On Sun, Sep 14, 2025 at 11:05:08AM +1000, NeilBrown wrote:
> READDIR without establishing and "open" state.
>
> Why do you think nfs4_opendata_access() expects the possibilty of a
> directory?
static int nfs4_opendata_access(const struct cred *cred,
struct nfs4_opendata *opendata,
struct nfs4_state *state, fmode_t fmode)
{
struct nfs_access_entry cache;
u32 mask, flags;
/* access call failed or for some reason the server doesn't
* support any access modes -- defer access call until later */
if (opendata->o_res.access_supported == 0)
return 0;
mask = 0;
if (fmode & FMODE_EXEC) {
/* ONLY check for exec rights */
if (S_ISDIR(state->inode->i_mode))
^^^^^^^
How else would you describe this?
mask = NFS4_ACCESS_LOOKUP;
else
mask = NFS4_ACCESS_EXECUTE;
> > if (d_inode(dentry) == state->inode)
> > nfs_inode_attach_open_context(ctx);
> > shortly afterwards (incidentally, what is that check about? It can only
> > fail in case of nfs4_file_open(); should we have open(2) succeed in such
> > situation?)
>
> I don't know what is going on here.
> Based on the commit that introduced this code
>
> Commit: c45ffdd26961 ("NFSv4: Close another NFSv4 recovery race")
>
> there is presumably some race that can cause the test to fail.
> Maybe Trond (cc:ed) could help explain.
AFAICS, it can happen if you are there from nfs4_file_open(), hit
_nfs4_opendata_to_nfs4_state(opendata), find ->rpc_done to be true
in there, hit nfs4_opendata_find_nfs4_state(), have it call
nfs4_opendata_get_inode() and run into a server without
NFS_CAP_ATOMIC_OPEN_V1. Then you get ->o_arg.claim set to
NFS4_OPEN_CLAIM_NULL and hit this:
inode = nfs_fhget(data->dir->d_sb, &data->o_res.fh,
&data->f_attr);
finding not the same inode as your dentry has attached to it.
So the test might end up not being true, at least from my reading of
that code.
What I don't understand is the reasons for not failing immediately
with EOPENSTALE in that case.
TBH, I would be a lot more comfortable if the "attach inode to dentry"
logics in there had been taken several levels up the call chains - analysis
would be much easier that way...
