diff options
Diffstat (limited to 'block/qcow2-threads.c')
| -rw-r--r-- | block/qcow2-threads.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c index 7dbaf53..1914baf 100644 --- a/block/qcow2-threads.c +++ b/block/qcow2-threads.c @@ -28,6 +28,11 @@ #define ZLIB_CONST #include <zlib.h> +#ifdef CONFIG_ZSTD +#include <zstd.h> +#include <zstd_errors.h> +#endif + #include "qcow2.h" #include "block/thread-pool.h" #include "crypto.h" @@ -166,6 +171,160 @@ static ssize_t qcow2_zlib_decompress(void *dest, size_t dest_size, return ret; } +#ifdef CONFIG_ZSTD + +/* + * qcow2_zstd_compress() + * + * Compress @src_size bytes of data using zstd compression method + * + * @dest - destination buffer, @dest_size bytes + * @src - source buffer, @src_size bytes + * + * Returns: compressed size on success + * -ENOMEM destination buffer is not enough to store compressed data + * -EIO on any other error + */ +static ssize_t qcow2_zstd_compress(void *dest, size_t dest_size, + const void *src, size_t src_size) +{ + ssize_t ret; + size_t zstd_ret; + ZSTD_outBuffer output = { + .dst = dest, + .size = dest_size, + .pos = 0 + }; + ZSTD_inBuffer input = { + .src = src, + .size = src_size, + .pos = 0 + }; + ZSTD_CCtx *cctx = ZSTD_createCCtx(); + + if (!cctx) { + return -EIO; + } + /* + * Use the zstd streamed interface for symmetry with decompression, + * where streaming is essential since we don't record the exact + * compressed size. + * + * ZSTD_compressStream2() tries to compress everything it could + * with a single call. Although, ZSTD docs says that: + * "You must continue calling ZSTD_compressStream2() with ZSTD_e_end + * until it returns 0, at which point you are free to start a new frame", + * in out tests we saw the only case when it returned with >0 - + * when the output buffer was too small. In that case, + * ZSTD_compressStream2() expects a bigger buffer on the next call. + * We can't provide a bigger buffer because we are limited with dest_size + * which we pass to the ZSTD_compressStream2() at once. + * So, we don't need any loops and just abort the compression when we + * don't get 0 result on the first call. + */ + zstd_ret = ZSTD_compressStream2(cctx, &output, &input, ZSTD_e_end); + + if (zstd_ret) { + if (zstd_ret > output.size - output.pos) { + ret = -ENOMEM; + } else { + ret = -EIO; + } + goto out; + } + + /* make sure that zstd didn't overflow the dest buffer */ + assert(output.pos <= dest_size); + ret = output.pos; +out: + ZSTD_freeCCtx(cctx); + return ret; +} + +/* + * qcow2_zstd_decompress() + * + * Decompress some data (not more than @src_size bytes) to produce exactly + * @dest_size bytes using zstd compression method + * + * @dest - destination buffer, @dest_size bytes + * @src - source buffer, @src_size bytes + * + * Returns: 0 on success + * -EIO on any error + */ +static ssize_t qcow2_zstd_decompress(void *dest, size_t dest_size, + const void *src, size_t src_size) +{ + size_t zstd_ret = 0; + ssize_t ret = 0; + ZSTD_outBuffer output = { + .dst = dest, + .size = dest_size, + .pos = 0 + }; + ZSTD_inBuffer input = { + .src = src, + .size = src_size, + .pos = 0 + }; + ZSTD_DCtx *dctx = ZSTD_createDCtx(); + + if (!dctx) { + return -EIO; + } + + /* + * The compressed stream from the input buffer may consist of more + * than one zstd frame. So we iterate until we get a fully + * uncompressed cluster. + * From zstd docs related to ZSTD_decompressStream: + * "return : 0 when a frame is completely decoded and fully flushed" + * We suppose that this means: each time ZSTD_decompressStream reads + * only ONE full frame and returns 0 if and only if that frame + * is completely decoded and flushed. Only after returning 0, + * ZSTD_decompressStream reads another ONE full frame. + */ + while (output.pos < output.size) { + size_t last_in_pos = input.pos; + size_t last_out_pos = output.pos; + zstd_ret = ZSTD_decompressStream(dctx, &output, &input); + + if (ZSTD_isError(zstd_ret)) { + ret = -EIO; + break; + } + + /* + * The ZSTD manual is vague about what to do if it reads + * the buffer partially, and we don't want to get stuck + * in an infinite loop where ZSTD_decompressStream + * returns > 0 waiting for another input chunk. So, we add + * a check which ensures that the loop makes some progress + * on each step. + */ + if (last_in_pos >= input.pos && + last_out_pos >= output.pos) { + ret = -EIO; + break; + } + } + /* + * Make sure that we have the frame fully flushed here + * if not, we somehow managed to get uncompressed cluster + * greater then the cluster size, possibly because of its + * damage. + */ + if (zstd_ret > 0) { + ret = -EIO; + } + + ZSTD_freeDCtx(dctx); + assert(ret == 0 || ret == -EIO); + return ret; +} +#endif + static int qcow2_compress_pool_func(void *opaque) { Qcow2CompressData *data = opaque; @@ -217,6 +376,11 @@ qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size, fn = qcow2_zlib_compress; break; +#ifdef CONFIG_ZSTD + case QCOW2_COMPRESSION_TYPE_ZSTD: + fn = qcow2_zstd_compress; + break; +#endif default: abort(); } @@ -249,6 +413,11 @@ qcow2_co_decompress(BlockDriverState *bs, void *dest, size_t dest_size, fn = qcow2_zlib_decompress; break; +#ifdef CONFIG_ZSTD + case QCOW2_COMPRESSION_TYPE_ZSTD: + fn = qcow2_zstd_decompress; + break; +#endif default: abort(); } |