On Wed, Jun 16, 2021 at 01:47:13PM +0000, Trond Myklebust wrote:
> On Wed, 2021-06-16 at 20:44 +0800, Gao Xiang wrote:
> > When testing fstests with ext4 over nfs 4.2, I found generic/486
> > failed. The root cause is that the length of its xattr value is
> > min(st_blksize * 3 / 4, XATTR_SIZE_MAX)
> >
> > which is 4096 * 3 / 4 = 3072 for underlayfs ext4 rather than
> > XATTR_SIZE_MAX = 65536 for nfs since the block size would be wsize
> > (=131072) if bsize is not specified.
> >
> > Let's use pnfs_blksize first instead of using wsize directly if
> > bsize isn't specified. And the testcase itself can pass now.
> >
> > Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > Cc: Anna Schumaker <anna.schumaker@xxxxxxxxxx>
> > Cc: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
> > ---
> > Considering bsize is not specified, we might use pnfs_blksize
> > directly first rather than wsize.
> >
> > fs/nfs/super.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> > index fe58525cfed4..5015edf0cd9a 100644
> > --- a/fs/nfs/super.c
> > +++ b/fs/nfs/super.c
> > @@ -1068,9 +1068,13 @@ static void nfs_fill_super(struct super_block
> > *sb, struct nfs_fs_context *ctx)
> > snprintf(sb->s_id, sizeof(sb->s_id),
> > "%u:%u", MAJOR(sb->s_dev), MINOR(sb->s_dev));
> >
> > - if (sb->s_blocksize == 0)
> > - sb->s_blocksize = nfs_block_bits(server->wsize,
> > + if (sb->s_blocksize == 0) {
> > + unsigned int blksize = server->pnfs_blksize ?
> > + server->pnfs_blksize : server->wsize;
>
> NACK. The pnfs block size is a layout driver-specific quantity, and
> should not be used to substitute for the server-advertised block size.
> It only applies to I/O _if_ the client is holding a layout for a
> specific file and is using pNFS to do I/O to that file.
Honestly, I'm not sure if it's ok as well.
>
> It has nothing to do with xattrs at all.
Yet my question is how to deal with generic/486, should we just skip
the case directly? I cannot find some proper way to get underlayfs
block size or real xattr value limit.
For now, generic/486 will return ENOSPC at
fsetxattr(fd, "user.world", value, 65536, XATTR_REPLACE);
when testing new nfs4.2 xattr support.
Thanks,
Gao Xiang
>
> > +
> > + sb->s_blocksize = nfs_block_bits(blksize,
> > &sb-
> > >s_blocksize_bits);
> > + }
> >
> > nfs_super_set_maxbytes(sb, server->maxfilesize);
> > server->has_sec_mnt_opts = ctx->has_sec_mnt_opts;
>
> --
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@xxxxxxxxxxxxxxx
>
>
