On Tue, 2020-11-03 at 10:55 -0500, Benjamin Coddington wrote:
> On 3 Nov 2020, at 10:33, trondmy@xxxxxxxxxx wrote:
>
> > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> >
> > If a readdir call returns more data than we can fit into one page
> > cache page, then allocate a new one for that data rather than
> > discarding the data.
> >
> > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > ---
> > fs/nfs/dir.c | 46 ++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 42 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> > index b4861a33ad60..788c2a2eeaa3 100644
> > --- a/fs/nfs/dir.c
> > +++ b/fs/nfs/dir.c
> > @@ -321,6 +321,26 @@ static void nfs_readdir_page_set_eof(struct
> > page
> > *page)
> > kunmap_atomic(array);
> > }
> >
> > +static void nfs_readdir_page_unlock_and_put(struct page *page)
> > +{
> > + unlock_page(page);
> > + put_page(page);
> > +}
> > +
> > +static struct page *nfs_readdir_page_get_next(struct address_space
> > *mapping,
> > + pgoff_t index, u64
> > cookie)
> > +{
> > + struct page *page;
> > +
> > + page = nfs_readdir_page_get_locked(mapping, index, cookie);
> > + if (page) {
> > + if (nfs_readdir_page_last_cookie(page) == cookie)
> > + return page;
> > + nfs_readdir_page_unlock_and_put(page);
> > + }
> > + return NULL;
> > +}
> > +
> > static inline
> > int is_32bit_api(void)
> > {
> > @@ -638,13 +658,15 @@ void nfs_prime_dcache(struct dentry *parent,
> > struct nfs_entry *entry,
> > }
> >
> > /* Perform conversion from xdr to cache array */
> > -static
> > -int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct
> > nfs_entry *entry,
> > - struct page **xdr_pages, struct
> > page *page, unsigned int buflen)
> > +static int nfs_readdir_page_filler(struct nfs_readdir_descriptor
> > *desc,
> > + struct nfs_entry *entry,
> > + struct page **xdr_pages,
> > + struct page *fillme, unsigned
> > int buflen)
> > {
> > + struct address_space *mapping = desc->file->f_mapping;
> > struct xdr_stream stream;
> > struct xdr_buf buf;
> > - struct page *scratch;
> > + struct page *scratch, *new, *page = fillme;
> > int status;
> >
> > scratch = alloc_page(GFP_KERNEL);
> > @@ -667,6 +689,19 @@ int
> > nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct
> > nfs_entry *en
> > desc->dir_verifier);
> >
> > status = nfs_readdir_add_to_array(entry, page);
> > + if (status != -ENOSPC)
> > + continue;
> > +
> > + if (page->mapping != mapping)
> > + break;
>
> ^^ How can this happen?
>
We call the same routines from uncached_readdir(), so the above is
really there in order to exit when we see those anonymous pages.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
