[Devel] [PATCH vz9 v2] dm-qcow2: support mixed compression images

[Alexander Atanasov]

Currently code uses only top qcow2 delta to handle decompression.
Images have compression type in the qcow2 header already set when  loaded.
To support mixed compression switch to use qio->qcow2 and respective
qcow2 header so the decompression is performed with the correct type.
Remove qcow2 argument in functions called from decompression where
possible and use qio->qcow2 which is the respective qcow2 image for
the qio, a qio references only one image.

https://virtuozzo.atlassian.net/browse/VSTOR-97155
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/md/dm-qcow2-map.c | 70 +++++++++++++++++++++++----------------
 1 file changed, 42 insertions(+), 28 deletions(-)


v1->v2:
 - drop extra stream reset for zstd 

diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
index ccc8d4484049..568bf68981b4 100644
--- a/drivers/md/dm-qcow2-map.c
+++ b/drivers/md/dm-qcow2-map.c
@@ -3009,8 +3009,9 @@ static int copy_buf_to_bvec_iter(const struct bio_vec *bvec,
 	return ret;
 }
 
-static int copy_clu_part_to_qio(struct qcow2 *qcow2, const void *buf, struct qio *qio)
+static int copy_clu_part_to_qio(const void *buf, struct qio *qio)
 {
+	struct qcow2 *qcow2 = qio->qcow2;
 	u32 max, seek, clu_size = qcow2->clu_size;
 
 	seek = bytes_off_in_cluster(qcow2, qio);
@@ -3047,7 +3048,7 @@ static int copy_zcow_slice(loff_t start, loff_t end, void *qio_p,
 	return copy_buf_to_bvec_iter(bvec, &iter, buf + off, clu_size - off);
 }
 
-static int prepare_zcow_slices(struct qcow2 *qcow2, void *buf, struct qio *qio)
+static int prepare_zcow_slices(void *buf, struct qio *qio)
 {
 	loff_t consumed = 0;
 	/* Place required slices in that pages like further COW expects */
@@ -3655,46 +3656,59 @@ static int complete_metadata_writeback(struct qcow2 *qcow2)
 }
 
 /* Process completed compressed READs */
-static void process_compressed_read(struct qcow2 *qcow2, struct list_head *read_list,
+static void process_compressed_read(struct list_head *read_list,
 				    struct list_head *cow_list)
 {
+	struct qcow2 *qcow2, *qcow2_prev = NULL;
 	struct qcow2_bvec *qvec;
 	struct qio_ext *ext;
 	int ret;
 	void *buf = NULL, *arg;
 	struct qio *qio;
 	bool for_cow;
+	size_t dctxlen_alloced = 0;
 	size_t dctxlen;
 
 	if (list_empty(read_list))
 		return;
 
-	if (qcow2->hdr.compression_type == QCOW2_COMPRESSION_TYPE_ZSTD)
-		dctxlen = zstd_dstream_workspace_bound(qcow2->clu_size);
-	else
-		dctxlen = zlib_inflate_workspacesize();
-
-
-	buf = kvmalloc(qcow2->clu_size + dctxlen, GFP_NOIO);
-	if (!buf) {
-		end_qios(read_list, BLK_STS_RESOURCE);
-		return;
-	}
-
-	if (qcow2->hdr.compression_type == QCOW2_COMPRESSION_TYPE_ZSTD) {
-		arg = zstd_init_dstream(qcow2->clu_size, buf + qcow2->clu_size, dctxlen);
-		if (!arg) {
-			end_qios(read_list, BLK_STS_RESOURCE);
-			kvfree(buf);
-			return;
-		}
-	} else {
-		arg = buf + qcow2->clu_size;
-	}
 
 	while ((qio = qio_list_pop(read_list)) != NULL) {
 		qvec = qio->data;
 		ext = qio->ext;
+		qcow2 = qio->qcow2;
+
+		if (!qcow2_prev || qcow2_prev != qcow2) {
+			if (qcow2->hdr.compression_type == QCOW2_COMPRESSION_TYPE_ZSTD)
+				dctxlen = zstd_dstream_workspace_bound(qcow2->clu_size);
+			else
+				dctxlen = zlib_inflate_workspacesize();
+
+			if (dctxlen_alloced < dctxlen) {
+				if (buf)
+					kfree(buf);
+				buf = kvmalloc(qcow2->clu_size + dctxlen, GFP_NOIO);
+				if (!buf) {
+					QC_ERR(qcow2->tgt->ti, "can not allocate decompression buffer:%d",
+						   qcow2->clu_size + dctxlen);
+					end_qios(read_list, BLK_STS_RESOURCE);
+					return;
+				}
+				dctxlen_alloced = dctxlen;
+			}
+
+			if (qcow2->hdr.compression_type == QCOW2_COMPRESSION_TYPE_ZSTD) {
+				arg = zstd_init_dstream(qcow2->clu_size, buf + qcow2->clu_size, dctxlen);
+				if (!arg) {
+					end_qios(read_list, BLK_STS_RESOURCE);
+					kvfree(buf);
+					return;
+				}
+			} else {
+				arg = buf + qcow2->clu_size;
+			}
+		}
+		qcow2_prev = qcow2;
 
 		ret = extract_one_compressed(qcow2, buf, qvec,
 				    ext->zdata_off, qio->ret, arg);
@@ -3703,9 +3717,9 @@ static void process_compressed_read(struct qcow2 *qcow2, struct list_head *read_
 
 		for_cow = op_is_write(qio->bi_op);
 		if (!for_cow)
-			ret = copy_clu_part_to_qio(qcow2, buf, qio);
+			ret = copy_clu_part_to_qio(buf, qio);
 		else
-			ret = prepare_zcow_slices(qcow2, buf, qio);
+			ret = prepare_zcow_slices(buf, qio);
 
 		if (!for_cow || ret) {
 err:
@@ -4099,7 +4113,7 @@ void do_qcow2_work(struct work_struct *ws)
 
 	process_embedded_qios(qcow2, &embedded_qios, &deferred_qios);
 	process_deferred_qios(qcow2, &deferred_qios);
-	process_compressed_read(qcow2, &zread_qios, &cow_data_qios);
+	process_compressed_read(&zread_qios, &cow_data_qios);
 	process_backward_merge_write(qcow2, &bwrite_qios);
 	process_cow_data_write(qcow2, &cow_data_qios);
 	process_cow_indexes_write(qcow2, &cow_indexes_qios);
-- 
2.43.0