[RFC PATCH 6/6] btrfs: zlib: add support for zlib-deflate through acomp

[Giovanni Cabiddu <giovanni.cabiddu@intel.com>]

From: Weigang Li <weigang.li@intel.com>

Add support for zlib compression and decompression through the acomp
APIs.
Input pages are added to an sg-list and sent to acomp in one request.
Since acomp is asynchronous, the thread is put to sleep and then the CPU
is freed up. Once compression is done, the acomp callback is triggered
and the thread is woke up.

This patch doesn't change the BTRFS disk format, this means that files
compressed by hardware engines can be de-compressed by the zlib software
library, and vice versa.

Limitations:
  * The implementation tries always to use an acomp even if only
    zlib-deflate-scomp is present
  * Acomp does not provide a way to support compression levels
  * Acomp is an asynchronous API but used here synchronously

Signed-off-by: Weigang Li <weigang.li@intel.com>
---
 fs/btrfs/zlib.c | 216 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 216 insertions(+)

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index e5b3f2003896..b5bbb8c97244 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -18,6 +18,8 @@
 #include <linux/pagemap.h>
 #include <linux/bio.h>
 #include <linux/refcount.h>
+#include <crypto/acompress.h>
+#include <linux/scatterlist.h>
 #include "compression.h"
 
 /* workspace buffer size for s390 zlib hardware support */
@@ -33,6 +35,201 @@ struct workspace {
 
 static struct workspace_manager wsm;
 
