linux-kernel - [PATCH v2 6/7] NFS: direct-io: convert to FOLL

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Date:   Tue, 30 Aug 2022 21:18:42 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Jens Axboe <axboe@...nel.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Christoph Hellwig <hch@...radead.org>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>, Jan Kara <jack@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        <linux-block@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-xfs@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
        <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v2 6/7] NFS: direct-io: convert to FOLL_PIN pages

Convert the NFS Direct IO layer to use pin_user_pages_fast() and
unpin_user_page(), instead of get_user_pages_fast() and put_page().

The user of pin_user_pages_fast() depends upon:

1) CONFIG_BLK_USE_PIN_USER_PAGES_FOR_DIO, and

2) User-space-backed pages: user_backed_iter(i) == true

Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
 fs/nfs/direct.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 1707f46b1335..71b794f39ee2 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -142,11 +142,13 @@ int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter)
 	return 0;
 }
 
-static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
+static void nfs_direct_release_pages(struct iov_iter *iter, struct page **pages,
+				     unsigned int npages)
 {
-	unsigned int i;
-	for (i = 0; i < npages; i++)
-		put_page(pages[i]);
+	if (user_backed_iter(iter) || iov_iter_is_bvec(iter))
+		dio_w_unpin_user_pages(pages, npages);
+	else
+		release_pages(pages, npages);
 }
 
 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
@@ -332,11 +334,11 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 		size_t pgbase;
 		unsigned npages, i;
 
-		result = iov_iter_get_pages_alloc2(iter, &pagevec,
+		result = dio_w_iov_iter_pin_pages_alloc(iter, &pagevec,
 						  rsize, &pgbase);
 		if (result < 0)
 			break;
-	
+
 		bytes = result;
 		npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
 		for (i = 0; i < npages; i++) {
@@ -362,7 +364,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 			pos += req_len;
 			dreq->bytes_left -= req_len;
 		}
-		nfs_direct_release_pages(pagevec, npages);
+		nfs_direct_release_pages(iter, pagevec, npages);
 		kvfree(pagevec);
 		if (result < 0)
 			break;
@@ -791,8 +793,8 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 		size_t pgbase;
 		unsigned npages, i;
 
-		result = iov_iter_get_pages_alloc2(iter, &pagevec,
-						  wsize, &pgbase);
+		result = dio_w_iov_iter_pin_pages_alloc(iter, &pagevec,
+							wsize, &pgbase);
 		if (result < 0)
 			break;
 
@@ -829,7 +831,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 			pos += req_len;
 			dreq->bytes_left -= req_len;
 		}
-		nfs_direct_release_pages(pagevec, npages);
+		nfs_direct_release_pages(iter, pagevec, npages);
 		kvfree(pagevec);
 		if (result < 0)
 			break;
-- 
2.37.2