From: NeilBrown <neilb@suse.de>
Date: Tue, 26 Oct 2021 14:19:08 +1100
Subject: [PATCH] NFS: move generic_write_checks() call from
 nfs_file_direct_write() to nfs_file_write()
Patch-mainline: Not yet - undergoing review
References: bsc#1191876

generic_write_checks() is not needed for swap-out writes, and fails if
they are attempted.
nfs_file_direct_write() currently calls generic_write_checks() and is in
turn called from:
  nfs_direct_IO  - only for swap-out
  nfs_file_write - for normal O_DIRECT write

So move the generic_write_checks() call into nfs_file_write().  This
allows NFS swap-out writes to complete.

Fixes: dc617f29dbe5 ("vfs: don't allow writes to swap files")
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/direct.c |    5 +----
 fs/nfs/file.c   |    6 +++++-
 2 files changed, 6 insertions(+), 5 deletions(-)

--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -905,10 +905,7 @@ ssize_t nfs_file_direct_write(struct kio
 	dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
 		file, iov_iter_count(iter), (long long) iocb->ki_pos);
 
-	result = generic_write_checks(iocb, iter);
-	if (result <= 0)
-		return result;
-	count = result;
+	count = iov_iter_count(iter);
 	nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 
 	pos = iocb->ki_pos;
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -626,8 +626,12 @@ ssize_t nfs_file_write(struct kiocb *ioc
 	if (result)
 		return result;
 
-	if (iocb->ki_flags & IOCB_DIRECT)
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		result = generic_write_checks(iocb, from);
+		if (result <= 0)
+			return result;
 		return nfs_file_direct_write(iocb, from);
+	}
 
 	dprintk("NFS: write(%pD2, %zu@%Ld)\n",
 		file, iov_iter_count(from), (long long) iocb->ki_pos);