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    Subject[RFC PATCH v2 09/21] fuse-bpf: Add lseek support
    From
    Signed-off-by: Daniel Rosenberg <drosen@google.com>
    Signed-off-by: Paul Lawrence <paullawrence@google.com>
    ---
    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
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