Thus wrote Jeff Layton (jlayton@xxxxxxxxxx):
> On Sun, 2024-04-14 at 19:01 +0200, Martin Kaiser wrote:
> > With newer kernels that use fs_context for nfs mounts, remounts fail with
> > -EINVAL.
> > $ mount -t nfs -o nolock 10.0.0.1:/tmp/test /mnt/test/
> > $ mount -t nfs -o remount /mnt/test/
> > mount: mounting 10.0.0.1:/tmp/test on /mnt/test failed: Invalid argument
> > For remounts, the nfs server address and port are populated by
> > nfs_init_fs_context and later overwritten with 0x00 bytes by
> > nfs23_parse_monolithic. The remount then fails as the server address is
> > invalid.
> > Fix this by not overwriting nfs server info in nfs23_parse_monolithic if
> > we're doing a remount.
> > Fixes: f2aedb713c28 ("NFS: Add fs_context support.")
> > Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
> > ---
> > v3:
> > - rebased against linux-next from 12th April 2024
> > v2:
> > - rebased against linux-next from 26th February 2024
> > Dear all,
> > I'm resending this patch again. The problem that I'm trying to fix is still
> > present in linux-next. Thanks in advance for any reviews and comments.
> > I guess that we're taking this path for remounts
> > do_remount
> > fs_context_for_reconfigure
> > alloc_fs_context
> > init_fs_context == nfs_init_fs_context
> > fc->root is set for remounts
> > ctx->nfs_server is populated
> > parse_monolithic_mount_data
> > nfs_fs_context_parse_monolithic
> > nfs23_parse_monolithic
> > ctx->nfs_server is overwritten with data from mount request
> > An alternative to checking for !is_remount_fc(fc) would be to check
> > if (ctx->nfs_server.addrlen == 0)
> > fs/nfs/fs_context.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> > diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
> > index d0a0956f8a13..cac1157be2c2 100644
> > --- a/fs/nfs/fs_context.c
> > +++ b/fs/nfs/fs_context.c
> > @@ -1112,9 +1112,12 @@ static int nfs23_parse_monolithic(struct fs_context *fc,
> > ctx->acdirmax = data->acdirmax;
> > ctx->need_mount = false;
> > - memcpy(sap, &data->addr, sizeof(data->addr));
> > - ctx->nfs_server.addrlen = sizeof(data->addr);
> > - ctx->nfs_server.port = ntohs(data->addr.sin_port);
> > + if (!is_remount_fc(fc)) {
> > + memcpy(sap, &data->addr, sizeof(data->addr));
> > + ctx->nfs_server.addrlen = sizeof(data->addr);
> > + ctx->nfs_server.port = ntohs(data->addr.sin_port);
> > + }
> > +
> > if (sap->ss_family != AF_INET ||
> > !nfs_verify_server_address(sap))
> > goto out_no_address;
> Doesn't nfs4_parse_monolithic need the same fix?
Sorry for the delayed response. It took me a moment to set up a test with nfs4
(busybox mount has no nfs4 support).
The nfs4 remounts do not fail for me. The mount syscall goes into
nfs4_parse_monolithic and
if (data->version != 1)
return generic_parse_monolithic(fc, data);
branches off into generic_parse_monolithic before the server address is
overwritten (this is what breaks nfs23).
Best regards,
Martin
