From bae127d4dcf6158c5042e2eee9582430839a9967 Mon Sep 17 00:00:00 2001 From: Antoine Damhet Date: Fri, 17 Jul 2020 15:56:04 +0200 Subject: [PATCH 1/3] file-posix: Handle `EINVAL` fallocate return value The `detect-zeroes=unmap` option may issue unaligned `FALLOC_FL_PUNCH_HOLE` requests, raw block devices can (and will) return `EINVAL`, qemu should then write the zeroes to the blockdev instead of issuing an `IO_ERROR`. The problem can be reprodced like this: $ qemu-io -c 'write -P 0 42 1234' --image-opts driver=host_device,filename=/dev/loop0,detect-zeroes=unmap write failed: Invalid argument Signed-off-by: Antoine Damhet Message-Id: <20200717135603.51180-1-antoine.damhet@blade-group.com> Signed-off-by: Kevin Wolf --- block/file-posix.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index 8cc39a1ef6..9a00d4190a 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1698,7 +1698,11 @@ static int handle_aiocb_write_zeroes_unmap(void *opaque) #ifdef CONFIG_FALLOCATE_PUNCH_HOLE int ret = do_fallocate(s->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, aiocb->aio_offset, aiocb->aio_nbytes); - if (ret != -ENOTSUP) { + switch (ret) { + case -ENOTSUP: + case -EINVAL: + break; + default: return ret; } #endif From 61b3043965fe3552ee2684a97e7cc809ca7a71b3 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 21 Jul 2020 15:55:19 +0200 Subject: [PATCH 2/3] qcow2: Implement v2 zero writes with discard if possible qcow2 version 2 images don't support the zero flag for clusters, so for write_zeroes requests, we return -ENOTSUP and get explicit zero buffer writes. If the image doesn't have a backing file, we can do better: Just discard the respective clusters. This is relevant for 'qemu-img convert -O qcow2 -n', where qemu-img has to assume that the existing target image may contain any data, so it has to write zeroes. Without this patch, this results in a fully allocated target image, even if the source image was empty. Reported-by: Nir Soffer Signed-off-by: Kevin Wolf Message-Id: <20200721135520.72355-2-kwolf@redhat.com> Reviewed-by: Max Reitz Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 4b5fc8c4a7..a677ba9f5c 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1797,8 +1797,15 @@ int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || end_offset >= bs->total_sectors << BDRV_SECTOR_BITS); - /* The zero flag is only supported by version 3 and newer */ + /* + * The zero flag is only supported by version 3 and newer. However, if we + * have no backing file, we can resort to discard in version 2. + */ if (s->qcow_version < 3) { + if (!bs->backing) { + return qcow2_cluster_discard(bs, offset, bytes, + QCOW2_DISCARD_REQUEST, false); + } return -ENOTSUP; } From 4a01e27ddcb5921efd68820d05d85ba71293fea6 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 21 Jul 2020 15:55:20 +0200 Subject: [PATCH 3/3] iotests: Test sparseness for qemu-img convert -n Signed-off-by: Kevin Wolf Message-Id: <20200721135520.72355-3-kwolf@redhat.com> Reviewed-by: Max Reitz Signed-off-by: Kevin Wolf --- tests/qemu-iotests/122 | 30 ++++++++++++++++++++++++++++++ tests/qemu-iotests/122.out | 17 +++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/tests/qemu-iotests/122 b/tests/qemu-iotests/122 index dfd1cd05d6..0f3d4ca851 100755 --- a/tests/qemu-iotests/122 +++ b/tests/qemu-iotests/122 @@ -281,6 +281,36 @@ $QEMU_IMG convert -O $IMGFMT -n "$TEST_IMG" "$TEST_IMG".orig $QEMU_IMG compare "$TEST_IMG" "$TEST_IMG".orig +echo +echo '=== -n to an empty image ===' +echo + +TEST_IMG="$TEST_IMG".orig _make_test_img 64M + +# Convert with -n, which should not result in a fully allocated image, not even +# with compat=0.10 (because the target doesn't have a backing file) +for compat in "1.1" "0.10"; do + IMGOPTS="compat=$compat" _make_test_img 64M + $QEMU_IMG convert -O $IMGFMT -n "$TEST_IMG".orig "$TEST_IMG" + $QEMU_IMG map --output=json "$TEST_IMG" +done + +echo +echo '=== -n to an empty image with a backing file ===' +echo + +TEST_IMG="$TEST_IMG".orig _make_test_img 64M +TEST_IMG="$TEST_IMG".base _make_test_img 64M + +# Convert with -n, which should still not result in a fully allocated image for +# compat=1.1 (because it can use zero clusters), but it should be fully +# allocated with compat=0.10 +for compat in "1.1" "0.10"; do + IMGOPTS="compat=$compat" _make_test_img -b "$TEST_IMG".base -F $IMGFMT 64M + $QEMU_IMG convert -O $IMGFMT -n "$TEST_IMG".orig "$TEST_IMG" + $QEMU_IMG map --output=json "$TEST_IMG" +done + echo echo '=== -n -B to an image without a backing file ===' echo diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out index f1f195ed77..3a3e121d57 100644 --- a/tests/qemu-iotests/122.out +++ b/tests/qemu-iotests/122.out @@ -229,6 +229,23 @@ wrote 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) Images are identical. +=== -n to an empty image === + +Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=67108864 +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 +[{ "start": 0, "length": 67108864, "depth": 0, "zero": true, "data": false}] +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 +[{ "start": 0, "length": 67108864, "depth": 0, "zero": true, "data": false}] + +=== -n to an empty image with a backing file === + +Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=67108864 +Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864 +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT +[{ "start": 0, "length": 67108864, "depth": 0, "zero": true, "data": false}] +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT +[{ "start": 0, "length": 67108864, "depth": 0, "zero": false, "data": true, "offset": 327680}] + === -n -B to an image without a backing file === Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864