On Wed, 2021-01-20 at 11:59 -0500, Benjamin Coddington wrote:
> Whenever we successfully locate our dir_cookie within the pagecache,
> or
> finish emitting entries to userspace, update the pagecache cursor.
> These
> updates provide marker points to validate pagecache pages in a future
> patch.
How isn't this going to end up subject to the exact same problem that
Dave Wysochanski's patchset had?
>
> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
> ---
> fs/nfs/dir.c | 29 +++++++++++++++++++++++++----
> 1 file changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 6626aff9f54d..7f6c84c8a412 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -150,6 +150,10 @@ struct nfs_cache_array {
> struct nfs_cache_array_entry array[];
> };
>
> +static const int cache_entries_per_page =
> + (PAGE_SIZE - sizeof(struct nfs_cache_array)) /
> + sizeof(struct nfs_cache_array_entry);
> +
> struct nfs_readdir_descriptor {
> struct file *file;
> struct page *page;
> @@ -251,6 +255,21 @@ static bool nfs_readdir_array_is_full(struct
> nfs_cache_array *array)
> return array->page_full;
> }
>
> +static void nfs_readdir_set_cursor(struct nfs_readdir_descriptor
> *desc, int index)
> +{
> + desc->pgc.entry_index = index;
> + desc->pgc.index_cookie = desc->dir_cookie;
> +}
> +
> +static void nfs_readdir_cursor_next(struct nfs_dir_page_cursor *pgc,
> u64 cookie)
> +{
> + pgc->index_cookie = cookie;
> + if (++pgc->entry_index == cache_entries_per_page) {
> + pgc->entry_index = 0;
> + pgc->page_index++;
> + }
> +}
> +
> /*
> * the caller is responsible for freeing qstr.name
> * when called by nfs_readdir_add_to_array, the strings will be
> freed in
> @@ -424,7 +443,7 @@ static int nfs_readdir_search_for_pos(struct
> nfs_cache_array *array,
>
> index = (unsigned int)diff;
> desc->dir_cookie = array->array[index].cookie;
> - desc->pgc.entry_index = index;
> + nfs_readdir_set_cursor(desc, index);
> return 0;
> out_eof:
> desc->eof = true;
> @@ -492,7 +511,7 @@ static int nfs_readdir_search_for_cookie(struct
> nfs_cache_array *array,
> else
> desc->ctx->pos = new_pos;
> desc->prev_index = new_pos;
> - desc->pgc.entry_index = i;
> + nfs_readdir_set_cursor(desc, i);
> return 0;
> }
> }
> @@ -519,9 +538,9 @@ static int nfs_readdir_search_array(struct
> nfs_readdir_descriptor *desc)
> status = nfs_readdir_search_for_cookie(array, desc);
>
> if (status == -EAGAIN) {
> - desc->pgc.index_cookie = array->last_cookie;
> + desc->pgc.entry_index = array->size - 1;
> + nfs_readdir_cursor_next(&desc->pgc, array-
> >last_cookie);
> desc->current_index += array->size;
> - desc->pgc.page_index++;
> }
> kunmap_atomic(array);
> return status;
> @@ -1035,6 +1054,8 @@ static void nfs_do_filldir(struct
> nfs_readdir_descriptor *desc)
> desc->eof = true;
>
> kunmap(desc->page);
> + desc->pgc.entry_index = i-1;
> + nfs_readdir_cursor_next(&desc->pgc, desc->dir_cookie);
> dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @
> cookie %llu\n",
> (unsigned long long)desc->dir_cookie);
> }
--
Trond Myklebust
CTO, Hammerspace Inc
4984 El Camino Real, Suite 208
Los Altos, CA 94022
www.hammer.space
