On Wed, Nov 4, 2020 at 11:27 AM <trondmy@xxxxxxxxx> 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 842f69120a01..f7248145c333 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -320,6 +320,26 @@ 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)
> {
> @@ -637,13 +657,15 @@ 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);
> @@ -666,6 +688,19 @@ 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;
> + new = nfs_readdir_page_get_next(mapping, page->index + 1,
> + entry->prev_cookie);
> + if (!new)
> + break;
> + if (page != fillme)
> + nfs_readdir_page_unlock_and_put(page);
> + page = new;
> + status = nfs_readdir_add_to_array(entry, page);
> } while (!status && !entry->eof);
>
> switch (status) {
> @@ -681,6 +716,9 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *en
> break;
> }
>
> + if (page != fillme)
> + nfs_readdir_page_unlock_and_put(page);
> +
> put_page(scratch);
> return status;
> }
> --
> 2.28.0
>
It doesn't look like this handles uncached_readdir. Were you planning
on addressing that somehow, or should we think about something like
this to move dtsize up as a parameter to nfs_readdir_xdr_to_array(),
and force uncached_readdir() to 1 page:
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index b6c3501e8f61..ca30e2dbb9c3 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -791,13 +791,12 @@ static struct page
**nfs_readdir_alloc_pages(size_t npages)
static int nfs_readdir_xdr_to_array(struct nfs_readdir_descriptor *desc,
struct page *page, __be32 *verf_arg,
- __be32 *verf_res)
+ __be32 *verf_res, size_t dtsize)
{
struct page **pages;
struct nfs_entry *entry;
size_t array_size;
struct inode *inode = file_inode(desc->file);
- size_t dtsize = NFS_SERVER(inode)->dtsize;
int status = -ENOMEM;
entry = kzalloc(sizeof(*entry), GFP_KERNEL);
@@ -879,13 +878,15 @@ static int find_and_lock_cache_page(struct
nfs_readdir_descriptor *desc)
struct nfs_inode *nfsi = NFS_I(inode);
__be32 verf[NFS_DIR_VERIFIER_SIZE];
int res;
+ size_t dtsize = NFS_SERVER(inode)->dtsize;
desc->page = nfs_readdir_page_get_cached(desc);
if (!desc->page)
return -ENOMEM;
if (nfs_readdir_page_needs_filling(desc->page)) {
res = nfs_readdir_xdr_to_array(desc, desc->page,
- nfsi->cookieverf, verf);
+ nfsi->cookieverf, verf,
+ dtsize);
if (res < 0) {
nfs_readdir_page_unlock_and_put_cached(desc);
if (res == -EBADCOOKIE || res == -ENOTSYNC) {
@@ -995,7 +996,8 @@ static int uncached_readdir(struct
nfs_readdir_descriptor *desc)
desc->duped = 0;
nfs_readdir_page_init_array(page, desc->dir_cookie);
- status = nfs_readdir_xdr_to_array(desc, page, desc->verf, verf);
+ status = nfs_readdir_xdr_to_array(desc, page, desc->verf, verf,
+ PAGE_SIZE);
if (status < 0)
goto out_release;
