[RFC PATCH v4 09/36] fuse-bpf: Add lseek support

Daniel Rosenberg
2024-03-29T01:54:19Z

This adds backing support for FUSE_LSEEK

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Paul Lawrence <paullawrence@google.com>
---
fs/fuse/backing.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++
fs/fuse/file.c | 3 ++
fs/fuse/fuse_i.h | 6 ++++
3 files changed, 98 insertions(+)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index 331b3f23ef78..04cb0c0c10b0 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -210,6 +210,95 @@ static void fuse_stat_to_attr(struct fuse_conn *fc, struct inode *inode,
attr->blksize = 1 << blkbits;
}

+struct fuse_lseek_args {
+ struct fuse_lseek_in in;
+ struct fuse_lseek_out out;
+};
+
+static int fuse_lseek_initialize_in(struct bpf_fuse_args *fa, struct fuse_lseek_args *args,
+ struct file *file, loff_t offset, int whence)
+{
+ struct fuse_file *fuse_file = file->private_data;
+
+ args->in = (struct fuse_lseek_in) {
+ .fh = fuse_file->fh,
+ .offset = offset,
+ .whence = whence,
+ };
+
+ *fa = (struct bpf_fuse_args) {
+ .info = (struct bpf_fuse_meta_info) {
+ .nodeid = get_node_id(file->f_inode),
+ .opcode = FUSE_LSEEK,
+ },
+ .in_numargs = 1,
+ .in_args[0].size = sizeof(args->in),
+ .in_args[0].value = &args->in,
+ };
+
+ return 0;
+}
+
+static int fuse_lseek_initialize_out(struct bpf_fuse_args *fa, struct fuse_lseek_args *args,
+ struct file *file, loff_t offset, int whence)
+{
+ fa->out_numargs = 1;
+ fa->out_args[0].size = sizeof(args->out);
+ fa->out_args[0].value = &args->out;
+
+ return 0;
+}
+
+static int fuse_lseek_backing(struct bpf_fuse_args *fa, loff_t *out,
+ struct file *file, loff_t offset, int whence)
+{
+ const struct fuse_lseek_in *fli = fa->in_args[0].value;
+ struct fuse_lseek_out *flo = fa->out_args[0].value;
+ struct fuse_file *fuse_file = file->private_data;
+ struct file *backing_file = fuse_file->backing_file;
+
+ /* TODO: Handle changing of the file handle */
+ if (offset == 0) {
+ if (whence == SEEK_CUR) {
+ flo->offset = file->f_pos;
+ *out = flo->offset;
+ return 0;
+ }
+
+ if (whence == SEEK_SET) {
+ flo->offset = vfs_setpos(file, 0, 0);
+ *out = flo->offset;
+ return 0;
+ }
+ }
+
+ inode_lock(file->f_inode);
+ backing_file->f_pos = file->f_pos;
+ *out = vfs_llseek(backing_file, fli->offset, fli->whence);
+ flo->offset = *out;
+ inode_unlock(file->f_inode);
+ return 0;
+}
+
+static int fuse_lseek_finalize(struct bpf_fuse_args *fa, loff_t *out,
+ struct file *file, loff_t offset, int whence)
+{
+ struct fuse_lseek_out *flo = fa->out_args[0].value;
+
+ if (!fa->info.error_in)
+ file->f_pos = flo->offset;
+ *out = flo->offset;
+ return 0;
+}
+
+int fuse_bpf_lseek(loff_t *out, struct inode *inode, struct file *file, loff_t offset, int whence)
+{
+ return bpf_fuse_backing(inode, struct fuse_lseek_args, out,
+ fuse_lseek_initialize_in, fuse_lseek_initialize_out,
+ fuse_lseek_backing, fuse_lseek_finalize,
+ file, offset, whence);
+}
+
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 b15a0c30fec8..b3cae6e677f8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2740,6 +2740,9 @@ static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
loff_t retval;
struct inode *inode = file_inode(file);

+ if (fuse_bpf_lseek(&retval, inode, file, offset, whence))
+ return retval;
+
switch (whence) {
case SEEK_SET:
case SEEK_CUR:
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5f76ba3c1e4b..24f453d162ae 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1438,11 +1438,17 @@ int parse_fuse_bpf_entry(struct fuse_bpf_entry *fbe, int num_entries);

#ifdef CONFIG_FUSE_BPF

+int fuse_bpf_lseek(loff_t *out, struct inode *inode, struct file *file, loff_t offset, int whence);
int fuse_bpf_lookup(struct dentry **out, struct inode *dir, struct dentry *entry, unsigned int flags);
int fuse_bpf_access(int *out, struct inode *inode, int mask);

#else

+static inline int fuse_bpf_lseek(loff_t *out, struct inode *inode, struct file *file, loff_t offset, int whence)
+{
+ return 0;
+}
+
static inline int fuse_bpf_lookup(struct dentry **out, struct inode *dir, struct dentry *entry, unsigned int flags)
{
return 0;
--
2.44.0.478.gd926399ef9-goog