diff options
| -rw-r--r-- | qemu-img-cmds.hx | 4 | ||||
| -rw-r--r-- | qemu-img.c | 61 | ||||
| -rw-r--r-- | qemu-img.texi | 7 |
3 files changed, 67 insertions, 5 deletions
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx index 1299e83..4be00a5 100644 --- a/qemu-img-cmds.hx +++ b/qemu-img-cmds.hx @@ -28,9 +28,9 @@ STEXI ETEXI DEF("convert", img_convert, - "convert [-c] [-p] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] filename [filename2 [...]] output_filename") + "convert [-c] [-p] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename") STEXI -@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename} +@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename} ETEXI DEF("info", img_info, @@ -82,6 +82,8 @@ static void help(void) " rebasing in this case (useful for renaming the backing file)\n" " '-h' with or without a command shows this help and lists the supported formats\n" " '-p' show progress of command (only certain commands)\n" + " '-S' indicates the consecutive number of bytes that must contain only zeros\n" + " for qemu-img to create a sparse image during conversion\n" "\n" "Parameters to snapshot subcommand:\n" " 'snapshot' is the name of the snapshot to create, apply or delete\n" @@ -571,6 +573,48 @@ static int is_allocated_sectors(const uint8_t *buf, int n, int *pnum) } /* + * Like is_allocated_sectors, but if the buffer starts with a used sector, + * up to 'min' consecutive sectors containing zeros are ignored. This avoids + * breaking up write requests for only small sparse areas. + */ +static int is_allocated_sectors_min(const uint8_t *buf, int n, int *pnum, + int min) +{ + int ret; + int num_checked, num_used; + + if (n < min) { + min = n; + } + + ret = is_allocated_sectors(buf, n, pnum); + if (!ret) { + return ret; + } + + num_used = *pnum; + buf += BDRV_SECTOR_SIZE * *pnum; + n -= *pnum; + num_checked = num_used; + + while (n > 0) { + ret = is_allocated_sectors(buf, n, pnum); + + buf += BDRV_SECTOR_SIZE * *pnum; + n -= *pnum; + num_checked += *pnum; + if (ret) { + num_used = num_checked; + } else if (*pnum >= min) { + break; + } + } + + *pnum = num_used; + return 1; +} + +/* * Compares two buffers sector by sector. Returns 0 if the first sector of both * buffers matches, non-zero otherwise. * @@ -620,6 +664,7 @@ static int img_convert(int argc, char **argv) char *options = NULL; const char *snapshot_name = NULL; float local_progress; + int min_sparse = 8; /* Need at least 4k of zeros for sparse detection */ fmt = NULL; out_fmt = "raw"; @@ -627,7 +672,7 @@ static int img_convert(int argc, char **argv) out_baseimg = NULL; compress = 0; for(;;) { - c = getopt(argc, argv, "f:O:B:s:hce6o:pt:"); + c = getopt(argc, argv, "f:O:B:s:hce6o:pS:t:"); if (c == -1) { break; } @@ -662,6 +707,18 @@ static int img_convert(int argc, char **argv) case 's': snapshot_name = optarg; break; + case 'S': + { + int64_t sval; + sval = strtosz_suffix(optarg, NULL, STRTOSZ_DEFSUFFIX_B); + if (sval < 0) { + error_report("Invalid minimum zero buffer size for sparse output specified"); + return 1; + } + + min_sparse = sval / BDRV_SECTOR_SIZE; + break; + } case 'p': progress = 1; break; @@ -970,7 +1027,7 @@ static int img_convert(int argc, char **argv) sectors that are entirely 0, since whatever data was already there is garbage, not 0s. */ if (!has_zero_init || out_baseimg || - is_allocated_sectors(buf1, n, &n1)) { + is_allocated_sectors_min(buf1, n, &n1, min_sparse)) { ret = bdrv_write(out_bs, sector_num, buf1, n1); if (ret < 0) { error_report("error while writing sector %" PRId64 diff --git a/qemu-img.texi b/qemu-img.texi index 495a1b6..70fa321 100644 --- a/qemu-img.texi +++ b/qemu-img.texi @@ -40,6 +40,11 @@ indicates that target image must be compressed (qcow format only) with or without a command shows help and lists the supported formats @item -p display progress bar (convert and rebase commands only) +@item -S @var{size} +indicates the consecutive number of bytes that must contain only zeros +for qemu-img to create a sparse image during conversion. This value is rounded +down to the nearest 512 bytes. You may use the common size suffixes like +@code{k} for kilobytes. @end table Parameters to snapshot subcommand: @@ -86,7 +91,7 @@ it doesn't need to be specified separately in this case. Commit the changes recorded in @var{filename} in its base image. -@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename} +@item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename} Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c} |
