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-rw-r--r--fs/nfsd/nfs4state.c97
-rw-r--r--fs/nfsd/trace.h1
2 files changed, 78 insertions, 20 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index b56ea72d4350..8534693eb6a4 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -649,6 +649,18 @@ 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)
{
@@ -1144,7 +1156,7 @@ static void block_delegations(struct knfsd_fh *fh)
static struct nfs4_delegation *
alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
- struct nfs4_clnt_odstate *odstate)
+ struct nfs4_clnt_odstate *odstate, u32 dl_type)
{
struct nfs4_delegation *dp;
long n;
@@ -1170,7 +1182,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
INIT_LIST_HEAD(&dp->dl_recall_lru);
dp->dl_clnt_odstate = odstate;
get_clnt_odstate(odstate);
- dp->dl_type = NFS4_OPEN_DELEGATE_READ;
+ dp->dl_type = dl_type;
dp->dl_retries = 1;
dp->dl_recalled = false;
nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
@@ -5449,8 +5461,9 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
struct nfs4_file *fp = stp->st_stid.sc_file;
struct nfs4_clnt_odstate *odstate = stp->st_clnt_odstate;
struct nfs4_delegation *dp;
- struct nfsd_file *nf;
+ struct nfsd_file *nf = NULL;
struct file_lock *fl;
+ u32 dl_type;
/*
* The fi_had_conflict and nfs_get_existing_delegation checks
@@ -5460,15 +5473,35 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
if (fp->fi_had_conflict)
return ERR_PTR(-EAGAIN);
- nf = find_readable_file(fp);
- if (!nf) {
- /*
- * We probably could attempt another open and get a read
- * delegation, but for now, don't bother until the
- * client actually sends us one.
- */
- return ERR_PTR(-EAGAIN);
+ /*
+ * Try for a write delegation first. RFC8881 section 10.4 says:
+ *
+ * "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.
+ *
+ * Offer a write delegation in the case of a BOTH open, and ensure
+ * we get the O_RDWR descriptor.
+ */
+ if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) {
+ nf = find_rw_file(fp);
+ dl_type = NFS4_OPEN_DELEGATE_WRITE;
}
+
+ /*
+ * If the file is being opened O_RDONLY or we couldn't get a O_RDWR
+ * file for some reason, then try for a read delegation instead.
+ */
+ if (!nf && (open->op_share_access & NFS4_SHARE_ACCESS_READ)) {
+ nf = find_readable_file(fp);
+ dl_type = NFS4_OPEN_DELEGATE_READ;
+ }
+
+ if (!nf)
+ return ERR_PTR(-EAGAIN);
+
spin_lock(&state_lock);
spin_lock(&fp->fi_lock);
if (nfs4_delegation_exists(clp, fp))
@@ -5491,11 +5524,11 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
return ERR_PTR(status);
status = -ENOMEM;
- dp = alloc_init_deleg(clp, fp, odstate);
+ dp = alloc_init_deleg(clp, fp, odstate, dl_type);
if (!dp)
goto out_delegees;
- fl = nfs4_alloc_init_lease(dp, NFS4_OPEN_DELEGATE_READ);
+ fl = nfs4_alloc_init_lease(dp, dl_type);
if (!fl)
goto out_clnt_odstate;
@@ -5568,10 +5601,28 @@ static void nfsd4_open_deleg_none_ext(struct nfsd4_open *open, int status)
}
/*
- * Attempt to hand out a delegation.
+ * The Linux NFS server does not offer write delegations to NFSv4.0
+ * clients in order to avoid conflicts between write delegations and
+ * GETATTRs requesting CHANGE or SIZE attributes.
+ *
+ * With NFSv4.1 and later minorversions, the SEQUENCE operation that
+ * begins each COMPOUND contains a client ID. Delegation recall can
+ * be avoided when the server recognizes the client sending a
+ * GETATTR also holds write delegation it conflicts with.
+ *
+ * However, the NFSv4.0 protocol does not enable a server to
+ * determine that a GETATTR originated from the client holding the
+ * conflicting delegation versus coming from some other client. Per
+ * RFC 7530 Section 16.7.5, the server must recall or send a
+ * CB_GETATTR even when the GETATTR originates from the client that
+ * holds the conflicting delegation.
*
- * Note we don't support write delegations, and won't until the vfs has
- * proper support for them.
+ * An NFSv4.0 client can trigger a pathological situation if it
+ * always sends a DELEGRETURN preceded by a conflicting GETATTR in
+ * the same COMPOUND. COMPOUND execution will always stop at the
+ * GETATTR and the DELEGRETURN will never get executed. The server
+ * eventually revokes the delegation, which can result in loss of
+ * open or lock state.
*/
static void
nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
@@ -5590,8 +5641,6 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
case NFS4_OPEN_CLAIM_PREVIOUS:
if (!cb_up)
open->op_recall = 1;
- if (open->op_delegate_type != NFS4_OPEN_DELEGATE_READ)
- goto out_no_deleg;
break;
case NFS4_OPEN_CLAIM_NULL:
parent = currentfh;
@@ -5606,6 +5655,9 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
goto out_no_deleg;
if (!cb_up || !(oo->oo_flags & NFS4_OO_CONFIRMED))
goto out_no_deleg;
+ if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE &&
+ !clp->cl_minorversion)
+ goto out_no_deleg;
break;
default:
goto out_no_deleg;
@@ -5616,8 +5668,13 @@ 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));
- trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
- open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
+ if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
+ open->op_delegate_type = NFS4_OPEN_DELEGATE_WRITE;
+ trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
+ } else {
+ open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
+ trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
+ }
nfs4_put_stid(&dp->dl_stid);
return;
out_no_deleg:
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 2af74983f146..693fe6d465aa 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -607,6 +607,7 @@ DEFINE_STATEID_EVENT(layout_recall_release);
DEFINE_STATEID_EVENT(open);
DEFINE_STATEID_EVENT(deleg_read);
+DEFINE_STATEID_EVENT(deleg_write);
DEFINE_STATEID_EVENT(deleg_return);
DEFINE_STATEID_EVENT(deleg_recall);
generated by cgit v1.2.3 (git 2.39.0) at 2024-07-23 05:24:34 +0300