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.
Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Signed-off-by: Joel Stanley <j...@jms.id.au>
---
fs/jffs2/file.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index f8fb89b10227..4fc8cd698d1a 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -57,6 +57,7 @@ const struct file_operations jffs2_file_operations =
.mmap = generic_file_readonly_mmap,
.fsync = jffs2_fsync,
.splice_read = generic_file_splice_read,
+ .splice_write = iter_file_splice_write,
};
/* jffs2_file_inode_operations */
--
2.30.2
