From b57e4de079d90caca05fed5b45aeb642c6c29aa0 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 24 Sep 2020 17:26:52 +0200 Subject: [PATCH] qemu-nbd: Use raw block driver for --offset Instead of implementing qemu-nbd --offset in the NBD code, just put a raw block node with the requested offset on top of the user image and rely on that doing the job. This does not only simplify the nbd_export_new() interface and bring it closer to the set of options that the nbd-server-add QMP command offers, but in fact it also eliminates a potential source for bugs in the NBD code which previously had to add the offset manually in all relevant places. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Reviewed-by: Eric Blake Message-Id: <20200924152717.287415-7-kwolf@redhat.com> Acked-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- blockdev-nbd.c | 9 +-------- include/block/nbd.h | 4 ++-- nbd/server.c | 33 ++++++++++++++++----------------- qemu-nbd.c | 27 ++++++++++++--------------- 4 files changed, 31 insertions(+), 42 deletions(-) diff --git a/blockdev-nbd.c b/blockdev-nbd.c index 47b04f166a..96cb0100e9 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -154,7 +154,6 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp) BlockDriverState *bs = NULL; BlockBackend *on_eject_blk; NBDExport *exp = NULL; - int64_t len; AioContext *aio_context; assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD); @@ -192,12 +191,6 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp) aio_context = bdrv_get_aio_context(bs); aio_context_acquire(aio_context); - len = bdrv_getlength(bs); - if (len < 0) { - error_setg_errno(errp, -len, - "Failed to determine the NBD export's length"); - goto out; - } if (!arg->has_writable) { arg->writable = false; @@ -206,7 +199,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp) arg->writable = false; } - exp = nbd_export_new(bs, 0, len, arg->name, arg->description, arg->bitmap, + exp = nbd_export_new(bs, arg->name, arg->description, arg->bitmap, !arg->writable, !arg->writable, NULL, false, on_eject_blk, errp); if (!exp) { diff --git a/include/block/nbd.h b/include/block/nbd.h index 7698453fb2..451f399b0a 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -331,8 +331,8 @@ typedef struct NBDExport NBDExport; typedef struct NBDClient NBDClient; BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp); -NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, - uint64_t size, const char *name, const char *desc, +NBDExport *nbd_export_new(BlockDriverState *bs, + const char *name, const char *desc, const char *bitmap, bool readonly, bool shared, void (*close)(NBDExport *), bool writethrough, BlockBackend *on_eject_blk, Error **errp); diff --git a/nbd/server.c b/nbd/server.c index f5af93c253..33aaca918c 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -89,7 +89,6 @@ struct NBDExport { BlockBackend *blk; char *name; char *description; - uint64_t dev_offset; uint64_t size; uint16_t nbdflags; QTAILQ_HEAD(, NBDClient) clients; @@ -1507,8 +1506,8 @@ static void nbd_eject_notifier(Notifier *n, void *data) aio_context_release(aio_context); } -NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, - uint64_t size, const char *name, const char *desc, +NBDExport *nbd_export_new(BlockDriverState *bs, + const char *name, const char *desc, const char *bitmap, bool readonly, bool shared, void (*close)(NBDExport *), bool writethrough, BlockBackend *on_eject_blk, Error **errp) @@ -1516,9 +1515,17 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, AioContext *ctx; BlockBackend *blk; NBDExport *exp; + int64_t size; uint64_t perm; int ret; + size = bdrv_getlength(bs); + if (size < 0) { + error_setg_errno(errp, -size, + "Failed to determine the NBD export's length"); + return NULL; + } + exp = g_new0(NBDExport, 1); exp->common = (BlockExport) { .drv = &blk_exp_nbd, @@ -1553,8 +1560,6 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, exp->refcount = 1; QTAILQ_INIT(&exp->clients); exp->blk = blk; - assert(dev_offset <= INT64_MAX); - exp->dev_offset = dev_offset; exp->name = g_strdup(name); assert(!desc || strlen(desc) <= NBD_MAX_STRING_SIZE); exp->description = g_strdup(desc); @@ -1569,7 +1574,6 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES | NBD_FLAG_SEND_FAST_ZERO); } - assert(size <= INT64_MAX - dev_offset); exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE); if (bitmap) { @@ -1928,8 +1932,7 @@ static int coroutine_fn nbd_co_send_sparse_read(NBDClient *client, stl_be_p(&chunk.length, pnum); ret = nbd_co_send_iov(client, iov, 1, errp); } else { - ret = blk_pread(exp->blk, offset + progress + exp->dev_offset, - data + progress, pnum); + ret = blk_pread(exp->blk, offset + progress, data + progress, pnum); if (ret < 0) { error_setg_errno(errp, -ret, "reading from file failed"); break; @@ -2303,8 +2306,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request, data, request->len, errp); } - ret = blk_pread(exp->blk, request->from + exp->dev_offset, data, - request->len); + ret = blk_pread(exp->blk, request->from, data, request->len); if (ret < 0) { return nbd_send_generic_reply(client, request->handle, ret, "reading from file failed", errp); @@ -2339,7 +2341,7 @@ static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *request, assert(request->type == NBD_CMD_CACHE); - ret = blk_co_preadv(exp->blk, request->from + exp->dev_offset, request->len, + ret = blk_co_preadv(exp->blk, request->from, request->len, NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH); return nbd_send_generic_reply(client, request->handle, ret, @@ -2370,8 +2372,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, if (request->flags & NBD_CMD_FLAG_FUA) { flags |= BDRV_REQ_FUA; } - ret = blk_pwrite(exp->blk, request->from + exp->dev_offset, - data, request->len, flags); + ret = blk_pwrite(exp->blk, request->from, data, request->len, flags); return nbd_send_generic_reply(client, request->handle, ret, "writing to file failed", errp); @@ -2392,8 +2393,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, int align = client->check_align ?: 1; int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES, align)); - ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset, - len, flags); + ret = blk_pwrite_zeroes(exp->blk, request->from, len, flags); request->len -= len; request->from += len; } @@ -2416,8 +2416,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, int align = client->check_align ?: 1; int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES, align)); - ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset, - len); + ret = blk_co_pdiscard(exp->blk, request->from, len); request->len -= len; request->from += len; } diff --git a/qemu-nbd.c b/qemu-nbd.c index e39d3b23c1..16473d809c 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -524,7 +524,6 @@ int main(int argc, char **argv) const char *port = NULL; char *sockpath = NULL; char *device = NULL; - int64_t fd_size; QemuOpts *sn_opts = NULL; const char *sn_id_or_name = NULL; const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:B:L"; @@ -1037,6 +1036,17 @@ int main(int argc, char **argv) } bs = blk_bs(blk); + if (dev_offset) { + QDict *raw_opts = qdict_new(); + qdict_put_str(raw_opts, "driver", "raw"); + qdict_put_str(raw_opts, "file", bs->node_name); + qdict_put_int(raw_opts, "offset", dev_offset); + bs = bdrv_open(NULL, NULL, raw_opts, flags, &error_fatal); + blk_remove_bs(blk); + blk_insert_bs(blk, bs, &error_fatal); + bdrv_unref(bs); + } + blk_set_enable_write_cache(blk, !writethrough); if (sn_opts) { @@ -1054,21 +1064,8 @@ int main(int argc, char **argv) } bs->detect_zeroes = detect_zeroes; - fd_size = blk_getlength(blk); - if (fd_size < 0) { - error_report("Failed to determine the image length: %s", - strerror(-fd_size)); - exit(EXIT_FAILURE); - } - if (dev_offset >= fd_size) { - error_report("Offset (%" PRIu64 ") has to be smaller than the image " - "size (%" PRId64 ")", dev_offset, fd_size); - exit(EXIT_FAILURE); - } - fd_size -= dev_offset; - - export = nbd_export_new(bs, dev_offset, fd_size, export_name, + export = nbd_export_new(bs, export_name, export_description, bitmap, readonly, shared > 1, nbd_export_closed, writethrough, NULL, &error_fatal);