On Thu, 2023-01-05 at 14:02 +0000, Chuck Lever III wrote:
>
> > On Jan 5, 2023, at 6:23 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> >
> > Commit fb70bf124b05 ("NFSD: Instantiate a struct file when creating a
> > regular NFSv4 file") added the ability to cache an open fd over a
> > compound. There are a couple of problems with the way this currently
> > works:
> >
> > It's racy, as a newly-created nfsd_file can end up with its PENDING bit
> > cleared while the nf is hashed, and the nf_file pointer is still zeroed
> > out. Other tasks can find it in this state and they expect to see a
> > valid nf_file, and can oops if nf_file is NULL.
> >
> > Also, there is no guarantee that we'll end up creating a new nfsd_file
> > if one is already in the hash. If an extant entry is in the hash with a
> > valid nf_file, nfs4_get_vfs_file will clobber its nf_file pointer with
> > the value of op_file and the old nf_file will leak.
> >
> > Fix both issues by changing nfsd_file_acquire to take an optional file
> > pointer. If one is present when this is called, we'll take a new
> > reference to it instead of trying to open the file. If the nfsd_file
> > already has a valid nf_file, we'll just ignore the optional file and
> > pass the nfsd_file back as-is.
> >
> > Also rework the tracepoints a bit to allow for a cached open variant,
> > and don't try to avoid counting acquisitions in the case where we
> > already have a cached open file.
> >
> > Cc: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx>
> > Reported-by: Stanislav Saner <ssaner@xxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/nfsd/filecache.c | 49 ++++++++++++++----------------------------
> > fs/nfsd/filecache.h | 5 ++---
> > fs/nfsd/nfs4proc.c | 2 +-
> > fs/nfsd/nfs4state.c | 20 ++++++-----------
> > fs/nfsd/trace.h | 52 ++++++++++++---------------------------------
> > 5 files changed, 38 insertions(+), 90 deletions(-)
> >
> > v2: rebased directly onto current master branch to fix up some
> > contextual conflicts
>
> Hi Jeff-
>
> The basic race is that nf_file must be filled in before the PENDING
> bit is cleared. Got it.
>
That, and the fact that the nf_file pointer can be clobbered,
potentially leading to struct file leaks.
> Seems like -rc fodder, and needs a Fixes: tag.
>
> However, I'd prefer to keep the synopses of nfsd_file_acquire() and
> nfsd_file_acquire_gc() identical. nfs4_get_vfs_file() is the one
> spot that needs this special behavior, so it should continue to
> call nfsd_file_create(), or something like it. How about one of:
>
> nfsd_file_acquire2
> nfsd_file_acquire_create
> nfsd_file_acquire_cached
>
>
Ok, that's reasonable. I can respin it that way and will rebase onto
your current for-rc branch.
> > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> > index 45b2c9e3f636..6674a86e1917 100644
> > --- a/fs/nfsd/filecache.c
> > +++ b/fs/nfsd/filecache.c
> > @@ -1071,8 +1071,8 @@ nfsd_file_is_cached(struct inode *inode)
> >
> > static __be32
> > nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > - unsigned int may_flags, struct nfsd_file **pnf,
> > - bool open, bool want_gc)
> > + unsigned int may_flags, struct file *file,
> > + struct nfsd_file **pnf, bool want_gc)
> > {
> > struct nfsd_file_lookup_key key = {
> > .type = NFSD_FILE_KEY_FULL,
> > @@ -1147,8 +1147,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
> > out:
> > if (status == nfs_ok) {
> > - if (open)
> > - this_cpu_inc(nfsd_file_acquisitions);
> > + this_cpu_inc(nfsd_file_acquisitions);
> > *pnf = nf;
> > } else {
> > if (refcount_dec_and_test(&nf->nf_ref))
> > @@ -1158,20 +1157,23 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> >
> > out_status:
> > put_cred(key.cred);
> > - if (open)
> > - trace_nfsd_file_acquire(rqstp, key.inode, may_flags, nf, status);
> > + trace_nfsd_file_acquire(rqstp, key.inode, may_flags, nf, status);
