fuse: implement splice read/write passthrough

This allows passing fstests generic/249 and generic/591.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/file.c

@@ -1723,6 +1723,31 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		return fuse_cache_write_iter(iocb, from);
 }
 
+static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
+				struct pipe_inode_info *pipe, size_t len,
+				unsigned int flags)
+{
+	struct fuse_file *ff = in->private_data;
+
+	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
+	if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_passthrough_splice_read(in, ppos, pipe, len, flags);
+	else
+		return filemap_splice_read(in, ppos, pipe, len, flags);
+}
+
+static ssize_t fuse_splice_write(struct pipe_inode_info *pipe, struct file *out,
+				 loff_t *ppos, size_t len, unsigned int flags)
+{
+	struct fuse_file *ff = out->private_data;
+
+	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
+	if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);
+	else
+		return iter_file_splice_write(pipe, out, ppos, len, flags);
+}
+
 static void fuse_writepage_free(struct fuse_writepage_args *wpa)
 {
 	struct fuse_args_pages *ap = &wpa->ia.ap;
@@ -3303,8 +3328,8 @@ static const struct file_operations fuse_file_operations = {
 	.lock		= fuse_file_lock,
 	.get_unmapped_area = thp_get_unmapped_area,
 	.flock		= fuse_file_flock,
-	.splice_read	= filemap_splice_read,
-	.splice_write	= iter_file_splice_write,
+	.splice_read	= fuse_splice_read,
+	.splice_write	= fuse_splice_write,
 	.unlocked_ioctl	= fuse_file_ioctl,
 	.compat_ioctl	= fuse_file_compat_ioctl,
 	.poll		= fuse_file_poll,

fs/fuse/fuse_i.h

@@ -1468,5 +1468,11 @@ static inline struct file *fuse_file_passthrough(struct fuse_file *ff)
 
 ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter);
 ssize_t fuse_passthrough_write_iter(struct kiocb *iocb, struct iov_iter *iter);
+ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
+				     struct pipe_inode_info *pipe,
+				     size_t len, unsigned int flags);
+ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
+				      struct file *out, loff_t *ppos,
+				      size_t len, unsigned int flags);
 
 #endif /* _FS_FUSE_I_H */

fs/fuse/passthrough.c

@@ -9,6 +9,7 @@
 
 #include <linux/file.h>
 #include <linux/backing-file.h>
+#include <linux/splice.h>
 
 static void fuse_file_accessed(struct file *file)
 {
@@ -79,6 +80,50 @@ ssize_t fuse_passthrough_write_iter(struct kiocb *iocb,
 	return ret;
 }
 
+ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
+				     struct pipe_inode_info *pipe,
+				     size_t len, unsigned int flags)
+{
+	struct fuse_file *ff = in->private_data;
+	struct file *backing_file = fuse_file_passthrough(ff);
+	struct backing_file_ctx ctx = {
+		.cred = ff->cred,
+		.user_file = in,
+		.accessed = fuse_file_accessed,
+	};
+
+	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
+		 backing_file, ppos ? *ppos : 0, len, flags);
+
+	return backing_file_splice_read(backing_file, ppos, pipe, len, flags,
+					&ctx);
+}
+
+ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
+				      struct file *out, loff_t *ppos,
+				      size_t len, unsigned int flags)
+{
+	struct fuse_file *ff = out->private_data;
+	struct file *backing_file = fuse_file_passthrough(ff);
+	struct inode *inode = file_inode(out);
+	ssize_t ret;
+	struct backing_file_ctx ctx = {
+		.cred = ff->cred,
+		.user_file = out,
+		.end_write = fuse_file_modified,
+	};
+
+	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
+		 backing_file, ppos ? *ppos : 0, len, flags);
+
+	inode_lock(inode);
+	ret = backing_file_splice_write(pipe, backing_file, ppos, len, flags,
+					&ctx);
+	inode_unlock(inode);
+
+	return ret;
+}
+
 struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
 {
 	if (fb && refcount_inc_not_zero(&fb->count))