Commit 5b6e7e12 authored by Yue Hu's avatar Yue Hu Committed by Gao Xiang
Browse files

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: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: default avatarYue Hu <huyue2@yulong.com>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
parent 9e1ff307

fs/erofs/decompressor.c

+8 −55
Original line number Diff line number Diff line
@@ -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)

{
@@ -305,36 +280,14 @@ 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) {

	/* 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;

	}



		/*

		 * 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;

		}

	}



	/* general decoding path which can be used for all cases */

	ret = alg->prepare_destpages(rq, pagepool);

	if (ret < 0)