorithm will be used for decompression */
unsigned int alg;
bool inplace_io, partial_decoding, fillgaps;
diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 2d55569f96ac..e5dc8eb992b1 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -340,18 +340,20 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
src = kmap_atomic(*rq->in) + rq->pageofs_in;
if (rq->out[0]) {
dst = kmap_atomic(rq->out[0]);
- memcpy(dst + rq->pageofs_out, src, righthalf);
+ memcpy(dst + rq->pageofs_out, src + rq->interlaced_offset,
+ righthalf);
kunmap_atomic(dst);
}

if (nrpages_out == 2) {
DBG_BUGON(!rq->out[1]);
- if (rq->out[1] == *rq->in) {
- memmove(src, src + righthalf, lefthalf);
- } else {
+ if (rq->out[1] != *rq->in) {
dst = kmap_atomic(rq->out[1]);
- memcpy(dst, src + righthalf, lefthalf);
+ memcpy(dst, rq->interlaced_offset ? src :
+ (src + righthalf), lefthalf);
kunmap_atomic(dst);
+ } else if (!rq->interlaced_offset) {
+ memmove(src, src + righthalf, lefthalf);
}
}
kunmap_atomic(src);
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/zdata.c b/fs/erofs/zdata.c
index 5792ca9e0d5e..4863d9d960d5 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -481,6 +481,7 @@ static void z_erofs_try_to_claim_pcluster(struct z_erofs_decompress_frontend *f)

static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
{
+ struct erofs_inode *const vi = EROFS_I(fe->inode);
struct erofs_map_blocks *map = &fe->map;
bool ztailpacking = map->m_flags & EROFS_MAP_META;
struct z_erofs_pcluster *pcl;
@@ -508,6 +509,11 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
pcl->pageofs_out = map->m_la & ~PAGE_MASK;
fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;

+ pcl->interlaced = false;
+ if ((vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER) &&
+ pcl->algorithmformat == Z_EROFS_COMPRESSION_SHIFTED)
+ pcl->interlaced = true;
+
/*
* lock all primary followed works before visible to others
* and mutex_trylock *never* fails for a new pcluster.
@@ -972,7 +978,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
struct z_erofs_pcluster *pcl = be->pcl;
unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
- unsigned int i, inputsize;
+ unsigned int i, inputsize, interlaced_offset;
int err2;
struct page *page;
bool overlapped;
@@ -1015,6 +1021,8 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
else
inputsize = pclusterpages * PAGE_SIZE;

+ interlaced_offset = pcl->interlaced ? pcl->pageofs_out : 0;
+
err = z_erofs_decompress(&(struct z_erofs_decompress_req) {
.sb = be->sb,
.in = be->compressed_pages,
@@ -1023,6 +1031,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
.pageofs_out = pcl->pageofs_out,
.inputsize = inputsize,
.outputsize = pcl->length,
+ .interlaced_offset = interlaced_offset,
.alg = pcl->algorithmformat,
.inplace_io = overlapped,
.partial_decoding = pcl->partial,
diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
index e7f04c4fbb81..75f3a52fc66f 100644
--- a/fs/erofs/zdata.h
+++ b/fs/erofs/zdata.h
@@ -87,6 +87,9 @@ struct z_erofs_pcluster {
/* L: indicate several pageofs_outs or not */
bool multibases;

+ /* I: whether interlaced uncompressed data or not */
+ bool interlaced;
+
/* A: compressed bvecs (can be cached or inplaced pages) */
struct z_erofs_bvec compressed_bvecs[];
};
--
2.17.1
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