| Message ID | 20221029122031.975273-1-afaria@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | block/blkio: Tolerate device size changes | expand |
On Sat, Oct 29, 2022 at 01:20:31PM +0100, Alberto Faria wrote: > Some libblkio drivers may be able to work with regular files (e.g., > io_uring) or otherwise resizable devices. Conservatively set > BlockDriver::has_variable_length to true to ensure bdrv_nb_sectors() > always gives up-to-date results. > > Also implement BlockDriver::bdrv_co_truncate for the case where no > preallocation is needed and the device already has a size compatible > with what was requested. > > Signed-off-by: Alberto Faria <afaria@redhat.com> > --- > > This is based on Stefan's block tree: > https://gitlab.com/stefanha/qemu/-/commits/block > > block/blkio.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) Thanks, applied to my block tree: https://gitlab.com/stefanha/qemu/commits/block Stefan
Am 29.10.2022 um 14:20 hat Alberto Faria geschrieben: > Some libblkio drivers may be able to work with regular files (e.g., > io_uring) or otherwise resizable devices. Conservatively set > BlockDriver::has_variable_length to true to ensure bdrv_nb_sectors() > always gives up-to-date results. > > Also implement BlockDriver::bdrv_co_truncate for the case where no > preallocation is needed and the device already has a size compatible > with what was requested. > > Signed-off-by: Alberto Faria <afaria@redhat.com> > --- > > This is based on Stefan's block tree: > https://gitlab.com/stefanha/qemu/-/commits/block > > block/blkio.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/block/blkio.c b/block/blkio.c > index 82f26eedd2..190454cdbe 100644 > --- a/block/blkio.c > +++ b/block/blkio.c > @@ -845,6 +845,31 @@ static int64_t blkio_getlength(BlockDriverState *bs) > return capacity; > } > > +static int coroutine_fn blkio_truncate(BlockDriverState *bs, int64_t offset, > + bool exact, PreallocMode prealloc, > + BdrvRequestFlags flags, Error **errp) > +{ > + int64_t current_length; > + > + if (prealloc != PREALLOC_MODE_OFF) { > + error_setg(errp, "Unsupported preallocation mode '%s'", > + PreallocMode_str(prealloc)); > + return -ENOTSUP; > + } > + > + current_length = blkio_getlength(bs); > + > + if (offset > current_length) { > + error_setg(errp, "Cannot grow device"); > + return -EINVAL; > + } else if (exact && offset != current_length) { > + error_setg(errp, "Cannot resize device"); > + return -ENOTSUP; > + } > + > + return 0; > +} > + > static int blkio_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) > { > return 0; > @@ -960,10 +985,12 @@ static void blkio_refresh_limits(BlockDriverState *bs, Error **errp) > { \ > .format_name = name, \ > .protocol_name = name, \ > + .has_variable_length = true, \ I don't think this is a good idea, it will read the capacity from libblkio before every single request, which can't result in good performance. We're generally only using .has_variable_length for removable media on the backend (i.e. for host_cdrom and filters that can potentially sit on top of it, but will used the cached value on the protocol level again for other protocol drivers). If you resize a host_device, you need to use QMP 'block_resize' explicitly. I think it should be the same for libblkio. Kevin
diff --git a/block/blkio.c b/block/blkio.c index 82f26eedd2..190454cdbe 100644 --- a/block/blkio.c +++ b/block/blkio.c @@ -845,6 +845,31 @@ static int64_t blkio_getlength(BlockDriverState *bs) return capacity; } +static int coroutine_fn blkio_truncate(BlockDriverState *bs, int64_t offset, + bool exact, PreallocMode prealloc, + BdrvRequestFlags flags, Error **errp) +{ + int64_t current_length; + + if (prealloc != PREALLOC_MODE_OFF) { + error_setg(errp, "Unsupported preallocation mode '%s'", + PreallocMode_str(prealloc)); + return -ENOTSUP; + } + + current_length = blkio_getlength(bs); + + if (offset > current_length) { + error_setg(errp, "Cannot grow device"); + return -EINVAL; + } else if (exact && offset != current_length) { + error_setg(errp, "Cannot resize device"); + return -ENOTSUP; + } + + return 0; +} + static int blkio_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) { return 0; @@ -960,10 +985,12 @@ static void blkio_refresh_limits(BlockDriverState *bs, Error **errp) { \ .format_name = name, \ .protocol_name = name, \ + .has_variable_length = true, \ .instance_size = sizeof(BDRVBlkioState), \ .bdrv_file_open = blkio_file_open, \ .bdrv_close = blkio_close, \ .bdrv_getlength = blkio_getlength, \ + .bdrv_co_truncate = blkio_truncate, \ .bdrv_get_info = blkio_get_info, \ .bdrv_attach_aio_context = blkio_attach_aio_context, \ .bdrv_detach_aio_context = blkio_detach_aio_context, \
Some libblkio drivers may be able to work with regular files (e.g., io_uring) or otherwise resizable devices. Conservatively set BlockDriver::has_variable_length to true to ensure bdrv_nb_sectors() always gives up-to-date results. Also implement BlockDriver::bdrv_co_truncate for the case where no preallocation is needed and the device already has a size compatible with what was requested. Signed-off-by: Alberto Faria <afaria@redhat.com> --- This is based on Stefan's block tree: https://gitlab.com/stefanha/qemu/-/commits/block block/blkio.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)