erofs: remove the fast path of per-CPU buffer decompression

As Xiang mentioned, such path has no real impact to our current
decompression strategy, remove it directly. Also, update the return
value of z_erofs_lz4_decompress() to 0 if success to keep consistent
with LZMA which will return 0 as well for that case.

Link: https://lore.kernel.org/r/20211014065744.1787-1-zbestahu@gmail.com
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Yue Hu <huyue2@yulong.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index a5bc4b1b7813e9a2b82e119074ef81336c004adf..dce06ac61893350fbbd0ccfb479d86742b4b1628 100644 (file)
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -242,6 +242,8 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
                if (ret >= 0)
                        memset(out + ret, 0, rq->outputsize - ret);
                ret = -EIO;
+       } else {
+               ret = 0;
        }
 
        if (maptype == 0) {
@@ -268,33 +270,6 @@ static struct z_erofs_decompressor decompressors[] = {
        },
 };
 
-static void copy_from_pcpubuf(struct page **out, const char *dst,
-                             unsigned short pageofs_out,
-                             unsigned int outputsize)
-{
-       const char *end = dst + outputsize;
-       const unsigned int righthalf = PAGE_SIZE - pageofs_out;
-       const char *cur = dst - pageofs_out;
-
-       while (cur < end) {
-               struct page *const page = *out++;
-
-               if (page) {
-                       char *buf = kmap_atomic(page);
-
-                       if (cur >= dst) {
-                               memcpy(buf, cur, min_t(uint, PAGE_SIZE,
-                                                      end - cur));
-                       } else {
-                               memcpy(buf + pageofs_out, cur + pageofs_out,
-                                      min_t(uint, righthalf, end - cur));
-                       }
-                       kunmap_atomic(buf);
-               }
-               cur += PAGE_SIZE;
-       }
-}
-
 static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
                                      struct list_head *pagepool)
 {
@@ -305,34 +280,12 @@ static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
        void *dst;
        int ret;
 
-       /* two optimized fast paths only for non bigpcluster cases yet */
-       if (rq->inputsize <= PAGE_SIZE) {
-               if (nrpages_out == 1 && !rq->inplace_io) {
-                       DBG_BUGON(!*rq->out);
-                       dst = kmap_atomic(*rq->out);
-                       dst_maptype = 0;
-                       goto dstmap_out;
-               }
-
-               /*
-                * For the case of small output size (especially much less
-                * than PAGE_SIZE), memcpy the decompressed data rather than
-                * compressed data is preferred.
-                */
-               if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
-                       dst = erofs_get_pcpubuf(1);
-                       if (IS_ERR(dst))
-                               return PTR_ERR(dst);
-
-                       rq->inplace_io = false;
-                       ret = alg->decompress(rq, dst);
-                       if (!ret)
-                               copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
-                                                 rq->outputsize);
-
-                       erofs_put_pcpubuf(dst);
-                       return ret;
-               }
+       /* one optimized fast path only for non bigpcluster cases yet */
+       if (rq->inputsize <= PAGE_SIZE && nrpages_out == 1 && !rq->inplace_io) {
+               DBG_BUGON(!*rq->out);
+               dst = kmap_atomic(*rq->out);
+               dst_maptype = 0;
+               goto dstmap_out;
        }
 
        /* general decoding path which can be used for all cases */