Re: [PATCH 1/3] NFSv42: Fix pagecache invalidation after COPY/CLONE

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2021-11-16 at 08:49 -0500, Benjamin Coddington wrote:
> The mechanism in use to allow the client to see the results of
> COPY/CLONE
> is to drop those pages from the pagecache.  This forces the client to
> read
> those pages once more from the server.  However,
> truncate_pagecache_range()
> zeros out partial pages instead of dropping them.  Let us instead use
> invalidate_inode_pages2_range() with full-page offsets to ensure the
> client
> properly sees the results of COPY/CLONE operations.
> 
> Cc: <stable@vger.kernel.org> # v4.7+
> Fixes: 2e72448b07dc ("NFS: Add COPY nfs operation")
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---
>  fs/nfs/nfs42proc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> index a24349512ffe..bbcd4c80c5a6 100644
> --- a/fs/nfs/nfs42proc.c
> +++ b/fs/nfs/nfs42proc.c
> @@ -285,7 +285,10 @@ static void nfs42_copy_dest_done(struct inode
> *inode, loff_t pos, loff_t len)
>         loff_t newsize = pos + len;
>         loff_t end = newsize - 1;
>  
> -       truncate_pagecache_range(inode, pos, end);
> +       int error = invalidate_inode_pages2_range(inode->i_mapping,
> +                               pos >> PAGE_SHIFT, end >>
> PAGE_SHIFT);

Shouldn't that be "(end + PAGE_SIZE - 1) >> PAGE_SHIFT" in order to
align to the set of pages that fully contains the byte range from pos
to end?

> +       WARN_ON_ONCE(error);
> +
>         spin_lock(&inode->i_lock);
>         if (newsize > i_size_read(inode))
>                 i_size_write(inode, newsize);

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com