| Message ID | 20200813162935.210070-7-kwolf@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | block/export: Add infrastructure and QAPI for block exports | expand |
On 13.08.20 18:29, Kevin Wolf wrote: > 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 <kwolf@redhat.com> > --- > include/block/nbd.h | 4 ++-- > blockdev-nbd.c | 9 +-------- > nbd/server.c | 34 +++++++++++++++++----------------- > qemu-nbd.c | 27 ++++++++++++--------------- > 4 files changed, 32 insertions(+), 42 deletions(-) Reviewed-by: Max Reitz <mreitz@redhat.com>
On 13.08.20 18:29, Kevin Wolf wrote: > 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 <kwolf@redhat.com> > --- > include/block/nbd.h | 4 ++-- > blockdev-nbd.c | 9 +-------- > nbd/server.c | 34 +++++++++++++++++----------------- > qemu-nbd.c | 27 ++++++++++++--------------- > 4 files changed, 32 insertions(+), 42 deletions(-) [...] > diff --git a/nbd/server.c b/nbd/server.c > index 774325dbe5..92360d1f08 100644 > --- a/nbd/server.c > +++ b/nbd/server.c [...] > @@ -1569,7 +1574,7 @@ 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); > + assert(size <= INT64_MAX); Forgot to note: I think we can drop this assertion altogether now. Max
On Thu, Aug 13, 2020 at 7:36 PM Kevin Wolf <kwolf@redhat.com> wrote: > 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. > Just to make sure I understand this correctly - qemu-nbd can work with: $ qemu-nbd 'json:{"driver": "file", "filename": "test.raw"}' And: $ qemu-nbd 'json:{"driver": "raw", "file": {"driver": "file", "filename": "test.raw"}}' I assumed that we always create the raw node? oVirt always uses the second form to make it easier to support offset, size, and backing. https://github.com/oVirt/ovirt-imageio/blob/2021164d064227d7c5e03c8da087adc66e3a577e/daemon/ovirt_imageio/_internal/qemu_nbd.py#L104 This also seems to be the way libvirt builds the nodes using -blockdev. Do we have a way to visualize the internal node graph used by qemu-nbd/qemu-img? Nir Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > include/block/nbd.h | 4 ++-- > blockdev-nbd.c | 9 +-------- > nbd/server.c | 34 +++++++++++++++++----------------- > qemu-nbd.c | 27 ++++++++++++--------------- > 4 files changed, 32 insertions(+), 42 deletions(-) > > diff --git a/include/block/nbd.h b/include/block/nbd.h > index c8c5cb6b61..3846d2bac8 100644 > --- a/include/block/nbd.h > +++ b/include/block/nbd.h > @@ -329,8 +329,8 @@ 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/blockdev-nbd.c b/blockdev-nbd.c > index a1dc11bdd7..16cda3b052 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/nbd/server.c b/nbd/server.c > index 774325dbe5..92360d1f08 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 +1574,7 @@ 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); > + assert(size <= INT64_MAX); > exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE); > > if (bitmap) { > @@ -1928,8 +1933,7 @@ 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 +2307,7 @@ 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 +2342,7 @@ 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 +2373,7 @@ 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); > > @@ -2386,8 +2388,7 @@ static coroutine_fn int nbd_handle_request(NBDClient > *client, > if (request->flags & NBD_CMD_FLAG_FAST_ZERO) { > flags |= BDRV_REQ_NO_FALLBACK; > } > - ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset, > - request->len, flags); > + ret = blk_pwrite_zeroes(exp->blk, request->from, request->len, > flags); > return nbd_send_generic_reply(client, request->handle, ret, > "writing to file failed", errp); > > @@ -2401,8 +2402,7 @@ static coroutine_fn int nbd_handle_request(NBDClient > *client, > "flush failed", errp); > > case NBD_CMD_TRIM: > - ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset, > - request->len); > + ret = blk_co_pdiscard(exp->blk, request->from, request->len); > if (ret == 0 && request->flags & NBD_CMD_FLAG_FUA) { > ret = blk_co_flush(exp->blk); > } > diff --git a/qemu-nbd.c b/qemu-nbd.c > index d2657b8db5..818c3f5d46 100644 > --- a/qemu-nbd.c > +++ b/qemu-nbd.c > @@ -523,7 +523,6 @@ 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"; > @@ -1028,6 +1027,17 @@ 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) { > @@ -1045,21 +1055,8 @@ 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); > -- > 2.25.4 > > >
