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From:   Jidong Xiao <jidong.xiao@gmail.com>
Date:   Mon, 5 Dec 2022 10:47:14 -0700
Message-ID: <CAG4AFWaVZdDV=NkC-xcmP+kc2AhYHg26VOUKa8nKy03ptPiqgg@mail.gmail.com>
Subject: Re: Is Linux NFS block size 512 bytes or is this a bug?
To:     Benjamin Coddington <bcodding@redhat.com>
Cc:     linux-nfs@vger.kernel.org
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On Mon, Dec 5, 2022 at 10:38 AM Benjamin Coddington <bcodding@redhat.com> wrote:
>
> On 5 Dec 2022, at 0:44, Jidong Xiao wrote:
>
> > Hi,
> >
> > I saw this line in fs/nfsd/nfs3xdr.c:
> >
> > /* used */
> > p = xdr_encode_hyper(p, ((u64)stat->blocks) << 9);
> >
> > It seems we are left-shifting the blocks 9 bits, to get the number of
> > bytes used. Is this a bug or we know the block size is always 512
> > bytes?
>
> By calling vfs_getattr(), which needs to behave for stat(2) syscall as
> returning the number of 512 byte blocks.  I think we're stuck with the
> traditional idea that blocks are always 512 bytes in linux, at least from
> the perspective of stat().
>
> The history of such is beyond my time, but I don't think this is a bug.
>
> Ben
>

I see. Thank you!

-Jidong