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erofs: refine z_erofs_transform_plain() for sub-page block support 

Sub-page block support is still unusable even with previous commits if
interlaced PLAIN pclusters exist.  Such pclusters can be found if the
fragment feature is enabled.

This commit tries to handle "the head part" of interlaced PLAIN
pclusters first: it was once explained in commit fdffc091e6 ("erofs:
support interlaced uncompressed data for compressed files").

It uses a unique way for both shifted and interlaced PLAIN pclusters.
As an added bonus, PLAIN pclusters larger than the block size is also
supported now for the upcoming large lclusters.

Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231206091057.87027-5-hsiangkao@linux.alibaba.com
This commit is contained in:
Gao Xiang 2023-12-06 17:10:56 +08:00
parent e5aba911de
commit 1ca0152014
1 changed files with 48 additions and 33 deletions
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81
fs/erofs/decompressor.c
View File

@ -320,43 +320,58 @@ dstmap_out:
static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
struct page **pagepool)
{
const unsigned int inpages = PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
const unsigned int outpages =
const unsigned int nrpages_in =
PAGE_ALIGN(rq->pageofs_in + rq->inputsize) >> PAGE_SHIFT;
const unsigned int nrpages_out =
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;
u8 *src;
const unsigned int bs = rq->sb->s_blocksize;
unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
u8 *kin;
if (outpages > 2 && rq->alg == Z_EROFS_COMPRESSION_SHIFTED) {
DBG_BUGON(1);
return -EFSCORRUPTED;
}
if (rq->out[0] == *rq->in) {
DBG_BUGON(rq->pageofs_out);
return 0;
}
src = kmap_local_page(rq->in[inpages - 1]) + rq->pageofs_in;
if (rq->out[0])
memcpy_to_page(rq->out[0], rq->pageofs_out,
src + interlaced_offset, righthalf);
if (outpages > inpages) {
DBG_BUGON(!rq->out[outpages - 1]);
if (rq->out[outpages - 1] != rq->in[inpages - 1]) {
memcpy_to_page(rq->out[outpages - 1], 0, src +
(interlaced_offset ? 0 : righthalf),
lefthalf);
} else if (!interlaced_offset) {
memmove(src, src + righthalf, lefthalf);
flush_dcache_page(rq->in[inpages - 1]);
DBG_BUGON(rq->outputsize > rq->inputsize);
if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
cur = bs - (rq->pageofs_out & (bs - 1));
pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
cur = min(cur, rq->outputsize);
if (cur && rq->out[0]) {
kin = kmap_local_page(rq->in[nrpages_in - 1]);
if (rq->out[0] == rq->in[nrpages_in - 1]) {
memmove(kin + rq->pageofs_out, kin + pi, cur);
flush_dcache_page(rq->out[0]);
} else {
memcpy_to_page(rq->out[0], rq->pageofs_out,
kin + pi, cur);
}
kunmap_local(kin);
}
rq->outputsize -= cur;
}
kunmap_local(src);
for (; rq->outputsize; rq->pageofs_in = 0, cur += PAGE_SIZE, ni++) {
insz = min(PAGE_SIZE - rq->pageofs_in, rq->outputsize);
rq->outputsize -= insz;
if (!rq->in[ni])
continue;
kin = kmap_local_page(rq->in[ni]);
pi = 0;
do {
no = (rq->pageofs_out + cur + pi) >> PAGE_SHIFT;
po = (rq->pageofs_out + cur + pi) & ~PAGE_MASK;
DBG_BUGON(no >= nrpages_out);
cnt = min(insz - pi, PAGE_SIZE - po);
if (rq->out[no] == rq->in[ni]) {
memmove(kin + po,
kin + rq->pageofs_in + pi, cnt);
flush_dcache_page(rq->out[no]);
} else if (rq->out[no]) {
memcpy_to_page(rq->out[no], po,
kin + rq->pageofs_in + pi, cnt);
}
pi += cnt;
} while (pi < insz);
kunmap_local(kin);
}
DBG_BUGON(ni > nrpages_in);
return 0;
}