diff mbox series

[v2,05/16] NFS: Don't discard readdir results

Message ID 20201103153329.531942-6-trondmy@kernel.org (mailing list archive)
State New
Headers show
Series Readdir enhancements | expand

Commit Message

trondmy@kernel.org Nov. 3, 2020, 3:33 p.m. UTC
From: Trond Myklebust <trond.myklebust@hammerspace.com>

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@hammerspace.com>
---
 fs/nfs/dir.c | 46 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 42 insertions(+), 4 deletions(-)

Comments

Benjamin Coddington Nov. 3, 2020, 3:55 p.m. UTC | #1
On 3 Nov 2020, at 10:33, trondmy@kernel.org wrote:

> From: Trond Myklebust <trond.myklebust@hammerspace.com>
>
> 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@hammerspace.com>
> ---
>  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?

Ben
Trond Myklebust Nov. 3, 2020, 4:14 p.m. UTC | #2
On Tue, 2020-11-03 at 10:55 -0500, Benjamin Coddington wrote:
> On 3 Nov 2020, at 10:33, trondmy@kernel.org wrote:
> 
> > From: Trond Myklebust <trond.myklebust@hammerspace.com>
> > 
> > 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@hammerspace.com>
> > ---
> >  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.
diff mbox series

Patch

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;
+		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) {
@@ -682,6 +717,9 @@  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;
 }