linux-kernel - Re: [PATCH v3 08/12] nfs: drop usage of folio_file

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Date: Mon, 29 Apr 2024 20:21:17 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	"Huang, Ying" <ying.huang@...el.com>, Chris Li <chrisl@...nel.org>,
	Barry Song <v-songbaohua@...o.com>,
	Ryan Roberts <ryan.roberts@....com>, Neil Brown <neilb@...e.de>,
	Minchan Kim <minchan@...nel.org>, Hugh Dickins <hughd@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Yosry Ahmed <yosryahmed@...gle.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 08/12] nfs: drop usage of folio_file_pos

On Tue, Apr 30, 2024 at 03:11:34AM +0800, Kairui Song wrote:
> +++ b/fs/nfs/file.c
> @@ -588,7 +588,7 @@ static vm_fault_t nfs_vm_page_mkwrite(struct vm_fault *vmf)
>  
>  	dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%pD2(%lu), offset %lld)\n",
>  		 filp, filp->f_mapping->host->i_ino,
> -		 (long long)folio_file_pos(folio));
> +		 (long long)folio_pos(folio));

Yes, we can't call page_mkwrite() on a swapcache page.

> +++ b/fs/nfs/nfstrace.h
> @@ -960,7 +960,7 @@ DECLARE_EVENT_CLASS(nfs_folio_event,
>  			__entry->fileid = nfsi->fileid;
>  			__entry->fhandle = nfs_fhandle_hash(&nfsi->fh);
>  			__entry->version = inode_peek_iversion_raw(inode);
> -			__entry->offset = folio_file_pos(folio);
> +			__entry->offset = folio_pos(folio);
>  			__entry->count = nfs_folio_length(folio);
>  		),
>  
> @@ -1008,7 +1008,7 @@ DECLARE_EVENT_CLASS(nfs_folio_event_done,
>  			__entry->fileid = nfsi->fileid;
>  			__entry->fhandle = nfs_fhandle_hash(&nfsi->fh);
>  			__entry->version = inode_peek_iversion_raw(inode);
> -			__entry->offset = folio_file_pos(folio);
> +			__entry->offset = folio_pos(folio);

These two I don't know about.

> +++ b/fs/nfs/write.c
> @@ -281,7 +281,7 @@ static void nfs_grow_file(struct folio *folio, unsigned int offset,
>  	end_index = ((i_size - 1) >> folio_shift(folio)) << folio_order(folio);
>  	if (i_size > 0 && folio_index(folio) < end_index)
>  		goto out;
> -	end = folio_file_pos(folio) + (loff_t)offset + (loff_t)count;
> +	end = folio_pos(folio) + (loff_t)offset + (loff_t)count;

This one concerns me.  Are we sure we can't call nfs_grow_file()
for a swapfile?

> @@ -2073,7 +2073,7 @@ int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio)
>   */
>  int nfs_wb_folio(struct inode *inode, struct folio *folio)
>  {
> -	loff_t range_start = folio_file_pos(folio);
> +	loff_t range_start = folio_pos(folio);
>  	loff_t range_end = range_start + (loff_t)folio_size(folio) - 1;

Likewise here.  Are we absolutely certain that swap I/O can't call this
function?