[PATCH v1 08/17] fuse: add passthrough ops gating

[Joanne Koong <joannelkoong@gmail.com>]

Route existing callers through a passthrough ops mask check to verify
whether passthrough can be called for the operation or not. The check is
only done when FUSE_PASSTHROUGH_INO mode is enabled, which preserves
backwards compatibility with prior passthrough behavior.

It is safe to get the backing file by accessing ff->passthrough directly
in passthrough.c because passthrough.c is only compiled with
CONFIG_FUSE_PASSTHROUGH=y and the caller has already done the ops check.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 fs/fuse/file.c        | 14 ++++++++------
 fs/fuse/fuse_i.h      | 14 +++++++++++++-
 fs/fuse/passthrough.c | 12 ++++++------
 fs/fuse/readdir.c     |  2 +-
 4 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e719c54c12d2..a1de70bc589d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -324,7 +324,7 @@ static void fuse_prepare_release(struct fuse_inode *fi, struct fuse_file *ff,
 	struct fuse_conn *fc = ff->fm->fc;
 	struct fuse_release_args *ra = &ff->args->release_args;
 
-	if (fuse_file_passthrough(ff))
+	if (fuse_file_passthrough(&fi->inode, ff, 0))
 		fuse_passthrough_release(ff, fuse_inode_backing(fi));
 
 	/* Inode is NULL on error path of fuse_create_open() */
@@ -1838,7 +1838,7 @@ static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
 	if (ff->open_flags & FOPEN_DIRECT_IO)
 		return fuse_direct_read_iter(iocb, to);
-	else if (fuse_file_passthrough(ff))
+	else if (fuse_file_passthrough(inode, ff, FUSE_PASSTHROUGH_OP_READ))
 		return fuse_passthrough_read_iter(iocb, to);
 	else
 		return fuse_cache_read_iter(iocb, to);
@@ -1859,7 +1859,7 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
 	if (ff->open_flags & FOPEN_DIRECT_IO)
 		return fuse_direct_write_iter(iocb, from);
-	else if (fuse_file_passthrough(ff))
+	else if (fuse_file_passthrough(inode, ff, FUSE_PASSTHROUGH_OP_WRITE))
 		return fuse_passthrough_write_iter(iocb, from);
 	else
 		return fuse_cache_write_iter(iocb, from);
@@ -1872,7 +1872,8 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
 	struct fuse_file *ff = in->private_data;
 
 	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
-	if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
+	if (fuse_file_passthrough(file_inode(in), ff, FUSE_PASSTHROUGH_OP_READ) &&
+	    !(ff->open_flags & FOPEN_DIRECT_IO))
 		return fuse_passthrough_splice_read(in, ppos, pipe, len, flags);
 	else
 		return filemap_splice_read(in, ppos, pipe, len, flags);
@@ -1884,7 +1885,8 @@ static ssize_t fuse_splice_write(struct pipe_inode_info *pipe, struct file *out,
 	struct fuse_file *ff = out->private_data;
 
 	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
-	if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
+	if (fuse_file_passthrough(file_inode(out), ff, FUSE_PASSTHROUGH_OP_WRITE) &&
+	    !(ff->open_flags & FOPEN_DIRECT_IO))
 		return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);
 	else
 		return iter_file_splice_write(pipe, out, ppos, len, flags);
@@ -2397,7 +2399,7 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 	 * in passthrough mode, either mmap to backing file or fail mmap,
 	 * because mixing cached mmap and passthrough io mode is not allowed.
 	 */
-	if (fuse_file_passthrough(ff))
+	if (fuse_file_passthrough(inode, ff, FUSE_PASSTHROUGH_RW_OPS))
 		return fuse_passthrough_mmap(file, vma);
 	else if (fuse_inode_backing(get_fuse_inode(inode)))
 		return -ENODEV;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index a15fb508fd28..45d9184d0f7a 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1630,9 +1630,21 @@ static inline struct fuse_backing *fuse_inode_backing_set(struct fuse_inode *fi,
 struct fuse_backing *fuse_passthrough_open(struct file *file, int backing_id);
 void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb);
 
-static inline struct file *fuse_file_passthrough(struct fuse_file *ff)
+static inline struct file *fuse_file_passthrough(struct inode *inode,
+						 struct fuse_file *ff,
+						 u64 passthrough_ops)
 {
 #ifdef CONFIG_FUSE_PASSTHROUGH
+	if (!ff->passthrough)
+		return NULL;
+
+	if (ff->fm->fc->passthrough_ino && passthrough_ops) {
+		struct fuse_backing *fb = fuse_inode_backing(get_fuse_inode(inode));
+
+		if (!fb || (fb->ops_mask & passthrough_ops) != passthrough_ops)
+			return NULL;
+	}
+
 	return ff->passthrough;
 #else
 	return NULL;
diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 514e4af46d79..8ecce2a97ee8 100644
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -29,7 +29,7 @@ ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
 	struct fuse_file *ff = file->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
+	struct file *backing_file = ff->passthrough;
 	size_t count = iov_iter_count(iter);
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
@@ -56,7 +56,7 @@ ssize_t fuse_passthrough_write_iter(struct kiocb *iocb,
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
 	struct fuse_file *ff = file->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
+	struct file *backing_file = ff->passthrough;
 	size_t count = iov_iter_count(iter);
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
@@ -83,7 +83,7 @@ ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
 				     size_t len, unsigned int flags)
 {
 	struct fuse_file *ff = in->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
+	struct file *backing_file = ff->passthrough;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
 		.accessed = fuse_file_accessed,
@@ -107,8 +107,8 @@ ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
 				      size_t len, unsigned int flags)
 {
 	struct fuse_file *ff = out->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
 	struct inode *inode = file_inode(out);
+	struct file *backing_file = ff->passthrough;
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
@@ -132,7 +132,7 @@ ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
 ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct fuse_file *ff = file->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
+	struct file *backing_file = ff->passthrough;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
 		.accessed = fuse_file_accessed,
@@ -150,7 +150,7 @@ int fuse_passthrough_readdir(struct file *file, struct dir_context *ctx)
 	const struct cred *old_cred;
 	struct inode *inode = file_inode(file);
 	struct fuse_file *ff = file->private_data;
-	struct file *backing_file = fuse_file_passthrough(ff);
+	struct file *backing_file = ff->passthrough;
 	bool locked;
 
 	pr_debug("%s: backing_file=0x%p, pos=%lld\n", __func__,
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index 49226f022339..1f2ff63cd317 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -593,7 +593,7 @@ int fuse_readdir(struct file *file, struct dir_context *ctx)
 	if (fuse_is_bad(inode))
 		return -EIO;
 
-	if (fuse_file_passthrough(ff))
+	if (fuse_file_passthrough(inode, ff, FUSE_PASSTHROUGH_OP_READDIR))
 		return fuse_passthrough_readdir(file, ctx);
 
 	err = UNCACHED;
-- 
2.52.0