linux-kernel - [PATCH 5.12 303/384] jffs2: Hook up splice

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Date:   Mon, 10 May 2021 12:21:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Stanley <joel@....id.au>,
        Christoph Hellwig <hch@....de>,
        Lei YU <yulei.sh@...edance.com>,
        Richard Weinberger <richard@....at>
Subject: [PATCH 5.12 303/384] jffs2: Hook up splice_write callback

From: Joel Stanley <joel@....id.au>

commit 42984af09afc414d540fcc8247f42894b0378a91 upstream.

overlayfs using jffs2 as the upper filesystem would fail in some cases
since moving to v5.10. The test case used was to run 'touch' on a file
that exists in the lower fs, causing the modification time to be
updated. It returns EINVAL when the bug is triggered.

A bisection showed this was introduced in v5.9-rc1, with commit
36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").
Reverting that commit restores the expected behaviour.

Some digging showed that this was due to jffs2 lacking an implementation
of splice_write. (For unknown reasons the warn_unsupported that should
trigger was not displaying any output).

Adding this patch resolved the issue and the test now passes.

Cc: stable@...r.kernel.org
Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Signed-off-by: Joel Stanley <joel@....id.au>
Reviewed-by: Christoph Hellwig <hch@....de>
Tested-by: Lei YU <yulei.sh@...edance.com>
Signed-off-by: Richard Weinberger <richard@....at>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/jffs2/file.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -57,6 +57,7 @@ const struct file_operations jffs2_file_
 	.mmap =		generic_file_readonly_mmap,
 	.fsync =	jffs2_fsync,
 	.splice_read =	generic_file_splice_read,
+	.splice_write = iter_file_splice_write,
 };

 /* jffs2_file_inode_operations */