[PATCH] FUSE: implement the check_flags operation

[Enke Chen <enkechen@xxxxxxxxx>]

This patch implement the "check_flags" operation that passes the flag
setting by fcntl() and ioctl(fd, FIONBIO, &on) to fuse-based applications.

This patch depends on the following:

    [PATCH] VFS: pass the flag setting by fcntl() to vfs

Signed-off-by: Enke Chen <enkechen@xxxxxxxxx>

Version: 4.6.0_rc6_next_20160505

 fs/fuse/file.c            |   43 +++++++++++++++++++++++++++++++++++++++++++
 fs/fuse/fuse_i.h          |    3 +++
 include/uapi/linux/fuse.h |   10 ++++++++++
 3 files changed, 56 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9154f86..b457a40 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3010,6 +3010,47 @@ out:
 	return err;
 }
 
+static int fuse_do_setfl(unsigned int flags, struct file *file)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
+	struct fuse_setfl_in inarg;
+	FUSE_ARGS(args);
+	int err;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	if (fc->no_setfl)
+		return 0;
+
+	inarg.fh = ff->fh;
+	inarg.flags = flags;
+	inarg.setting = 1;
+	args.in.h.opcode = FUSE_SETFL;
+	args.in.h.nodeid = get_node_id(inode);
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	err = fuse_simple_request(fc, &args);
+	if (err == -ENOSYS) {
+		fc->no_setfl = 1;
+		err = 0;
+	}
+
+	return err;
+}
+
+static int fuse_file_check_flags(unsigned int flags, struct file *file,
+				 int setting)
+{
+	if (!setting)
+		return 0;
+
+	return fuse_do_setfl(flags, file);
+}
+
 static const struct file_operations fuse_file_operations = {
 	.llseek		= fuse_file_llseek,
 	.read_iter	= fuse_file_read_iter,
@@ -3026,6 +3067,7 @@ static const struct file_operations fuse_file_operations = {
 	.compat_ioctl	= fuse_file_compat_ioctl,
 	.poll		= fuse_file_poll,
 	.fallocate	= fuse_file_fallocate,
+	.check_flags	= fuse_file_check_flags,
 };
 
 static const struct file_operations fuse_direct_io_file_operations = {
@@ -3044,6 +3086,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
 	.poll		= fuse_file_poll,
 	.fallocate	= fuse_file_fallocate,
 	/* no splice_read */
+	.check_flags	= fuse_file_check_flags,
 };
 
 static const struct address_space_operations fuse_file_aops  = {
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index eddbe02..70b4f8d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -617,6 +617,9 @@ struct fuse_conn {
 	/** Is lseek not implemented by fs? */
 	unsigned no_lseek:1;
 
+	/** Is setfl implemented by fs? */
+	unsigned no_setfl: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 5974fae..c068650 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -105,6 +105,9 @@
  *
  *  7.24
  *  - add FUSE_LSEEK for SEEK_HOLE and SEEK_DATA support
+ *
+ *  7.25
+ *  - add FUSE_SETFL
  */
 
 #ifndef _LINUX_FUSE_H
@@ -362,6 +365,7 @@ enum fuse_opcode {
 	FUSE_READDIRPLUS   = 44,
 	FUSE_RENAME2       = 45,
 	FUSE_LSEEK         = 46,
+	FUSE_SETFL         = 47,
 
 	/* CUSE specific operations */
 	CUSE_INIT          = 4096,
@@ -773,4 +777,10 @@ struct fuse_lseek_out {
 	uint64_t	offset;
 };
 
+struct fuse_setfl_in {
+	uint64_t	fh;
+	uint32_t	flags;
+	uint32_t	setting;
+};
+
 #endif /* _LINUX_FUSE_H */
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