> > return status;
> >
> > open_file:
> > trace_nfsd_file_alloc(nf);
> > nf->nf_mark = nfsd_file_mark_find_or_create(nf, key.inode);
> > if (nf->nf_mark) {
> > - if (open) {
> > + if (file) {
> > + get_file(file);
> > + nf->nf_file = file;
> > + status = nfs_ok;
> > + trace_nfsd_file_open_cached(nf, status);
> > + } else {
> > status = nfsd_open_verified(rqstp, fhp, may_flags,
> > &nf->nf_file);
> > trace_nfsd_file_open(nf, status);
> > - } else
> > - status = nfs_ok;
> > + }
> > } else
> > status = nfserr_jukebox;
> > /*
> > @@ -1207,7 +1209,7 @@ __be32
> > nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > unsigned int may_flags, struct nfsd_file **pnf)
> > {
> > - return nfsd_file_do_acquire(rqstp, fhp, may_flags, pnf, true, true);
> > + return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, true);
> > }
> >
> > /**
> > @@ -1215,6 +1217,7 @@ nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > * @rqstp: the RPC transaction being executed
> > * @fhp: the NFS filehandle of the file to be opened
> > * @may_flags: NFSD_MAY_ settings for the file
> > + * @file: cached, already-open file (may be NULL)
> > * @pnf: OUT: new or found "struct nfsd_file" object
> > *
> > * The nfsd_file_object returned by this API is reference-counted
> > @@ -1226,30 +1229,10 @@ nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > */
> > __be32
> > nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > - unsigned int may_flags, struct nfsd_file **pnf)
> > -{
> > - return nfsd_file_do_acquire(rqstp, fhp, may_flags, pnf, true, false);
> > -}
> > -
> > -/**
> > - * nfsd_file_create - Get a struct nfsd_file, do not open
> > - * @rqstp: the RPC transaction being executed
> > - * @fhp: the NFS filehandle of the file just created
> > - * @may_flags: NFSD_MAY_ settings for the file
> > - * @pnf: OUT: new or found "struct nfsd_file" object
> > - *
> > - * The nfsd_file_object returned by this API is reference-counted
> > - * but not garbage-collected. The object is released immediately
> > - * one RCU grace period after the final nfsd_file_put().
> > - *
> > - * Returns nfs_ok and sets @pnf on success; otherwise an nfsstat in
> > - * network byte order is returned.
> > - */
> > -__be32
> > -nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > - unsigned int may_flags, struct nfsd_file **pnf)
> > + unsigned int may_flags, struct file *file,
> > + struct nfsd_file **pnf)
> > {
> > - return nfsd_file_do_acquire(rqstp, fhp, may_flags, pnf, false, false);
> > + return nfsd_file_do_acquire(rqstp, fhp, may_flags, file, pnf, false);
> > }
> >
> > /*
> > diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
> > index b7efb2c3ddb1..ef0083cd4ea9 100644
> > --- a/fs/nfsd/filecache.h
> > +++ b/fs/nfsd/filecache.h
> > @@ -59,8 +59,7 @@ bool nfsd_file_is_cached(struct inode *inode);
> > __be32 nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > unsigned int may_flags, struct nfsd_file **nfp);
> > __be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > - unsigned int may_flags, struct nfsd_file **nfp);
> > -__be32 nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > - unsigned int may_flags, struct nfsd_file **nfp);
> > + unsigned int may_flags, struct file *file,
> > + struct nfsd_file **nfp);
> > int nfsd_file_cache_stats_show(struct seq_file *m, void *v);
> > #endif /* _FS_NFSD_FILECACHE_H */
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index bd880d55f565..6b09cdd4b067 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -735,7 +735,7 @@ nfsd4_commit(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > __be32 status;
> >
> > status = nfsd_file_acquire(rqstp, &cstate->current_fh, NFSD_MAY_WRITE |
> > - NFSD_MAY_NOT_BREAK_LEASE, &nf);
> > + NFSD_MAY_NOT_BREAK_LEASE, NULL, &nf);
> > if (status != nfs_ok)
> > return status;
> >