+static int acomp_comp_pages(struct address_space *mapping, u64 start,
+			    unsigned long len, struct page **pages,
+			    unsigned long *out_pages,
+			    unsigned long *total_in,
+			    unsigned long *total_out)
+{
+	unsigned int nr_src_pages = 0, nr_dst_pages = 0, nr_pages = 0;
+	struct sg_table in_sg = { 0 }, out_sg = { 0 };
+	struct page *in_page, *out_page, **in_pages;
+	struct crypto_acomp *tfm = NULL;
+	struct acomp_req *req = NULL;
+	struct crypto_wait wait;
+	int ret, i;
+
+	nr_src_pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	in_pages = kcalloc(nr_src_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!in_pages) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0; i < nr_src_pages; i++) {
+		in_page = find_get_page(mapping, start >> PAGE_SHIFT);
+		out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+		if (!in_page || !out_page) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		in_pages[i] = in_page;
+		pages[i] = out_page;
+		nr_dst_pages += 1;
+		start += PAGE_SIZE;
+	}
+
+	ret = sg_alloc_table_from_pages(&in_sg, in_pages, nr_src_pages, 0,
+					nr_src_pages << PAGE_SHIFT, GFP_KERNEL);
+	if (ret)
+		goto out;
+
+	ret = sg_alloc_table_from_pages(&out_sg, pages, nr_dst_pages, 0,
+					nr_dst_pages << PAGE_SHIFT, GFP_KERNEL);
+	if (ret)
+		goto out;
+
+	crypto_init_wait(&wait);
+	tfm = crypto_alloc_acomp("zlib-deflate", 0, 0);
+	if (IS_ERR(tfm)) {
+		ret = PTR_ERR(tfm);
+		goto out;
+	}
+
+	req = acomp_request_alloc(tfm);
+	if (!req) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	acomp_request_set_params(req, in_sg.sgl, out_sg.sgl, len,
+				 nr_dst_pages << PAGE_SHIFT);
+	acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				   crypto_req_done, &wait);
+
+	ret = crypto_wait_req(crypto_acomp_compress(req), &wait);
+	if (ret)
+		goto out;
+
+	*total_in = len;
+	*total_out = req->dlen;
+	nr_pages = (*total_out + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+out:
+	sg_free_table(&in_sg);
+	sg_free_table(&out_sg);
+
+	if (in_pages) {
+		for (i = 0; i < nr_src_pages; i++)
+			put_page(in_pages[i]);
+		kfree(in_pages);
+	}
+
+	/* free un-used out pages */
+	for (i = nr_pages; i < nr_dst_pages; i++)
+		put_page(pages[i]);
+
+	if (req)
+		acomp_request_free(req);
+
+	if (tfm)
+		crypto_free_acomp(tfm);
+
+	*out_pages = nr_pages;
+
+	return ret;
+}
+
+static int acomp_zlib_decomp_bio(struct page **in_pages,
+				 struct compressed_bio *cb, size_t srclen,
+				 unsigned long total_pages_in)
+{
+	unsigned int nr_dst_pages = BTRFS_MAX_COMPRESSED_PAGES;
+	struct sg_table in_sg = { 0 }, out_sg = { 0 };
+	struct bio *orig_bio = &cb->orig_bbio->bio;
+	char *data_out = NULL, *bv_buf = NULL;
+	int copy_len = 0, bytes_left = 0;
+	struct crypto_acomp *tfm = NULL;
+	struct page **out_pages = NULL;
+	struct acomp_req *req = NULL;
+	struct crypto_wait wait;
+	struct bio_vec bvec;
+	int ret, i = 0;
+
+	ret = sg_alloc_table_from_pages(&in_sg, in_pages, total_pages_in,
+					0, srclen, GFP_KERNEL);
+	if (ret)
+		goto out;
+
+	out_pages = kcalloc(nr_dst_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!out_pages) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0; i < nr_dst_pages; i++) {
+		out_pages[i] = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+		if (!out_pages[i]) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	ret = sg_alloc_table_from_pages(&out_sg, out_pages, nr_dst_pages, 0,
+					nr_dst_pages << PAGE_SHIFT, GFP_KERNEL);
+	if (ret)
+		goto out;
+
+	crypto_init_wait(&wait);
+	tfm = crypto_alloc_acomp("zlib-deflate", 0, 0);
+	if (IS_ERR(tfm)) {
+		ret = PTR_ERR(tfm);
+		goto out;
+	}
+
+	req = acomp_request_alloc(tfm);
+	if (!req) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	acomp_request_set_params(req, in_sg.sgl, out_sg.sgl, srclen,
+				 nr_dst_pages << PAGE_SHIFT);
+	acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				   crypto_req_done, &wait);
+
+	ret = crypto_wait_req(crypto_acomp_decompress(req), &wait);
+	if (ret)
+		goto out;
+
+	/* Copy decompressed buffer to bio pages */
+	bytes_left = req->dlen;
+	for (i = 0; i < nr_dst_pages; i++) {
+		copy_len = bytes_left > PAGE_SIZE ? PAGE_SIZE : bytes_left;
+		data_out = kmap_local_page(out_pages[i]);
+
+		bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
+		bv_buf = kmap_local_page(bvec.bv_page);
+		memcpy(bv_buf, data_out, copy_len);
+		kunmap_local(bv_buf);
+
+		bio_advance(orig_bio, copy_len);
+		if (!orig_bio->bi_iter.bi_size)
+			break;
+		bytes_left -= copy_len;
+		if (bytes_left <= 0)
+			break;
+	}
+out:
+	sg_free_table(&in_sg);
+	sg_free_table(&out_sg);
+
+	if (out_pages) {
+		for (i = 0; i < nr_dst_pages; i++) {
+			if (out_pages[i])
+				put_page(out_pages[i]);
+		}
+		kfree(out_pages);
+	}
+
+	if (req)
+		acomp_request_free(req);
+	if (tfm)
+		crypto_free_acomp(tfm);
+
+	return ret;
+}
+
 struct list_head *zlib_get_workspace(unsigned int level)
 {
 	struct list_head *ws = btrfs_get_workspace(BTRFS_COMPRESS_ZLIB, level);
@@ -108,6 +305,15 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
 	unsigned long nr_dest_pages = *out_pages;
 	const unsigned long max_out = nr_dest_pages * PAGE_SIZE;
 
+	if (crypto_has_acomp("zlib-deflate", 0, 0)) {
+		ret = acomp_comp_pages(mapping, start, len, pages, out_pages,
+				       total_in, total_out);
+		if (!ret)
+			return ret;
+
+		pr_warn("BTRFS: acomp compression failed: ret = %d\n", ret);
+		/* Fallback to SW implementation if HW compression failed */
+	}
 	*out_pages = 0;
 	*total_out = 0;
 	*total_in = 0;
@@ -281,6 +487,16 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long buf_start;
 	struct page **pages_in = cb->compressed_pages;
 
+	if (crypto_has_acomp("zlib-deflate", 0, 0)) {
+		ret = acomp_zlib_decomp_bio(pages_in, cb, srclen,
+					    total_pages_in);
+		if (!ret)
+			return ret;
+
+		pr_warn("BTRFS: acomp decompression failed, ret=%d\n", ret);
+		/* Fallback to SW implementation if HW decompression failed */
+	}
+
 	data_in = kmap_local_page(pages_in[page_in_index]);
 	workspace->strm.next_in = data_in;
 	workspace->strm.avail_in = min_t(size_t, srclen, PAGE_SIZE);
-- 
2.44.0