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nfsd: fix handling of cached open files in nfsd4_open codepath

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Commit fb70bf124b ("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 making a new nfsd_file_acquirei_opened variant that
takes 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 an "opened" variant and
don't try to avoid counting acquisitions in the case where we already
have a cached open file.

Fixes: fb70bf124b ("NFSD: Instantiate a struct file when creating a regular NFSv4 file")
Cc: Trond Myklebust <trondmy@hammerspace.com>
Reported-by: Stanislav Saner <ssaner@redhat.com>
Reported-and-Tested-by: Ruben Vestergaard <rubenv@drcmr.dk>
Reported-and-Tested-by: Torkil Svensgaard <torkil@drcmr.dk>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Jeff Layton 2023-01-05 14:55:56 -05:00 committed by Chuck Lever
parent cad853374d
commit 0b3a551fa5
4 changed files with 42 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
fs/nfsd/filecache.c
View File

@ -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 @@ wait_for_construction:
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 @@ out:
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_opened(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);
}
/**
@ -1228,28 +1230,30 @@ __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);
return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, false);
}
/**
* nfsd_file_create - Get a struct nfsd_file, do not open
* nfsd_file_acquire_opened - Get a struct nfsd_file using existing open file
* @rqstp: the RPC transaction being executed
* @fhp: the NFS filehandle of the file just created
* @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
* but not garbage-collected. The object is released immediately
* one RCU grace period after the final nfsd_file_put().
* Acquire a nfsd_file object that is not GC'ed. If one doesn't already exist,
* and @file is non-NULL, use it to instantiate a new nfsd_file instead of
* opening a new one.
*
* 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)
nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
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);
}
/*

5
fs/nfsd/filecache.h
View File

@ -60,7 +60,8 @@ __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);
__be32 nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
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 */

16
fs/nfsd/nfs4state.c
View File

@ -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_opened(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]) {

52
fs/nfsd/trace.h
View File

@ -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_opened);
TRACE_EVENT(nfsd_file_is_cached,
TP_PROTO(
const struct inode *inode,