[PATCH 2/6] fuse: Create helper function if DIO write needs exclusive lock

[Bernd Schubert <bschubert@ddn.com>]

This is just a preparation to avoid code duplication in the next
commit.

Cc: Hao Xu <howeyxu@tencent.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Dharmendra Singh <dsingh@ddn.com>
Signed-off-by: Bernd Schubert <bschubert@ddn.com>
---
 fs/fuse/file.c | 48 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 33 insertions(+), 15 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index b1b9f2b9a37d..6b8b9512c336 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1298,6 +1298,37 @@ static ssize_t fuse_perform_write(struct kiocb *iocb, struct iov_iter *ii)
 	return res;
 }
 
+static bool fuse_io_past_eof(struct kiocb *iocb,
+					       struct iov_iter *iter)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
+}
+
+/*
+ * @return true if an exclusive lock direct IO writes is needed
+ */
+static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+
+	/* server side has to advise that it supports parallel dio writes */
+	if (!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES))
+		return false;
+
+	/* append will need to know the eventual eof - always needs a lock */
+	if (iocb->ki_flags & IOCB_APPEND)
+		return false;
+
+	/* parallel dio beyond eof is at least for now not supported */
+	if (fuse_io_past_eof(iocb, from))
+		return false;
+
+	return true;
+}
+
 static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
@@ -1557,25 +1588,12 @@ static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return res;
 }
 
-static bool fuse_direct_write_extending_i_size(struct kiocb *iocb,
-					       struct iov_iter *iter)
-{
-	struct inode *inode = file_inode(iocb->ki_filp);
-
-	return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
-}
-
 static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
-	struct file *file = iocb->ki_filp;
-	struct fuse_file *ff = file->private_data;
 	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
 	ssize_t res;
-	bool exclusive_lock =
-		!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES) ||
-		iocb->ki_flags & IOCB_APPEND ||
-		fuse_direct_write_extending_i_size(iocb, from);
+	bool exclusive_lock = fuse_dio_wr_exclusive_lock(iocb, from);
 
 	/*
 	 * Take exclusive lock if
@@ -1591,7 +1609,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		/* A race with truncate might have come up as the decision for
 		 * the lock type was done without holding the lock, check again.
 		 */
-		if (fuse_direct_write_extending_i_size(iocb, from)) {
+		if (fuse_io_past_eof(iocb, from)) {
 			inode_unlock_shared(inode);
 			inode_lock(inode);
 			exclusive_lock = true;
-- 
2.39.2