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 7b2ee535ade8..b68238024e49 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -5262,18 +5262,10 @@ static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
> > if (!fp->fi_fds[oflag]) {
> > spin_unlock(&fp->fi_lock);
> >
> > - if (!open->op_filp) {
> > - status = nfsd_file_acquire(rqstp, cur_fh, access, &nf);
> > - if (status != nfs_ok)
> > - goto out_put_access;
> > - } else {
> > - status = nfsd_file_create(rqstp, cur_fh, access, &nf);
> > - if (status != nfs_ok)
> > - goto out_put_access;
> > - nf->nf_file = open->op_filp;
> > - open->op_filp = NULL;
> > - trace_nfsd_file_create(rqstp, access, nf);
> > - }
> > + status = nfsd_file_acquire(rqstp, cur_fh, access,
> > + open->op_filp, &nf);
> > + if (status != nfs_ok)
> > + goto out_put_access;
> >
> > spin_lock(&fp->fi_lock);
> > if (!fp->fi_fds[oflag]) {
> > @@ -6472,7 +6464,7 @@ nfs4_check_file(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfs4_stid *s,
> > goto out;
> > }
> > } else {
> > - status = nfsd_file_acquire(rqstp, fhp, acc, &nf);
> > + status = nfsd_file_acquire(rqstp, fhp, acc, NULL, &nf);
> > if (status)
> > return status;
> > }
> > @@ -7644,7 +7636,7 @@ static __be32 nfsd_test_lock(struct svc_rqst *rqstp, struct svc_fh *fhp, struct
> > struct inode *inode;
> > __be32 err;
> >
> > - err = nfsd_file_acquire(rqstp, fhp, NFSD_MAY_READ, &nf);
> > + err = nfsd_file_acquire(rqstp, fhp, NFSD_MAY_READ, NULL, &nf);
> > if (err)
> > return err;
> > inode = fhp->fh_dentry->d_inode;
> > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > index c852ae8eaf37..7c6cbc37c8c9 100644
> > --- a/fs/nfsd/trace.h
> > +++ b/fs/nfsd/trace.h
> > @@ -981,43 +981,6 @@ TRACE_EVENT(nfsd_file_acquire,
> > )
> > );
> >
> > -TRACE_EVENT(nfsd_file_create,
> > - TP_PROTO(
> > - const struct svc_rqst *rqstp,
> > - unsigned int may_flags,
> > - const struct nfsd_file *nf
> > - ),
> > -
> > - TP_ARGS(rqstp, may_flags, nf),
> > -
> > - TP_STRUCT__entry(
> > - __field(const void *, nf_inode)
> > - __field(const void *, nf_file)
> > - __field(unsigned long, may_flags)
> > - __field(unsigned long, nf_flags)
> > - __field(unsigned long, nf_may)
> > - __field(unsigned int, nf_ref)
> > - __field(u32, xid)
> > - ),
> > -
> > - TP_fast_assign(
> > - __entry->nf_inode = nf->nf_inode;
> > - __entry->nf_file = nf->nf_file;
> > - __entry->may_flags = may_flags;
> > - __entry->nf_flags = nf->nf_flags;
> > - __entry->nf_may = nf->nf_may;
> > - __entry->nf_ref = refcount_read(&nf->nf_ref);
> > - __entry->xid = be32_to_cpu(rqstp->rq_xid);
> > - ),
> > -
> > - TP_printk("xid=0x%x inode=%p may_flags=%s ref=%u nf_flags=%s nf_may=%s nf_file=%p",
> > - __entry->xid, __entry->nf_inode,
> > - show_nfsd_may_flags(__entry->may_flags),
> > - __entry->nf_ref, show_nf_flags(__entry->nf_flags),
> > - show_nfsd_may_flags(__entry->nf_may), __entry->nf_file
> > - )
> > -);
> > -
> > TRACE_EVENT(nfsd_file_insert_err,
> > TP_PROTO(
> > const struct svc_rqst *rqstp,
> > @@ -1079,8 +1042,8 @@ TRACE_EVENT(nfsd_file_cons_err,
> > )
> > );
> >
> > -TRACE_EVENT(nfsd_file_open,
> > - TP_PROTO(struct nfsd_file *nf, __be32 status),
> > +DECLARE_EVENT_CLASS(nfsd_file_open_class,
> > + TP_PROTO(const struct nfsd_file *nf, __be32 status),
> > TP_ARGS(nf, status),
> > TP_STRUCT__entry(
> > __field(void *, nf_inode) /* cannot be dereferenced */
> > @@ -1104,6 +1067,17 @@ TRACE_EVENT(nfsd_file_open,
> > __entry->nf_file)
> > )
> >
> > +#define DEFINE_NFSD_FILE_OPEN_EVENT(name) \
> > +DEFINE_EVENT(nfsd_file_open_class, name, \
> > + TP_PROTO( \
> > + const struct nfsd_file *nf, \
> > + __be32 status \
> > + ), \
> > + TP_ARGS(nf, status))
> > +
> > +DEFINE_NFSD_FILE_OPEN_EVENT(nfsd_file_open);
> > +DEFINE_NFSD_FILE_OPEN_EVENT(nfsd_file_open_cached);
> > +
> > TRACE_EVENT(nfsd_file_is_cached,
> > TP_PROTO(
> > const struct inode *inode,
> > --
> > 2.39.0
> >
>
> --
> Chuck Lever
>
>
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
