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NFSD: Offer write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE

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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 allows 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@oracle.com>
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Dai Ngo
2025-05-13 09:08:28 -07:00
committed by Chuck Lever
parent 347e9f5043
commit e7a8ebc305
1 changed files with 47 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

75
fs/nfsd/nfs4state.c
View File

@@ -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)
{
@@ -6000,14 +5988,19 @@ 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:
*
* Offer a write delegation in the case of a BOTH open, and ensure
* we get the O_RDWR descriptor.
* "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)."
*
* 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;
}
@@ -6138,7 +6131,7 @@ 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;
@@ -6156,6 +6149,33 @@ 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
@@ -6181,8 +6201,9 @@ 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)
{
struct nfs4_openowner *oo = openowner(stp->st_stateowner);
bool deleg_ts = nfsd4_want_deleg_timestamps(open);
@@ -6227,7 +6248,8 @@ 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;
@@ -6383,7 +6405,8 @@ 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
@@ -7076,7 +7099,7 @@ 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;
@@ -7119,10 +7142,6 @@ 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)