Re: [PATCH 4/4] ceph: remove page_snap_context()

[Matthew Wilcox <willy@infradead.org>]

On Sun, Aug 02, 2026 at 12:50:05PM -0400, Tal Zussman wrote:
> Convert the final caller in get_writepages_data_length() to use a folio
> and ceph_folio_snap_context(), then remove page_snap_context().
> 
> This drops the last open-coded use of page->private in ceph's writeback
> path.

This one I'm deeply conflicted about.  It's adding an extra call to
compound_head() ... and we're not getting much for it.

I'd feel better about it if it started with::

 static u64 get_writepages_data_length(struct inode *inode,
                                       struct page *page, u64 start)
 {
+	struct folio *folio = page_folio(page);

and then we had a ceph_fscrypt_pagecache_folio() function and
ceph_fscrypt_folio_offset() (we already have a fscrypt_is_bounce_page())

That way we'd have this function entirely converted except for its
argument, and a future patch can do the conversion with little fuss.
And we'd get rid of one of the four remaining calls to
fscrypt_is_bounce_page()

> Signed-off-by: Tal Zussman <tz2294@columbia.edu>
> ---
>  fs/ceph/addr.c | 15 ++++-----------
>  1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index f4aaf9a5f196..702cf5fc1eab 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -29,9 +29,9 @@
>   *
>   * There are a few funny things going on here.
>   *
> - * The page->private field is used to reference a struct
> - * ceph_snap_context for _every_ dirty page.  This indicates which
> - * snapshot the page was logically dirtied in, and thus which snap
> + * The folio->private field is used to reference a struct
> + * ceph_snap_context for _every_ dirty folio.  This indicates which
> + * snapshot the folio was logically dirtied in, and thus which snap
>   * context needs to be associated with the osd write during writeback.
>   *
>   * Similarly, struct ceph_inode_info maintains a set of counters to
> @@ -68,13 +68,6 @@
>  static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
>  					struct folio **foliop, void **_fsdata);
>  
> -static inline struct ceph_snap_context *page_snap_context(struct page *page)
> -{
> -	if (PagePrivate(page))
> -		return (void *)page->private;
> -	return NULL;
> -}
> -
>  static inline struct ceph_snap_context *ceph_folio_snap_context(struct folio *folio)
>  {
>  	if (folio_test_private(folio))
> @@ -697,7 +690,7 @@ static u64 get_writepages_data_length(struct inode *inode,
>  	u64 end = i_size_read(inode);
>  	u64 ret;
>  
> -	snapc = page_snap_context(ceph_fscrypt_pagecache_page(page));
> +	snapc = ceph_folio_snap_context(page_folio(ceph_fscrypt_pagecache_page(page)));
>  	if (snapc != ci->i_head_snapc) {
>  		bool found = false;
>  		spin_lock(&ci->i_ceph_lock);
> 
> -- 
> 2.39.5
>