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Subject[PATCH v4 2/5] erofs: introduce z_erofs_fixup_insize
Date
To prepare for the upcoming ztailpacking feature, introduce
z_erofs_fixup_insize() and pageofs_in to wrap up the process
to get the exact compressed size via zero padding.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
fs/erofs/compress.h | 4 +++-
fs/erofs/decompressor.c | 34 +++++++++++++++++++++++++---------
fs/erofs/decompressor_lzma.c | 19 ++++++++-----------
3 files changed, 36 insertions(+), 21 deletions(-)

diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
index 579406504919..19e6c56a9f47 100644
--- a/fs/erofs/compress.h
+++ b/fs/erofs/compress.h
@@ -12,7 +12,7 @@ struct z_erofs_decompress_req {
struct super_block *sb;
struct page **in, **out;

- unsigned short pageofs_out;
+ unsigned short pageofs_in, pageofs_out;
unsigned int inputsize, outputsize;

/* indicate the algorithm will be used for decompression */
@@ -87,6 +87,8 @@ static inline bool erofs_page_is_managed(const struct erofs_sb_info *sbi,
return page->mapping == MNGD_MAPPING(sbi);
}

+int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
+ unsigned int padbufsize);
int z_erofs_decompress(struct z_erofs_decompress_req *rq,
struct page **pagepool);

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 1d137fd42306..b8b2a3e34053 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -184,6 +184,24 @@ static void *z_erofs_lz4_handle_overlap(struct z_erofs_lz4_decompress_ctx *ctx,
return src;
}

+/*
+ * Get the exact inputsize with zero_padding feature.
+ * - For LZ4, it should work if zero_padding feature is on (5.3+);
+ * - For MicroLZMA, it'd be enabled all the time.
+ */
+int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
+ unsigned int padbufsize)
+{
+ const char *padend;
+
+ padend = memchr_inv(padbuf, 0, padbufsize);
+ if (!padend)
+ return -EFSCORRUPTED;
+ rq->inputsize -= padend - padbuf;
+ rq->pageofs_in += padend - padbuf;
+ return 0;
+}
+
static int z_erofs_lz4_decompress_mem(struct z_erofs_lz4_decompress_ctx *ctx,
u8 *out)
{
@@ -198,21 +216,19 @@ static int z_erofs_lz4_decompress_mem(struct z_erofs_lz4_decompress_ctx *ctx,
inputmargin = 0;
support_0padding = false;

- /* decompression inplace is only safe when zero_padding is enabled */
+ /* LZ4 decompression inplace is only safe if zero_padding is enabled */
if (erofs_sb_has_zero_padding(EROFS_SB(rq->sb))) {
support_0padding = true;
-
- while (!headpage[inputmargin & ~PAGE_MASK])
- if (!(++inputmargin & ~PAGE_MASK))
- break;
-
- if (inputmargin >= rq->inputsize) {
+ ret = z_erofs_fixup_insize(rq, headpage + rq->pageofs_in,
+ min_t(unsigned int, rq->inputsize,
+ EROFS_BLKSIZ - rq->pageofs_in));
+ if (ret) {
kunmap_atomic(headpage);
- return -EIO;
+ return ret;
}
}

- rq->inputsize -= inputmargin;
+ inputmargin = rq->pageofs_in;
src = z_erofs_lz4_handle_overlap(ctx, headpage, &inputmargin,
&maptype, support_0padding);
if (IS_ERR(src))
diff --git a/fs/erofs/decompressor_lzma.c b/fs/erofs/decompressor_lzma.c
index 50045510a1f4..05a3063cf2bc 100644
--- a/fs/erofs/decompressor_lzma.c
+++ b/fs/erofs/decompressor_lzma.c
@@ -156,7 +156,7 @@ int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
const unsigned int nrpages_in =
PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
- unsigned int inputmargin, inlen, outlen, pageofs;
+ unsigned int inlen, outlen, pageofs;
struct z_erofs_lzma *strm;
u8 *kin;
bool bounced = false;
@@ -164,16 +164,13 @@ int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,

/* 1. get the exact LZMA compressed size */
kin = kmap(*rq->in);
- inputmargin = 0;
- while (!kin[inputmargin & ~PAGE_MASK])
- if (!(++inputmargin & ~PAGE_MASK))
- break;
-
- if (inputmargin >= PAGE_SIZE) {
+ err = z_erofs_fixup_insize(rq, kin + rq->pageofs_in,
+ min_t(unsigned int, rq->inputsize,
+ EROFS_BLKSIZ - rq->pageofs_in));
+ if (err) {
kunmap(*rq->in);
- return -EFSCORRUPTED;
+ return err;
}
- rq->inputsize -= inputmargin;

/* 2. get an available lzma context */
again:
@@ -193,9 +190,9 @@ int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
xz_dec_microlzma_reset(strm->state, inlen, outlen,
!rq->partial_decoding);
pageofs = rq->pageofs_out;
- strm->buf.in = kin + inputmargin;
+ strm->buf.in = kin + rq->pageofs_in;
strm->buf.in_pos = 0;
- strm->buf.in_size = min_t(u32, inlen, PAGE_SIZE - inputmargin);
+ strm->buf.in_size = min_t(u32, inlen, PAGE_SIZE - rq->pageofs_in);
inlen -= strm->buf.in_size;
strm->buf.out = NULL;
strm->buf.out_pos = 0;
--
2.24.4
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