[RFC PATCH v2 09/21] fuse-bpf: Add lseek support

Daniel Rosenberg
2022-11-22T02:17:22Z

fs/fuse/backing.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++
fs/fuse/file.c | 3 ++
fs/fuse/fuse_i.h | 6 ++++
3 files changed, 97 insertions(+)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index 8d862bc64acd..76f48872ed35 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -205,6 +205,94 @@ static void fuse_stat_to_attr(struct fuse_conn *fc, struct inode *inode,
attr->blksize = 1 << blkbits;
}

+struct fuse_lseek_io {
+ struct fuse_lseek_in fli;
+ struct fuse_lseek_out flo;
+};
+
+static int fuse_lseek_initialize_in(struct fuse_args *fa, struct fuse_lseek_io *flio,
+ struct file *file, loff_t offset, int whence)
+{
+ struct fuse_file *fuse_file = file->private_data;
+
+ flio->fli = (struct fuse_lseek_in) {
+ .fh = fuse_file->fh,
+ .offset = offset,
+ .whence = whence,
+ };
+
+ *fa = (struct fuse_args) {
+ .nodeid = get_node_id(file->f_inode),
+ .opcode = FUSE_LSEEK,
+ .in_numargs = 1,
+ .in_args[0].size = sizeof(flio->fli),
+ .in_args[0].value = &flio->fli,
+ };
+
+ return 0;
+}
+
+static int fuse_lseek_initialize_out(struct fuse_args *fa, struct fuse_lseek_io *flio,
+ struct file *file, loff_t offset, int whence)
+{
+ fa->out_numargs = 1;
+ fa->out_args[0].size = sizeof(flio->flo);
+ fa->out_args[0].value = &flio->flo;
+
+ return 0;
+}
+
+static int fuse_lseek_backing(struct 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 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->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 fuse_bpf_backing(inode, struct fuse_lseek_io, 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 24fd4f33105c..e90b3e2d5452 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2704,6 +2704,9 @@ 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 95d67afcff05..108c2ea15a49 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1400,11 +1400,17 @@ 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;
--
2.38.1.584.g0f3c55d4c2-goog