[2/2] NFS: rename nfs_direct_IO and use as ->swap_rw

Commit Message

NeilBrown April 29, 2022, 12:43 a.m. UTC

The nfs_direct_IO() exists to support SWAP IO, but hasn't worked for a
while.  We now need a ->swap_rw function which behaves slightly
differently, returning zero for success rather than a byte count.

So modify nfs_direct_IO accordingly, rename it, and use it as the
->swap_rw function.

Tested-by: Geert Uytterhoeven <[e-mail]> (on Renesas RSK+RZA1 with 32 MiB of SDRAM)
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: NeilBrown <[e-mail]>
---
 fs/nfs/direct.c        |   23 ++++++++++-------------
 fs/nfs/file.c          |    5 +----
 include/linux/nfs_fs.h |    2 +-
 3 files changed, 12 insertions(+), 18 deletions(-)

Comments

Andrew Morton April 29, 2022, 1:23 a.m. UTC | #1

On Fri, 29 Apr 2022 10:43:34 +1000 NeilBrown <[e-mail]> wrote:

> The nfs_direct_IO() exists to support SWAP IO, but hasn't worked for a
> while.  We now need a ->swap_rw function which behaves slightly
> differently, returning zero for success rather than a byte count.
> 
> So modify nfs_direct_IO accordingly, rename it, and use it as the
> ->swap_rw function.
> 

This one I insertion sorted into the series after
mm-introduce-swap_rw-and-use-it-for-reads-from-swp_fs_ops-swap-space.patch.
I can later fold this patch into that one of you think that's a better
presentation?

NeilBrown April 29, 2022, 2:05 a.m. UTC | #2

On Fri, 29 Apr 2022, Andrew Morton wrote:
> On Fri, 29 Apr 2022 10:43:34 +1000 NeilBrown <[e-mail]> wrote:
> 
> > The nfs_direct_IO() exists to support SWAP IO, but hasn't worked for a
> > while.  We now need a ->swap_rw function which behaves slightly
> > differently, returning zero for success rather than a byte count.
> > 
> > So modify nfs_direct_IO accordingly, rename it, and use it as the
> > ->swap_rw function.
> > 
> 
> This one I insertion sorted into the series after
> mm-introduce-swap_rw-and-use-it-for-reads-from-swp_fs_ops-swap-space.patch.
> I can later fold this patch into that one of you think that's a better
> presentation?
> 

I'm happy for the patches to remain separate - though adjacent is good.
If they were to be merged we'd need to fix up the commit message.
At least delete:

   Future patches will restore swap-over-NFS functionality.

Thanks,
NeilBrown

Patch

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 11c566d8769f..4eb2a8380a28 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -153,28 +153,25 @@  nfs_direct_count_bytes(struct nfs_direct_req *dreq,
 }
 
 /**
- * nfs_direct_IO - NFS address space operation for direct I/O
+ * nfs_swap_rw - NFS address space operation for swap I/O
  * @iocb: target I/O control block
  * @iter: I/O buffer
  *
- * The presence of this routine in the address space ops vector means
- * the NFS client supports direct I/O. However, for most direct IO, we
- * shunt off direct read and write requests before the VFS gets them,
- * so this method is only ever called for swap.
+ * Perform IO to the swap-file.  This is much like direct IO.
  */
-ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter)
 {
-	struct inode *inode = iocb->ki_filp->f_mapping->host;
-
-	/* we only support swap file calling nfs_direct_IO */
-	if (!IS_SWAPFILE(inode))
-		return 0;
+	ssize_t ret;
 
 	VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
 
 	if (iov_iter_rw(iter) == READ)
-		return nfs_file_direct_read(iocb, iter, true);
-	return nfs_file_direct_write(iocb, iter, true);
+		ret = nfs_file_direct_read(iocb, iter, true);
+	else
+		ret = nfs_file_direct_write(iocb, iter, true);
+	if (ret < 0)
+		return ret;
+	return 0;
 }
 
 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index e1d10a3e086a..bfb4b707b07e 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -490,10 +490,6 @@  static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 	struct rpc_clnt *clnt = NFS_CLIENT(inode);
 	struct nfs_client *cl = NFS_SERVER(inode)->nfs_client;
 
-	if (!file->f_mapping->a_ops->swap_rw)
-		/* Cannot support swap */
-		return -EINVAL;
-
 	spin_lock(&inode->i_lock);
 	blocks = inode->i_blocks;
 	isize = inode->i_size;
@@ -550,6 +546,7 @@  const struct address_space_operations nfs_file_aops = {
 	.error_remove_page = generic_error_remove_page,
 	.swap_activate = nfs_swap_activate,
 	.swap_deactivate = nfs_swap_deactivate,
+	.swap_rw = nfs_swap_rw,
 };
 
 /*
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b48b9259e02c..fd5543486a3f 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -507,7 +507,7 @@  static inline const struct cred *nfs_file_cred(struct file *file)
 /*
  * linux/fs/nfs/direct.c
  */
-extern ssize_t nfs_direct_IO(struct kiocb *, struct iov_iter *);
+int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter);
 ssize_t nfs_file_direct_read(struct kiocb *iocb,
 			     struct iov_iter *iter, bool swap);
 ssize_t nfs_file_direct_write(struct kiocb *iocb,