[PATCH v4] fuse: add support for copy_file_range()

[Niels de Vos <ndevos@redhat.com>]

There are several FUSE filesystems that can implement server-side copy
or other efficient copy/duplication/clone methods. The copy_file_range()
syscall is the standard interface that users have access to while not
depending on external libraries that bypass FUSE.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

---
libfuse: https://github.com/libfuse/libfuse/pull/259

v2: return ssize_t instead of long
v3: add nodeid_out to fuse_copy_file_range_in for libfuse expectations
v4: use fuse_write_out as response, correct write-back handling
---
 fs/fuse/file.c            |  80 +++++++++++++++++++++++++++++
 fs/fuse/fuse_i.h          |   3 ++
 include/uapi/linux/fuse.h | 104 +++++++++++++++++++++-----------------
 3 files changed, 142 insertions(+), 45 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a201fb0ac64f..6aea3675fd88 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3009,6 +3009,85 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 	return err;
 }
 
+static ssize_t fuse_copy_file_range(struct file *file_in, loff_t pos_in,
+				    struct file *file_out, loff_t pos_out,
+				    size_t len, unsigned int flags)
+{
+	struct fuse_file *ff_in = file_in->private_data;
+	struct fuse_file *ff_out = file_out->private_data;
+	struct inode *inode_out = file_inode(file_out);
+	struct fuse_inode *fi_out = get_fuse_inode(inode_out);
+	struct fuse_conn *fc = ff_in->fc;
+	FUSE_ARGS(args);
+	struct fuse_copy_file_range_in inarg = {
+		.fh_in = ff_in->fh,
+		.off_in = pos_in,
+		.nodeid_out = ff_out->nodeid,
+		.fh_out = ff_out->fh,
+		.off_out = pos_out,
+		.len = len,
+		.flags = flags
+	};
+	struct fuse_write_out outarg;
+	ssize_t err;
+	/* mark unstable when write-back is not used, and file_out gets
+	 * extended */
+	bool is_unstable = (!fc->writeback_cache) &&
+			   ((pos_out + len) > inode_out->i_size);
+
+	if (fc->no_copy_file_range)
+		return -EOPNOTSUPP;
+
+	inode_lock(inode_out);
+
+	if (fc->writeback_cache) {
+		err = filemap_write_and_wait_range(inode_out->i_mapping,
+						   pos_out, pos_out + len);
+		if (err)
+			goto out;
+
+		fuse_sync_writes(inode_out);
+	}
+
+	if (is_unstable)
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state);
+
+	args.in.h.opcode = FUSE_COPY_FILE_RANGE;
+	args.in.h.nodeid = ff_in->nodeid;
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	args.out.numargs = 1;
+	args.out.args[0].size = sizeof(outarg);
+	args.out.args[0].value = &outarg;
+	err = fuse_simple_request(fc, &args);
+	if (err == -ENOSYS) {
+		fc->no_copy_file_range = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (err)
+		goto out;
+
+	if (fc->writeback_cache) {
+		bool changed = fuse_write_update_size(inode_out,
+						      pos_out + outarg.size);
+
+		if (changed)
+			file_update_time(file_out);
+	}
+
+	fuse_invalidate_attr(inode_out);
+
+	err = outarg.size;
+out:
+	if (is_unstable)
+		clear_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state);
+
+	inode_unlock(inode_out);
+
+	return err;
+}
+
 static const struct file_operations fuse_file_operations = {
 	.llseek		= fuse_file_llseek,
 	.read_iter	= fuse_file_read_iter,
@@ -3025,6 +3104,7 @@ static const struct file_operations fuse_file_operations = {
 	.compat_ioctl	= fuse_file_compat_ioctl,
 	.poll		= fuse_file_poll,
 	.fallocate	= fuse_file_fallocate,
+	.copy_file_range = fuse_copy_file_range,
 };
 
 static const struct file_operations fuse_direct_io_file_operations = {
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5256ad333b05..ea848bb7d9e2 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -637,6 +637,9 @@ struct fuse_conn {
 	/** Allow other than the mounter user to access the filesystem ? */
 	unsigned allow_other:1;
 
+	/** Does the filesystem support copy_file_range? */
+	unsigned no_copy_file_range:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 92fa24c24c92..c806a17beaef 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -116,6 +116,9 @@
  *
  *  7.27
  *  - add FUSE_ABORT_ERROR
+ *
+ *  7.28
+ *  - add FUSE_COPY_FILE_RANGE
  */
 
