On Thu, Nov 14, 2024 at 1:05 PM Bernd Schubert
<bernd.schubert@xxxxxxxxxxx> wrote:
>
>
>
> On 11/14/24 21:57, Joanne Koong wrote:
> > On Thu, Nov 7, 2024 at 9:04 AM Bernd Schubert <bschubert@xxxxxxx> wrote:
> >>
> >> This change sets up FUSE operations to have headers in args.in_args[0],
> >> even for opcodes without an actual header. We do this to prepare for
> >> cleanly separating payload from headers in the future.
> >>
> >> For opcodes without a header, we use a zero-sized struct as a
> >> placeholder. This approach:
> >> - Keeps things consistent across all FUSE operations
> >> - Will help with payload alignment later
> >> - Avoids future issues when header sizes change
> >>
> >> Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
> >> ---
> >> fs/fuse/dax.c | 13 ++++++++-----
> >> fs/fuse/dev.c | 24 ++++++++++++++++++++----
> >> fs/fuse/dir.c | 41 +++++++++++++++++++++++++++--------------
> >> fs/fuse/fuse_i.h | 7 +++++++
> >> fs/fuse/xattr.c | 9 ++++++---
> >> 5 files changed, 68 insertions(+), 26 deletions(-)
> >>
> >> diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
> >> index 12ef91d170bb3091ac35a33d2b9dc38330b00948..e459b8134ccb089f971bebf8da1f7fc5199c1271 100644
> >> --- a/fs/fuse/dax.c
> >> +++ b/fs/fuse/dax.c
> >> @@ -237,14 +237,17 @@ static int fuse_send_removemapping(struct inode *inode,
> >> struct fuse_inode *fi = get_fuse_inode(inode);
> >> struct fuse_mount *fm = get_fuse_mount(inode);
> >> FUSE_ARGS(args);
> >> + struct fuse_zero_in zero_arg;
> >>
> >> args.opcode = FUSE_REMOVEMAPPING;
> >> args.nodeid = fi->nodeid;
> >> - args.in_numargs = 2;
> >> - args.in_args[0].size = sizeof(*inargp);
> >> - args.in_args[0].value = inargp;
> >> - args.in_args[1].size = inargp->count * sizeof(*remove_one);
> >> - args.in_args[1].value = remove_one;
> >> + args.in_numargs = 3;
> >> + args.in_args[0].size = sizeof(zero_arg);
> >> + args.in_args[0].value = &zero_arg;
> >> + args.in_args[1].size = sizeof(*inargp);
> >> + args.in_args[1].value = inargp;
> >> + args.in_args[2].size = inargp->count * sizeof(*remove_one);
> >> + args.in_args[2].value = remove_one;
> >> return fuse_simple_request(fm, &args);
> >> }
> >>
> >> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> >> index dbc222f9b0f0e590ce3ef83077e6b4cff03cff65..6effef4073da3dad2f6140761eca98147a41d88d 100644
> >> --- a/fs/fuse/dev.c
> >> +++ b/fs/fuse/dev.c
> >> @@ -1007,6 +1007,19 @@ static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
> >>
> >> for (i = 0; !err && i < numargs; i++) {
> >> struct fuse_arg *arg = &args[i];
> >> +
> >> + /* zero headers */
> >> + if (arg->size == 0) {
> >> + if (WARN_ON_ONCE(i != 0)) {
> >> + if (cs->req)
> >> + pr_err_once(
> >> + "fuse: zero size header in opcode %d\n",
> >> + cs->req->in.h.opcode);
> >> + return -EINVAL;
> >> + }
> >> + continue;
> >> + }
> >> +
> >> if (i == numargs - 1 && argpages)
> >> err = fuse_copy_pages(cs, arg->size, zeroing);
> >> else
> >> @@ -1662,6 +1675,7 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
> >> size_t args_size = sizeof(*ra);
> >> struct fuse_args_pages *ap;
> >> struct fuse_args *args;
> >> + struct fuse_zero_in zero_arg;
> >>
> >> offset = outarg->offset & ~PAGE_MASK;
> >> file_size = i_size_read(inode);
> >> @@ -1688,7 +1702,7 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
> >> args = &ap->args;
> >> args->nodeid = outarg->nodeid;
> >> args->opcode = FUSE_NOTIFY_REPLY;
> >> - args->in_numargs = 2;
> >> + args->in_numargs = 3;
> >> args->in_pages = true;
> >> args->end = fuse_retrieve_end;
> >>
> >> @@ -1715,9 +1729,11 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
> >> }
> >> ra->inarg.offset = outarg->offset;
> >> ra->inarg.size = total_len;
> >> - args->in_args[0].size = sizeof(ra->inarg);
> >> - args->in_args[0].value = &ra->inarg;
> >> - args->in_args[1].size = total_len;
> >> + args->in_args[0].size = sizeof(zero_arg);
> >> + args->in_args[0].value = &zero_arg;
> >> + args->in_args[1].size = sizeof(ra->inarg);
> >> + args->in_args[1].value = &ra->inarg;
> >> + args->in_args[2].size = total_len;
> >>
> >> err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
> >> if (err)
> >
> > Do we also need to add a zero arg header for FUSE_READLINK,
> > FUSE_DESTROY, and FUSE_BATCH_FORGET requests as well?
> >
>
> Thanks for looking at the patch! I should have added to the commit message
> that I didn't modify these, as they don't have an in argument at all.
>
Thanks for clarifying! (and apologies for the late review. I haven't
been keeping up with these patches since RFC v3 but I'm planning to
get up to speed and take a deeper look at these tomorrow + next week).
I think the FUSE_BATCH_FORGET request does use in args, depending on
the number of forget requests.
Thanks,
Joanne
>
> Thanks,
> Bernd
