Re: [PATCH v6 1/2] io: Add support for MSG_PEEK for socket channel

[Daniel P . Berrangé]

On Thu, Feb 02, 2023 at 01:22:12PM +0100, Juan Quintela wrote:
> "manish.mishra" <manish.mishra@nutanix.com> wrote:
> > MSG_PEEK peeks at the channel, The data is treated as unread and
> > the next read shall still return this data. This support is
> > currently added only for socket class. Extra parameter 'flags'
> > is added to io_readv calls to pass extra read flags like MSG_PEEK.
> >
> > Reviewed-by: Peter Xu <peterx@redhat.com>
> > Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
> > Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> > Signed-off-by: manish.mishra <manish.mishra@nutanix.com>
> 
> 
> This change breaks RDMA migration.
> 
> FAILED: libcommon.fa.p/migration_rdma.c.o
> cc -m64 -mcx16 -Ilibcommon.fa.p -I/usr/include/pixman-1 
> -I/usr/include/libpng16 -I/usr/include/spice-server -I/usr/include/spice-1 
> -I/usr/include/cacard -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include 
> -I/usr/include/sysprof-4 -I/usr/include/nss3 -I/usr/include/nspr4 
> -I/usr/include/PCSC -I/usr/include/p11-kit-1 -I/usr/include/libusb-1.0 
> -I/usr/include/SDL2 -I/usr/include/libmount -I/usr/include/blkid 
> -I/usr/include/gio-unix-2.0 -I/usr/include/slirp -fdiagnostics-color=auto 
> -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g -isystem 
> /mnt/code/qemu/full/linux-headers -isystem linux-headers -iquote . -iquote 
> /mnt/code/qemu/full -iquote /mnt/code/qemu/full/include -iquote 
> /mnt/code/qemu/full/tcg/i386 -pthread -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 
> -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing 
> -fno-common -fwrapv -Wundef -Wwrite-strings -Wmissing-prototypes 
> -Wstrict-prototypes -Wredundant-decls -Wold-style-declaration 
> -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k 
> -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels 
> -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wmissing-format-attribute 
> -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi 
> -fstack-protector-strong -fPIE -D_REENTRANT -Wno-undef -DSTRUCT_IOVEC_DEFINED 
> -MD -MQ libcommon.fa.p/migration_rdma.c.o -MF 
> libcommon.fa.p/migration_rdma.c.o.d -o libcommon.fa.p/migration_rdma.c.o -c 
> ../../../../mnt/code/qemu/full/migration/rdma.c
> ../../../../mnt/code/qemu/full/migration/rdma.c: In function 
> ‘qio_channel_rdma_class_init’:
> ../../../../mnt/code/qemu/full/migration/rdma.c:4020:25: error: assignment to 
> ‘ssize_t (*)(QIOChannel *, const struct iovec *, size_t,  int **, size_t *, 
> int,  Error **)’ {aka ‘long int (*)(QIOChannel *, const struct iovec *, long 
> unsigned int,  int **, long unsigned int *, int,  Error **)’} from 
> incompatible pointer type ‘ssize_t (*)(QIOChannel *, const struct iovec *, 
> size_t,  int **, size_t *, Error **)’ {aka ‘long int (*)(QIOChannel *, const 
> struct iovec *, long unsigned int,  int **, long unsigned int *, Error **)’} 
> [-Werror=incompatible-pointer-types]
>  4020 |     ioc_klass->io_readv = qio_channel_rdma_readv;
>       |                         ^
> cc1: all warnings being treated as errors
> 
> And I don't really know how to fix it, because the problem is that rdma
> don't use qio_channel_readv_full() at all.

Likely qio_channel_rdma_readv just adds the 'int flags' param added.
It doesn't need to actually do anything with the flags as they are
checked before

With regards,
Daniel
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