 #ifndef _LINUX_FUSE_H
@@ -337,53 +340,54 @@ struct fuse_file_lock {
 #define FUSE_POLL_SCHEDULE_NOTIFY (1 << 0)
 
 enum fuse_opcode {
-	FUSE_LOOKUP	   = 1,
-	FUSE_FORGET	   = 2,  /* no reply */
-	FUSE_GETATTR	   = 3,
-	FUSE_SETATTR	   = 4,
-	FUSE_READLINK	   = 5,
-	FUSE_SYMLINK	   = 6,
-	FUSE_MKNOD	   = 8,
-	FUSE_MKDIR	   = 9,
-	FUSE_UNLINK	   = 10,
-	FUSE_RMDIR	   = 11,
-	FUSE_RENAME	   = 12,
-	FUSE_LINK	   = 13,
-	FUSE_OPEN	   = 14,
-	FUSE_READ	   = 15,
-	FUSE_WRITE	   = 16,
-	FUSE_STATFS	   = 17,
-	FUSE_RELEASE       = 18,
-	FUSE_FSYNC         = 20,
-	FUSE_SETXATTR      = 21,
-	FUSE_GETXATTR      = 22,
-	FUSE_LISTXATTR     = 23,
-	FUSE_REMOVEXATTR   = 24,
-	FUSE_FLUSH         = 25,
-	FUSE_INIT          = 26,
-	FUSE_OPENDIR       = 27,
-	FUSE_READDIR       = 28,
-	FUSE_RELEASEDIR    = 29,
-	FUSE_FSYNCDIR      = 30,
-	FUSE_GETLK         = 31,
-	FUSE_SETLK         = 32,
-	FUSE_SETLKW        = 33,
-	FUSE_ACCESS        = 34,
-	FUSE_CREATE        = 35,
-	FUSE_INTERRUPT     = 36,
-	FUSE_BMAP          = 37,
-	FUSE_DESTROY       = 38,
-	FUSE_IOCTL         = 39,
-	FUSE_POLL          = 40,
-	FUSE_NOTIFY_REPLY  = 41,
-	FUSE_BATCH_FORGET  = 42,
-	FUSE_FALLOCATE     = 43,
-	FUSE_READDIRPLUS   = 44,
-	FUSE_RENAME2       = 45,
-	FUSE_LSEEK         = 46,
+	FUSE_LOOKUP		= 1,
+	FUSE_FORGET		= 2,  /* no reply */
+	FUSE_GETATTR		= 3,
+	FUSE_SETATTR		= 4,
+	FUSE_READLINK		= 5,
+	FUSE_SYMLINK		= 6,
+	FUSE_MKNOD		= 8,
+	FUSE_MKDIR		= 9,
+	FUSE_UNLINK		= 10,
+	FUSE_RMDIR		= 11,
+	FUSE_RENAME		= 12,
+	FUSE_LINK		= 13,
+	FUSE_OPEN		= 14,
+	FUSE_READ		= 15,
+	FUSE_WRITE		= 16,
+	FUSE_STATFS		= 17,
+	FUSE_RELEASE		= 18,
+	FUSE_FSYNC		= 20,
+	FUSE_SETXATTR		= 21,
+	FUSE_GETXATTR		= 22,
+	FUSE_LISTXATTR		= 23,
+	FUSE_REMOVEXATTR	= 24,
+	FUSE_FLUSH		= 25,
+	FUSE_INIT		= 26,
+	FUSE_OPENDIR		= 27,
+	FUSE_READDIR		= 28,
+	FUSE_RELEASEDIR		= 29,
+	FUSE_FSYNCDIR		= 30,
+	FUSE_GETLK		= 31,
+	FUSE_SETLK		= 32,
+	FUSE_SETLKW		= 33,
+	FUSE_ACCESS		= 34,
+	FUSE_CREATE		= 35,
+	FUSE_INTERRUPT		= 36,
+	FUSE_BMAP		= 37,
+	FUSE_DESTROY		= 38,
+	FUSE_IOCTL		= 39,
+	FUSE_POLL		= 40,
+	FUSE_NOTIFY_REPLY	= 41,
+	FUSE_BATCH_FORGET	= 42,
+	FUSE_FALLOCATE		= 43,
+	FUSE_READDIRPLUS	= 44,
+	FUSE_RENAME2		= 45,
+	FUSE_LSEEK		= 46,
+	FUSE_COPY_FILE_RANGE	= 47,
 
 	/* CUSE specific operations */
-	CUSE_INIT          = 4096,
+	CUSE_INIT		= 4096,
 };
 
 enum fuse_notify_code {
@@ -792,4 +796,14 @@ struct fuse_lseek_out {
 	uint64_t	offset;
 };
 
+struct fuse_copy_file_range_in {
+	uint64_t	fh_in;
+	uint64_t	off_in;
+	uint64_t	nodeid_out;
+	uint64_t	fh_out;
+	uint64_t	off_out;
+	uint64_t	len;
+	uint64_t	flags;
+};
+
 #endif /* _LINUX_FUSE_H */
-- 
2.17.1