From 882d09226b7f45b72c5b7763c4c4aba182e0f8a1 Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Wed, 11 Mar 2020 10:51:43 +0000 Subject: [PATCH 02/20] block: Generic file creation fallback RH-Author: Maxim Levitsky Message-id: <20200311105147.13208-3-mlevitsk@redhat.com> Patchwork-id: 94227 O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH v2 2/6] block: Generic file creation fallback Bugzilla: 1640894 RH-Acked-by: Stefano Garzarella RH-Acked-by: John Snow RH-Acked-by: Max Reitz From: Max Reitz If a protocol driver does not support image creation, we can see whether maybe the file exists already. If so, just truncating it will be sufficient. Signed-off-by: Max Reitz Message-Id: <20200122164532.178040-3-mreitz@redhat.com> Signed-off-by: Max Reitz (cherry picked from commit fd17146cd93d1704cd96d7c2757b325fc7aac6fd) Signed-off-by: Maxim Levitsky Signed-off-by: Danilo C. L. de Paula --- block.c | 159 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 147 insertions(+), 12 deletions(-) diff --git a/block.c b/block.c index 2e5e8b6..3beec7f 100644 --- a/block.c +++ b/block.c @@ -532,20 +532,139 @@ out: return ret; } -int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp) +/** + * Helper function for bdrv_create_file_fallback(): Resize @blk to at + * least the given @minimum_size. + * + * On success, return @blk's actual length. + * Otherwise, return -errno. + */ +static int64_t create_file_fallback_truncate(BlockBackend *blk, + int64_t minimum_size, Error **errp) { - BlockDriver *drv; + Error *local_err = NULL; + int64_t size; + int ret; + + ret = blk_truncate(blk, minimum_size, false, PREALLOC_MODE_OFF, &local_err); + if (ret < 0 && ret != -ENOTSUP) { + error_propagate(errp, local_err); + return ret; + } + + size = blk_getlength(blk); + if (size < 0) { + error_free(local_err); + error_setg_errno(errp, -size, + "Failed to inquire the new image file's length"); + return size; + } + + if (size < minimum_size) { + /* Need to grow the image, but we failed to do that */ + error_propagate(errp, local_err); + return -ENOTSUP; + } + + error_free(local_err); + local_err = NULL; + + return size; +} + +/** + * Helper function for bdrv_create_file_fallback(): Zero the first + * sector to remove any potentially pre-existing image header. + */ +static int create_file_fallback_zero_first_sector(BlockBackend *blk, + int64_t current_size, + Error **errp) +{ + int64_t bytes_to_clear; + int ret; + + bytes_to_clear = MIN(current_size, BDRV_SECTOR_SIZE); + if (bytes_to_clear) { + ret = blk_pwrite_zeroes(blk, 0, bytes_to_clear, BDRV_REQ_MAY_UNMAP); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to clear the new image's first sector"); + return ret; + } + } + + return 0; +} + +static int bdrv_create_file_fallback(const char *filename, BlockDriver *drv, + QemuOpts *opts, Error **errp) +{ + BlockBackend *blk; + QDict *options = qdict_new(); + int64_t size = 0; + char *buf = NULL; + PreallocMode prealloc; Error *local_err = NULL; int ret; + size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0); + buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC); + prealloc = qapi_enum_parse(&PreallocMode_lookup, buf, + PREALLOC_MODE_OFF, &local_err); + g_free(buf); + if (local_err) { + error_propagate(errp, local_err); + return -EINVAL; + } + + if (prealloc != PREALLOC_MODE_OFF) { + error_setg(errp, "Unsupported preallocation mode '%s'", + PreallocMode_str(prealloc)); + return -ENOTSUP; + } + + qdict_put_str(options, "driver", drv->format_name); + + blk = blk_new_open(filename, NULL, options, + BDRV_O_RDWR | BDRV_O_RESIZE, errp); + if (!blk) { + error_prepend(errp, "Protocol driver '%s' does not support image " + "creation, and opening the image failed: ", + drv->format_name); + return -EINVAL; + } + + size = create_file_fallback_truncate(blk, size, errp); + if (size < 0) { + ret = size; + goto out; + } + + ret = create_file_fallback_zero_first_sector(blk, size, errp); + if (ret < 0) { + goto out; + } + + ret = 0; +out: + blk_unref(blk); + return ret; +} + +int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp) +{ + BlockDriver *drv; + drv = bdrv_find_protocol(filename, true, errp); if (drv == NULL) { return -ENOENT; } - ret = bdrv_create(drv, filename, opts, &local_err); - error_propagate(errp, local_err); - return ret; + if (drv->bdrv_co_create_opts) { + return bdrv_create(drv, filename, opts, errp); + } else { + return bdrv_create_file_fallback(filename, drv, opts, errp); + } } /** @@ -1422,6 +1541,24 @@ QemuOptsList bdrv_runtime_opts = { }, }; +static QemuOptsList fallback_create_opts = { + .name = "fallback-create-opts", + .head = QTAILQ_HEAD_INITIALIZER(fallback_create_opts.head), + .desc = { + { + .name = BLOCK_OPT_SIZE, + .type = QEMU_OPT_SIZE, + .help = "Virtual disk size" + }, + { + .name = BLOCK_OPT_PREALLOC, + .type = QEMU_OPT_STRING, + .help = "Preallocation mode (allowed values: off)" + }, + { /* end of list */ } + } +}; + /* * Common part for opening disk images and files * @@ -5743,14 +5880,12 @@ void bdrv_img_create(const char *filename, const char *fmt, return; } - if (!proto_drv->create_opts) { - error_setg(errp, "Protocol driver '%s' does not support image creation", - proto_drv->format_name); - return; - } - create_opts = qemu_opts_append(create_opts, drv->create_opts); - create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); + if (proto_drv->create_opts) { + create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); + } else { + create_opts = qemu_opts_append(create_opts, &fallback_create_opts); + } /* Create parameter list with default values */ opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); -- 1.8.3.1