RFC8881, section 9.1.2 says:
"In the case of READ, the server may perform the corresponding
check on the access mode, or it may choose to allow READ for
OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
implementation may unavoidably do reads (e.g., due to buffer cache
constraints)."
and in section 10.4.1:
"Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/
OPEN4_SHARE_ACCESS_BOTH and if an OPEN_DELEGATE_WRITE delegation
is in effect"
This patch allow READ using write delegation stateid granted on OPENs
with OPEN4_SHARE_ACCESS_WRITE only, to accommodate clients whose WRITE
implementation may unavoidably do (e.g., due to buffer cache
constraints).
For write delegation granted for OPEN with OPEN4_SHARE_ACCESS_WRITE
a new nfsd_file and a struct file are allocated to use for reads.
The nfsd_file is freed when the file is closed by release_all_access.
Suggested-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/nfsd/nfs4state.c | 75 ++++++++++++++++++++++++++++-----------------
1 file changed, 47 insertions(+), 28 deletions(-)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 0f97f2c62b3a..295415fda985 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -633,18 +633,6 @@ find_readable_file(struct nfs4_file *f)
return ret;
}
-static struct nfsd_file *
-find_rw_file(struct nfs4_file *f)
-{
- struct nfsd_file *ret;
-
- spin_lock(&f->fi_lock);
- ret = nfsd_file_get(f->fi_fds[O_RDWR]);
- spin_unlock(&f->fi_lock);
-
- return ret;
-}
-
struct nfsd_file *
find_any_file(struct nfs4_file *f)
{
@@ -5987,14 +5975,19 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
* "An OPEN_DELEGATE_WRITE delegation allows the client to handle,
* on its own, all opens."
*
- * Furthermore the client can use a write delegation for most READ
- * operations as well, so we require a O_RDWR file here.
+ * Furthermore, section 9.1.2 says:
+ *
+ * "In the case of READ, the server may perform the corresponding
+ * check on the access mode, or it may choose to allow READ for
+ * OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
+ * implementation may unavoidably do reads (e.g., due to buffer
+ * cache constraints)."
*
- * Offer a write delegation in the case of a BOTH open, and ensure
- * we get the O_RDWR descriptor.
+ * We choose to offer a write delegation for OPEN with the
+ * OPEN4_SHARE_ACCESS_WRITE access mode to accommodate such clients.
*/
- if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) {
- nf = find_rw_file(fp);
+ if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
+ nf = find_writeable_file(fp);
dl_type = deleg_ts ? OPEN_DELEGATE_WRITE_ATTRS_DELEG : OPEN_DELEGATE_WRITE;
}
@@ -6116,7 +6109,7 @@ static bool
nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
struct kstat *stat)
{
- struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);
+ struct nfsd_file *nf = find_writeable_file(dp->dl_stid.sc_file);
struct path path;
int rc;
@@ -6134,6 +6127,33 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
return rc == 0;
}
+/*
+ * Add NFS4_SHARE_ACCESS_READ to the write delegation granted on OPEN
+ * with NFS4_SHARE_ACCESS_WRITE by allocating separate nfsd_file and
+ * struct file to be used for read with delegation stateid.
+ *
+ */
+static bool
+nfsd4_add_rdaccess_to_wrdeleg(struct svc_rqst *rqstp, struct nfsd4_open *open,
+ struct svc_fh *fh, struct nfs4_ol_stateid *stp)
+{
+ struct nfs4_file *fp;
+ struct nfsd_file *nf = NULL;
+
+ if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) ==
+ NFS4_SHARE_ACCESS_WRITE) {
+ if (nfsd_file_acquire_opened(rqstp, fh, NFSD_MAY_READ, NULL, &nf))
+ return (false);
+ fp = stp->st_stid.sc_file;
+ spin_lock(&fp->fi_lock);
+ __nfs4_file_get_access(fp, NFS4_SHARE_ACCESS_READ);
+ fp = stp->st_stid.sc_file;
+ fp->fi_fds[O_RDONLY] = nf;
+ spin_unlock(&fp->fi_lock);
+ }
+ return true;
+}
+
/*
* The Linux NFS server does not offer write delegations to NFSv4.0
* clients in order to avoid conflicts between write delegations and
@@ -6159,8 +6179,9 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
* open or lock state.
*/
static void
-nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
- struct svc_fh *currentfh)
+nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open,
+ struct nfs4_ol_stateid *stp, struct svc_fh *currentfh,
+ struct svc_fh *fh)
{
bool deleg_ts = open->op_deleg_want & OPEN4_SHARE_ACCESS_WANT_DELEG_TIMESTAMPS;
struct nfs4_openowner *oo = openowner(stp->st_stateowner);
@@ -6205,7 +6226,8 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
memcpy(&open->op_delegate_stateid, &dp->dl_stid.sc_stateid, sizeof(dp->dl_stid.sc_stateid));
if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
- if (!nfs4_delegation_stat(dp, currentfh, &stat)) {
+ if (!nfsd4_add_rdaccess_to_wrdeleg(rqstp, open, fh, stp) ||
+ !nfs4_delegation_stat(dp, currentfh, &stat)) {
nfs4_put_stid(&dp->dl_stid);
destroy_delegation(dp);
goto out_no_deleg;
@@ -6361,7 +6383,8 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
* Attempt to hand out a delegation. No error return, because the
* OPEN succeeds even if we fail.
*/
- nfs4_open_delegation(open, stp, &resp->cstate.current_fh);
+ nfs4_open_delegation(rqstp, open, stp,
+ &resp->cstate.current_fh, current_fh);
/*
* If there is an existing open stateid, it must be updated and
@@ -7063,7 +7086,7 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
return_revoked = true;
if (typemask & SC_TYPE_DELEG)
/* Always allow REVOKED for DELEG so we can
- * retturn the appropriate error.
+ * return the appropriate error.
*/
statusmask |= SC_STATUS_REVOKED;
@@ -7106,10 +7129,6 @@ nfs4_find_file(struct nfs4_stid *s, int flags)
switch (s->sc_type) {
case SC_TYPE_DELEG:
- spin_lock(&s->sc_file->fi_lock);
- ret = nfsd_file_get(s->sc_file->fi_deleg_file);
- spin_unlock(&s->sc_file->fi_lock);
- break;
case SC_TYPE_OPEN:
case SC_TYPE_LOCK:
if (flags & RD_STATE)
