new iov_iter flavour - ITER_UBUF

Equivalent of single-segment iovec.  Initialized by iov_iter_ubuf(),
checked for by iter_is_ubuf(), otherwise behaves like ITER_IOVEC
ones.

We are going to expose the things like ->write_iter() et.al. to those
in subsequent commits.

New predicate (user_backed_iter()) that is true for ITER_IOVEC and
ITER_UBUF; places like direct-IO handling should use that for
checking that pages we modify after getting them from iov_iter_get_pages()
would need to be dirtied.

DO NOT assume that replacing iter_is_iovec() with user_backed_iter()
will solve all problems - there's code that uses iter_is_iovec() to
decide how to poke around in iov_iter guts and for that the predicate
replacement obviously won't suffice.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

8 files changed, 9 insertions, 9 deletions

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index da59e836a06e..c535de5852bf 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1262,7 +1262,7 @@ ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter,
 	size_t count = iov_iter_count(iter);
 	loff_t pos = iocb->ki_pos;
 	bool write = iov_iter_rw(iter) == WRITE;
-	bool should_dirty = !write && iter_is_iovec(iter);
+	bool should_dirty = !write && user_backed_iter(iter);
 
 	if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
 		return -EROFS;
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e64cda7a7610..e1e05b253daa 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4004,7 +4004,7 @@ static ssize_t __cifs_readv(
 	if (!is_sync_kiocb(iocb))
 		ctx->iocb = iocb;
 
-	if (iter_is_iovec(to))
+	if (user_backed_iter(to))
 		ctx->should_dirty = true;
 
 	if (direct) {
diff --git a/fs/direct-io.c b/fs/direct-io.c
index df5e2d048799..c7fc01c2d509 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1251,7 +1251,7 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	spin_lock_init(&dio->bio_lock);
 	dio->refcount = 1;
 
-	dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
+	dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ;
 	sdio.iter = iter;
 	sdio.final_block_in_request = end >> blkbits;
 
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 0e537e580dc1..8d657c2cd6f7 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1356,7 +1356,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
 	if (!fud)
 		return -EPERM;
 
-	if (!iter_is_iovec(to))
+	if (!user_backed_iter(to))
 		return -EINVAL;
 
 	fuse_copy_init(&cs, 1, to);
@@ -1949,7 +1949,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
 	if (!fud)
 		return -EPERM;
 
-	if (!iter_is_iovec(from))
+	if (!user_backed_iter(from))
 		return -EINVAL;
 
 	fuse_copy_init(&cs, 0, from);
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 00fa861aeead..c982e3afe3b4 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1465,7 +1465,7 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 			inode_unlock(inode);
 	}
 
-	io->should_dirty = !write && iter_is_iovec(iter);
+	io->should_dirty = !write && user_backed_iter(iter);
 	while (count) {
 		ssize_t nres;
 		fl_owner_t owner = current->files;
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 2cceb193dcd8..48e6cc74fdc1 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -780,7 +780,7 @@ static inline bool should_fault_in_pages(struct iov_iter *i,
 
 	if (!count)
 		return false;
-	if (!iter_is_iovec(i))
+	if (!user_backed_iter(i))
 		return false;
 
 	size = PAGE_SIZE;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index c75d33d5c3ce..4eb559a16c9e 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -533,7 +533,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 			iomi.flags |= IOMAP_NOWAIT;
 		}
 
-		if (iter_is_iovec(iter))
+		if (user_backed_iter(iter))
 			dio->flags |= IOMAP_DIO_DIRTY;
 	} else {
 		iomi.flags |= IOMAP_WRITE;
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 4eb2a8380a28..022e1ce63e62 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -478,7 +478,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
 	if (!is_sync_kiocb(iocb))
 		dreq->iocb = iocb;
 
-	if (iter_is_iovec(iter))
+	if (user_backed_iter(iter))
 		dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
 
 	if (!swap)