Am 17.08.2020 um 19:19 hat Nir Soffer geschrieben: > On Thu, Aug 13, 2020 at 7:36 PM Kevin Wolf <kwolf@redhat.com> wrote: > > > 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. > > > > Just to make sure I understand this correctly - > > qemu-nbd can work with: > > $ qemu-nbd 'json:{"driver": "file", "filename": "test.raw"}' > > And: > > $ qemu-nbd 'json:{"driver": "raw", "file": {"driver": "file", > "filename": "test.raw"}}' > > I assumed that we always create the raw node? No, the first form creates only the 'file' node without a 'raw' node on top. For all practical matters, this should be the same in qemu-img or qemu-nbd. For actually running VMs, omitting the 'raw' node where it's not needed can improve performance a little. What is true is that if you use a filename without specifying the driver (i.e. you rely on format probing), you'll get a 'raw' node on top of the 'file' node. > oVirt always uses the second form to make it easier to support offset, > size, and backing. > https://github.com/oVirt/ovirt-imageio/blob/2021164d064227d7c5e03c8da087adc66e3a577e/daemon/ovirt_imageio/_internal/qemu_nbd.py#L104 > > This also seems to be the way libvirt builds the nodes using -blockdev. libvirt actually has a BZ to avoid the 'raw' node for performance when it's not needed. > Do we have a way to visualize the internal node graph used by > qemu-nbd/qemu-img? No, but as long as you explicitly specify the driver, you get exactly what you specified. For exploring what happens, you can pass the same json: filename to QEMU (maybe with -hda) and then use the monitor to inspect the state. Kevin
On Tue, Aug 18, 2020 at 11:47 AM Kevin Wolf <kwolf@redhat.com> wrote: > Am 17.08.2020 um 19:19 hat Nir Soffer geschrieben: > > On Thu, Aug 13, 2020 at 7:36 PM Kevin Wolf <kwolf@redhat.com> wrote: > > > > > 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. > > > > > > > Just to make sure I understand this correctly - > > > > qemu-nbd can work with: > > > > $ qemu-nbd 'json:{"driver": "file", "filename": "test.raw"}' > > > > And: > > > > $ qemu-nbd 'json:{"driver": "raw", "file": {"driver": "file", > > "filename": "test.raw"}}' > > > > I assumed that we always create the raw node? > > No, the first form creates only the 'file' node without a 'raw' node on > top. For all practical matters, this should be the same in qemu-img or > qemu-nbd. For actually running VMs, omitting the 'raw' node where it's > not needed can improve performance a little. > We did not check if we have different performance with the extra raw node. Since in our use case (copying images) small reads/writes are unlikely, I don't think it will make a difference. What is true is that if you use a filename without specifying the driver > (i.e. you rely on format probing), you'll get a 'raw' node on top of > the 'file' node. > > > oVirt always uses the second form to make it easier to support offset, > > size, and backing. > > > https://github.com/oVirt/ovirt-imageio/blob/2021164d064227d7c5e03c8da087adc66e3a577e/daemon/ovirt_imageio/_internal/qemu_nbd.py#L104 > > > > This also seems to be the way libvirt builds the nodes using -blockdev. > > libvirt actually has a BZ to avoid the 'raw' node for performance when > it's not needed. > > > Do we have a way to visualize the internal node graph used by > > qemu-nbd/qemu-img? > > No, but as long as you explicitly specify the driver, you get exactly > what you specified. > So this is not really needed then. > For exploring what happens, you can pass the same json: filename to QEMU > (maybe with -hda) and then use the monitor to inspect the state. > > Kevin > >
On 8/13/20 11:29 AM, Kevin Wolf wrote: > 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. Yay! This patch alone is worth having, regardless of the fate of the rest of the series: no change in end-user functionality, but by making qemu-nbd turn it into proper syntactic sugar, we've reduced the maintenance burden of duplicated code. > > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > include/block/nbd.h | 4 ++-- > blockdev-nbd.c | 9 +-------- > nbd/server.c | 34 +++++++++++++++++----------------- > qemu-nbd.c | 27 ++++++++++++--------------- > 4 files changed, 32 insertions(+), 42 deletions(-) > > +++ b/nbd/server.c > @@ -89,7 +89,6 @@ struct NBDExport { > BlockBackend *blk; > char *name; > char *description; > - uint64_t dev_offset; > uint64_t size; I'm trying to figure out if we can also drop 'size' here. If we do, the consequence would be that