Re: [PATCH 2/2] NFSD: Fix last write offset handling in layoutcommit

[Christoph Hellwig <hch@infradead.org>]

On Fri, Jul 04, 2025 at 02:49:05PM +0300, Sergey Bashirov wrote:
> The data type of loca_last_write_offset is newoffset4 and is switched
> on a boolean value, no_newoffset, that indicates if a previous write
> occurred or not. If no_newoffset is FALSE, an offset is not given.
> This means that client does not try to update the file size. Thus,
> server should not try to calculate new file size and check if it fits
> into the seg range.
> 
> Co-developed-by: Konstantin Evtushenko <koevtushenko@yandex.com>
> Signed-off-by: Konstantin Evtushenko <koevtushenko@yandex.com>
> Signed-off-by: Sergey Bashirov <sergeybashirov@gmail.com>
> ---
>  fs/nfsd/blocklayout.c |  2 +-
>  fs/nfsd/nfs4proc.c    | 16 ++++++++--------
>  2 files changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
> index 19078a043e85..ee6544bdc045 100644
> --- a/fs/nfsd/blocklayout.c
> +++ b/fs/nfsd/blocklayout.c
> @@ -118,7 +118,7 @@ nfsd4_block_commit_blocks(struct inode *inode, struct nfsd4_layoutcommit *lcp,
>  		struct iomap *iomaps, int nr_iomaps)
>  {
>  	struct timespec64 mtime = inode_get_mtime(inode);
> -	loff_t new_size = lcp->lc_last_wr + 1;
> +	loff_t new_size = (lcp->lc_newoffset) ? lcp->lc_last_wr + 1 : 0;
>  	struct iattr iattr = { .ia_valid = 0 };
>  	int error;

Please guard the entire new_size check below instead, i.e.

	if (lcp->lc_newoffset) {
		loff_t new_size = lcp->lc_last_wr + 1;

		if (new_size > i_size_read(inode)) {
			iattr.ia_valid |= ATTR_SIZE;
			iattr.ia_size = new_size;
		}
	}


> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 37bdb937a0ae..ff38be803d8b 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -2482,7 +2482,7 @@ nfsd4_layoutcommit(struct svc_rqst *rqstp,
>  	const struct nfsd4_layout_seg *seg = &lcp->lc_seg;
>  	struct svc_fh *current_fh = &cstate->current_fh;
>  	const struct nfsd4_layout_ops *ops;
> -	loff_t new_size = lcp->lc_last_wr + 1;
> +	loff_t new_size = (lcp->lc_newoffset) ? lcp->lc_last_wr + 1 : 0;

Same here.