[RFC PATCH v4 21/36] fuse-bpf: Add partial flock support

Daniel Rosenberg
2024-03-29T01:54:46Z

This adds passthrough support for flock on fuse-bpf files. It does not
give any control via a bpf filter. The flock will act as though it was
taken on the lower file.

see fuse_test -t32 (flock_test)

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
fs/fuse/backing.c | 15 +++++++++++++++
fs/fuse/file.c | 9 +++++++--
fs/fuse/fuse_i.h | 1 +
3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index f18aee297335..b2df2469c29c 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -9,6 +9,7 @@
#include <linux/bpf_fuse.h>
#include <linux/fdtable.h>
#include <linux/file.h>
+#include <linux/filelock.h>
#include <linux/fs_stack.h>
#include <linux/namei.h>
#include <linux/splice.h>
@@ -1586,6 +1587,20 @@ int fuse_bpf_file_write_iter(ssize_t *out, struct inode *inode, struct kiocb *io
iocb, from);
}

+int fuse_file_flock_backing(struct file *file, int cmd, struct file_lock *fl)
+{
+ struct fuse_file *ff = file->private_data;
+ struct file *backing_file = ff->backing_file;
+ int error;
+
+ fl->fl_file = backing_file;
+ if (backing_file->f_op->flock)
+ error = backing_file->f_op->flock(backing_file, cmd, fl);
+ else
+ error = locks_lock_file_wait(backing_file, fl);
+ return error;
+}
+
ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma)
{
int ret;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 46de67810f03..255eb59d04f8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2676,13 +2676,18 @@ static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
{
struct inode *inode = file_inode(file);
struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_file *ff = file->private_data;
int err;

+#ifdef CONFIG_FUSE_BPF
+ /* TODO - this is simply passthrough, not a proper BPF filter */
+ if (ff->backing_file)
+ return fuse_file_flock_backing(file, cmd, fl);
+#endif
+
if (fc->no_flock) {
err = locks_lock_file_wait(file, fl);
} else {
- struct fuse_file *ff = file->private_data;
-
/* emulate flock with POSIX locks */
ff->flock = true;
err = fuse_setlk(file, fl, 1);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 8ae6ad967f95..e69f83616909 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1651,6 +1651,7 @@ static inline int fuse_bpf_access(int *out, struct inode *inode, int mask)

#endif // CONFIG_FUSE_BPF

+int fuse_file_flock_backing(struct file *file, int cmd, struct file_lock *fl);
ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma);

int fuse_handle_backing(struct fuse_bpf_entry *fbe, struct path *backing_path);
--
2.44.0.478.gd926399ef9-goog