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From:   "Benjamin Coddington" <bcodding@redhat.com>
To:     trondmy@kernel.org
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH 03/12] NFS: Clean up nfs_readdir_page_filler()
Date:   Tue, 03 Nov 2020 09:18:53 -0500
Message-ID: <36E36AEF-E3D3-472B-A837-FF1312B7C169@redhat.com>
In-Reply-To: <20201102180658.6218-4-trondmy@kernel.org>
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 <20201102180658.6218-2-trondmy@kernel.org>
 <20201102180658.6218-3-trondmy@kernel.org>
 <20201102180658.6218-4-trondmy@kernel.org>
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On 2 Nov 2020, at 13:06, trondmy@kernel.org wrote:

> From: Trond Myklebust <trond.myklebust@hammerspace.com>
>
> Clean up handling of the case where there are no entries in the 
> readdir
> reply.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  fs/nfs/dir.c | 39 ++++++++++++++++++---------------------
>  1 file changed, 18 insertions(+), 21 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 604ebe015387..68acbde3f914 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -601,16 +601,12 @@ int 
> nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct 
> nfs_entry *en
>  	struct xdr_stream stream;
>  	struct xdr_buf buf;
>  	struct page *scratch;
> -	unsigned int count = 0;
>  	int status;
>
>  	scratch = alloc_page(GFP_KERNEL);
>  	if (scratch == NULL)
>  		return -ENOMEM;
>
> -	if (buflen == 0)
> -		goto out_nopages;
> -
>  	xdr_init_decode_pages(&stream, &buf, xdr_pages, buflen);
>  	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
>
> @@ -619,27 +615,27 @@ int 
> nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct 
> nfs_entry *en
>  			entry->label->len = NFS4_MAXLABELLEN;
>
>  		status = xdr_decode(desc, entry, &stream);
> -		if (status != 0) {
> -			if (status == -EAGAIN)
> -				status = 0;
> +		if (status != 0)
>  			break;
> -		}
> -
> -		count++;
>
>  		if (desc->plus)
>  			nfs_prime_dcache(file_dentry(desc->file), entry,
>  					desc->dir_verifier);
>
>  		status = nfs_readdir_add_to_array(entry, page);
> -		if (status != 0)
> -			break;
> -	} while (!entry->eof);
> +	} while (!status && !entry->eof);
>
> -out_nopages:
> -	if (count == 0 || (status == -EBADCOOKIE && entry->eof != 0)) {
> -		nfs_readdir_page_set_eof(page);
> +	switch (status) {
> +	case -EBADCOOKIE:
> +		if (entry->eof) {
> +			nfs_readdir_page_set_eof(page);
> +			status = 0;
> +		}
> +		break;
> +	case -ENOSPC:

If you return ENOSPC, then you don't need to use
nfs_readdir_array_is_full(array) below..

> +	case -EAGAIN:
>  		status = 0;
> +		break;
>  	}
>
>  	put_page(scratch);
> @@ -714,14 +710,15 @@ int 
> nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page 
> *page,
>
>  		if (status < 0)
>  			break;
> +
>  		pglen = status;
> -		status = nfs_readdir_page_filler(desc, &entry, pages, page, pglen);
> -		if (status < 0) {
> -			if (status == -ENOSPC)
> -				status = 0;
> +		if (pglen == 0) {
> +			nfs_readdir_page_set_eof(page);
>  			break;
>  		}
> -	} while (!nfs_readdir_array_is_full(array));
> +
> +		status = nfs_readdir_page_filler(desc, &entry, pages, page, pglen);
> +	} while (!status && !nfs_readdir_array_is_full(array));

^^ here.

I suppose nfs_readdir_array_is_full() is nice and clear.. I wonder if 
the
compiler would optimize it away.

Ben