an NBD client could ask for beyond-EOF I/O, and presumably the block layer would reject that gracefully (although not necessarily with the same errno as NBD currently reports). I'm fine leaving it alone in this patch, though. > @@ -1569,7 +1574,7 @@ 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); > + assert(size <= INT64_MAX); As Max caught, this is now dead code. > @@ -2386,8 +2388,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, > if (request->flags & NBD_CMD_FLAG_FAST_ZERO) { > flags |= BDRV_REQ_NO_FALLBACK; > } > - ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset, > - request->len, flags); > + ret = blk_pwrite_zeroes(exp->blk, request->from, request->len, flags); > return nbd_send_generic_reply(client, request->handle, ret, > "writing to file failed", errp); > > @@ -2401,8 +2402,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, > "flush failed", errp); > > case NBD_CMD_TRIM: > - ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset, > - request->len); > + ret = blk_co_pdiscard(exp->blk, request->from, request->len); Merge conflicts with 890cbccb08; should be obvious enough to resolve, though. > +++ b/qemu-nbd.c > @@ -523,7 +523,6 @@ 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"; > @@ -1028,6 +1027,17 @@ 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); Huh. When 0bc16997f5 got rid of the --partition option, it also got rid of the only way that the NBD driver could clamp down requests to a range smaller than the end of the file. Now that you are adding a raw driver in the mix, that ability to clamp the end of the range (aka a --size option, in addition to an --offset option) may be worth reinstating. But that can be done as a separate patch, if at all (and whether qemu-nbd should do it, or qemu-storage-daemon, or whether we just point people at 'nbdkit --filter=partition', is part of that discussion). But for this patch, it looks like you are making a straight-across conversion. > + bs = bdrv_open(NULL, NULL, raw_opts, flags, &error_fatal); > + blk_remove_bs(blk); > + blk_insert_bs(blk, bs, &error_fatal); > + bdrv_unref(bs); > + } > + Slick. Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/include/block/nbd.h b/include/block/nbd.h index c8c5cb6b61..3846d2bac8 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -329,8 +329,8 @@ 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/blockdev-nbd.c b/blockdev-nbd.c index a1dc11bdd7..16cda3b052 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/nbd/server.c b/nbd/server.c index 774325dbe5..92360d1f08 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 +1574,7 @@ 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); + assert(size <= INT64_MAX); exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE); if (bitmap) { @@ -1928,8 +1933,7 @@ 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 +2307,7 @@ 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 +2342,7 @@ 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 +2373,7 @@ 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); @@ -2386,8 +2388,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, if (request->flags & NBD_CMD_FLAG_FAST_ZERO) { flags |= BDRV_REQ_NO_FALLBACK; } - ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset, - request->len, flags); + ret = blk_pwrite_zeroes(exp->blk, request->from, request->len, flags); return nbd_send_generic_reply(client, request->handle, ret, "writing to file failed", errp); @@ -2401,8 +2402,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, "flush failed", errp); case NBD_CMD_TRIM: - ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset, - request->len); + ret = blk_co_pdiscard(exp->blk, request->from, request->len); if (ret == 0 && request->flags & NBD_CMD_FLAG_FUA) { ret = blk_co_flush(exp->blk); } diff --git a/qemu-nbd.c b/qemu-nbd.c index d2657b8db5..818c3f5d46 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -523,7 +523,6 @@ 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"; @@ -1028,6 +1027,17 @@ 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) { @@ -1045,21 +1055,8 @@ 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);
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 <kwolf@redhat.com> --- include/block/nbd.h | 4 ++-- blockdev-nbd.c | 9 +-------- nbd/server.c | 34 +++++++++++++++++----------------- qemu-nbd.c | 27 ++++++++++++--------------- 4 files changed, 32 insertions(+), 42 deletions(-)