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Date:   Mon, 21 Nov 2022 18:15:21 -0800
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Message-ID: <20221122021536.1629178-7-drosen@google.com>
Subject: [RFC PATCH v2 06/21] fuse-bpf: Don't support export_operations
From:   Daniel Rosenberg <drosen@google.com>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     Amir Goldstein <amir73il@gmail.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org,
        bpf@vger.kernel.org, kernel-team@android.com,
        Daniel Rosenberg <drosen@google.com>
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Precedence: bulk

In the future, we may choose to support these, but it poses some
challenges. In order to create a disconnected dentry/inode, we'll need
to encode the mountpoint and bpf into the file_handle, which means we'd
need a stable representation of them. This also won't hold up to cases
where the bpf is not stateless. One possibility is registering bpf
programs and mounts in a specific order, so they can be assigned
consistent ids we can use in the file_handle. We can defer to the lower
filesystem for the lower inode's representation in the file_handle.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/fuse/inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 224d7dfe754d..bafb2832627d 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1100,6 +1100,14 @@ static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
 	nodeid = get_fuse_inode(inode)->nodeid;
 	generation = inode->i_generation;
 
+#ifdef CONFIG_FUSE_BPF
+	/* TODO: Does it make sense to support this in some cases? */
+	if (!nodeid && get_fuse_inode(inode)->backing_inode) {
+		*max_len = 0;
+		return FILEID_INVALID;
+	}
+#endif
+
 	fh[0] = (u32)(nodeid >> 32);
 	fh[1] = (u32)(nodeid & 0xffffffff);
 	fh[2] = generation;
-- 
2.38.1.584.g0f3c55d4c2-goog