linux-kernel - [PATCH] fs: read_write: make default in vfs_copy_file

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Message-Id: <20231205001620.4566-1-spasswolf@web.de>
Date:   Tue,  5 Dec 2023 01:16:20 +0100
From:   Bert Karwatzki <spasswolf@....de>
To:     amir73il@...il.com, Jan Kara <jack@...e.cz>,
        Christian Brauner <brauner@...nel.org>
Cc:     axboe@...nel.dk, dhowells@...hat.com, hch@....de,
        jlayton@...nel.org, josef@...icpanda.com,
        linux-fsdevel@...r.kernel.org, miklos@...redi.hu,
        viro@...iv.linux.org.uk, Bert Karwatzki <spasswolf@....de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] fs: read_write: make default in vfs_copy_file_range() reachable

If vfs_copy_file_range() is called with (flags & COPY_FILE_SPLICE == 0)
and both file_out->f_op->copy_file_range and file_in->f_op->remap_file_range
are NULL, too, the default call to do_splice_direct() cannot be reached.
This patch adds an else clause to make the default reachable in all
cases.

Signed-off-by: Bert Karwatzki <spasswolf@....de>
---
 fs/read_write.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/read_write.c b/fs/read_write.c
index e0c2c1b5962b..3599c54bd26d 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1554,6 +1554,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 		/* fallback to splice */
 		if (ret <= 0)
 			splice = true;
+	} else {
+		splice = true;
 	}

 	file_end_write(file_out);
--
2.39.2

Since linux-next-20231204 I noticed that it was impossible to start the
game Path of Exile (using the steam client). I bisected the error to
commit 05ee2d85cd4ace5cd37dc24132e3fd7f5142ebef. Reverting this commit
in linux-next-20231204 made the game start again and after inserting
printks into vfs_copy_file_range() I found that steam (via python3)
calls this function with (flags & COPY_FILE_SPLICE == 0),
file_out->f_op->copy_file_range == NULL and
file_in->f_op->remap_file_range == NULL so the default is never reached.
This patch adds a catch all else clause so the default is reached in
all cases. This patch fixes the describe issue with steam and Path of
Exile.

Bert Karwatzki