erofs: introduce z_erofs_fixup_insize

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.

Link: https://lore.kernel.org/r/20211228054604.114518-3-hsiangkao@linux.alibaba.com
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
index 5794065..19e6c56 100644 (file)
--- 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 ebb478a..9281491 100644 (file)
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -184,6 +184,24 @@ docopy:
        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 5004551..05a3063 100644 (file)
--- 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 @@ again:
        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;