From 168468fe19c872d31d17581e6a6cf7b69bd105b1 Mon Sep 17 00:00:00 2001 From: David Edmondson Date: Wed, 5 Feb 2020 11:02:48 +0000 Subject: qemu-img: Add --target-is-zero to convert In many cases the target of a convert operation is a newly provisioned target that the user knows is blank (reads as zero). In this situation there is no requirement for qemu-img to wastefully zero out the entire device. Add a new option, --target-is-zero, allowing the user to indicate that an existing target device will return zeros for all reads. Signed-off-by: David Edmondson Message-Id: <20200205110248.2009589-2-david.edmondson@oracle.com> Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Eric Blake Signed-off-by: Max Reitz --- qemu-img.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'qemu-img.c') diff --git a/qemu-img.c b/qemu-img.c index 2b4562b..0faf2cd 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -70,6 +70,7 @@ enum { OPTION_PREALLOCATION = 265, OPTION_SHRINK = 266, OPTION_SALVAGE = 267, + OPTION_TARGET_IS_ZERO = 268, }; typedef enum OutputFormat { @@ -1984,10 +1985,9 @@ static int convert_do_copy(ImgConvertState *s) int64_t sector_num = 0; /* Check whether we have zero initialisation or can get it efficiently */ - if (s->target_is_new && s->min_sparse && !s->target_has_backing) { + if (!s->has_zero_init && s->target_is_new && s->min_sparse && + !s->target_has_backing) { s->has_zero_init = bdrv_has_zero_init(blk_bs(s->target)); - } else { - s->has_zero_init = false; } if (!s->has_zero_init && !s->target_has_backing && @@ -2086,6 +2086,7 @@ static int img_convert(int argc, char **argv) {"force-share", no_argument, 0, 'U'}, {"target-image-opts", no_argument, 0, OPTION_TARGET_IMAGE_OPTS}, {"salvage", no_argument, 0, OPTION_SALVAGE}, + {"target-is-zero", no_argument, 0, OPTION_TARGET_IS_ZERO}, {0, 0, 0, 0} }; c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU", @@ -2209,6 +2210,14 @@ static int img_convert(int argc, char **argv) case OPTION_TARGET_IMAGE_OPTS: tgt_image_opts = true; break; + case OPTION_TARGET_IS_ZERO: + /* + * The user asserting that the target is blank has the + * same effect as the target driver supporting zero + * initialisation. + */ + s.has_zero_init = true; + break; } } @@ -2247,6 +2256,11 @@ static int img_convert(int argc, char **argv) warn_report("This will become an error in future QEMU versions."); } + if (s.has_zero_init && !skip_create) { + error_report("--target-is-zero requires use of -n flag"); + goto fail_getopt; + } + s.src_num = argc - optind - 1; out_filename = s.src_num >= 1 ? argv[argc - 1] : NULL; @@ -2380,6 +2394,12 @@ static int img_convert(int argc, char **argv) } s.target_has_backing = (bool) out_baseimg; + if (s.has_zero_init && s.target_has_backing) { + error_report("Cannot use --target-is-zero when the destination " + "image has a backing file"); + goto out; + } + if (s.src_num > 1 && out_baseimg) { error_report("Having a backing file for the target makes no sense when " "concatenating multiple input images"); -- cgit v1.1