On Thu, Oct 13, 2022 at 10:16:57AM +0200, Miklos Szeredi wrote:
> Willy,
>
> delete_from_page_cache() exporting was just removed, and seems like it's
> deprecated in favor of the folio functions. Should this code use the folio
> one and export that? Is the code even correct to begin with?
In general, all filesystem code should be converted from pages to folios.
Whether you want to support multi-page folios is up to you; a little
more complexity but a performance win.
I'm not thrilled about exporting filemap_remove_folio() or
delete_from_page_cache(). At the very least, please make it _GPL.
What's the harm in leaving an extra page in the page cache, as long
as it's initialised?
> Thanks,
> Miklos
>
> fs/fuse/readdir.c | 18 ++++++++++--------
> mm/folio-compat.c | 1 +
> 2 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
> index b4e565711045..4284e28be2e8 100644
> --- a/fs/fuse/readdir.c
> +++ b/fs/fuse/readdir.c
> @@ -65,25 +65,27 @@ static void fuse_add_dirent_to_cache(struct file *file,
> page = find_lock_page(file->f_mapping, index);
> } else {
> page = find_or_create_page(file->f_mapping, index,
> - mapping_gfp_mask(file->f_mapping));
> + mapping_gfp_mask(file->f_mapping) | __GFP_ZERO);
> }
> if (!page)
> return;
>
> spin_lock(&fi->rdc.lock);
> + addr = kmap_local_page(page);
> /* Raced with another readdir */
> if (fi->rdc.version != version || fi->rdc.size != size ||
> - WARN_ON(fi->rdc.pos != pos))
> - goto unlock;
> + WARN_ON(fi->rdc.pos != pos)) {
> + /* Was this page just created? */
> + if (!offset && !((struct fuse_dirent *) addr)->namelen)
> + delete_from_page_cache(page);
> + goto unmap;
> + }
>
> - addr = kmap_local_page(page);
> - if (!offset)
> - clear_page(addr);
> memcpy(addr + offset, dirent, reclen);
> - kunmap_local(addr);
> fi->rdc.size = (index << PAGE_SHIFT) + offset + reclen;
> fi->rdc.pos = dirent->off;
> -unlock:
> +unmap:
> + kunmap_local(addr);
> spin_unlock(&fi->rdc.lock);
> unlock_page(page);
> put_page(page);
> diff --git a/mm/folio-compat.c b/mm/folio-compat.c
> index e1e23b4947d7..83aaffa6d701 100644
> --- a/mm/folio-compat.c
> +++ b/mm/folio-compat.c
> @@ -128,6 +128,7 @@ void delete_from_page_cache(struct page *page)
> {
> return filemap_remove_folio(page_folio(page));
> }
> +EXPORT_SYMBOL(delete_from_page_cache);
>
> int try_to_release_page(struct page *page, gfp_t gfp)
> {
> --
> 2.37.3
>
