From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
It's OK to grant a read delegation to a client that holds a write, as
long as it's the only client holding the write.
We originally tried to do this in 94415b06eb8a "nfsd4: a client's own
opens needn't prevent delegations", which had to be reverted in
6ee65a773096.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
fs/locks.c | 3 ++
fs/nfsd/nfs4state.c | 82 +++++++++++++++++++++++++++++++++++++--------
2 files changed, 71 insertions(+), 14 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index 6125d2de39b8..bcc71c469ede 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1808,6 +1808,9 @@ check_conflicting_open(struct file *filp, const long arg, int flags)
if (flags & FL_LAYOUT)
return 0;
+ if (flags & FL_DELEG)
+ /* We leave these checks to the caller */
+ return 0;
if (arg == F_RDLCK)
return inode_is_open_for_write(inode) ? -EAGAIN : 0;
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index dfe3e39c891c..5c4896773bdd 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4976,6 +4976,65 @@ static struct file_lock *nfs4_alloc_init_lease(struct nfs4_delegation *dp,
return fl;
}
+static int nfsd4_check_conflicting_opens(struct nfs4_client *clp,
+ struct nfs4_file *fp)
+{
+ struct nfs4_ol_stateid *st;
+ struct file *f = fp->fi_deleg_file->nf_file;
+ struct inode *ino = locks_inode(f);
+ int writes;
+
+ writes = atomic_read(&ino->i_writecount);
+ if (!writes)
+ return 0;
+ /*
+ * There could be multiple filehandles (hence multiple
+ * nfs4_files) referencing this file, but that's not too
+ * common; let's just give up in that case rather than
+ * trying to go look up all the clients using that other
+ * nfs4_file as well:
+ */
+ if (fp->fi_aliased)
+ return -EAGAIN;
+ /*
+ * If there's a close in progress, make sure that we see it
+ * clear any fi_fds[] entries before we see it decrement
+ * i_writecount:
+ */
+ smp_mb__after_atomic();
+
+ if (fp->fi_fds[O_WRONLY])
+ writes--;
+ if (fp->fi_fds[O_RDWR])
+ writes--;
+ if (writes > 0)
+ return -EAGAIN; /* There may be non-NFSv4 writers */
+ /*
+ * It's possible there are non-NFSv4 write opens in progress,
+ * but if they haven't incremented i_writecount yet then they
+ * also haven't called break lease yet; so, they'll break this
+ * lease soon enough. So, all that's left to check for is NFSv4
+ * opens:
+ */
+ spin_lock(&fp->fi_lock);
+ list_for_each_entry(st, &fp->fi_stateids, st_perfile) {
+ if (st->st_openstp == NULL /* it's an open */ &&
+ access_permit_write(st) &&
+ st->st_stid.sc_client != clp) {
+ spin_unlock(&fp->fi_lock);
+ return -EAGAIN;
+ }
+ }
+ spin_unlock(&fp->fi_lock);
+ /*
+ * There's a small chance that we could be racing with another
+ * NFSv4 open. However, any open that hasn't added itself to
+ * the fi_stateids list also hasn't called break_lease yet; so,
+ * they'll break this lease soon enough.
+ */
+ return 0;
+}
+
static struct nfs4_delegation *
nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh,
struct nfs4_file *fp, struct nfs4_clnt_odstate *odstate)
@@ -4995,9 +5054,12 @@ nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh,
nf = find_readable_file(fp);
if (!nf) {
- /* We should always have a readable file here */
- WARN_ON_ONCE(1);
- return ERR_PTR(-EBADF);
+ /*
+ * 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);
}
spin_lock(&state_lock);
spin_lock(&fp->fi_lock);
@@ -5032,6 +5094,9 @@ nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh,
locks_free_lock(fl);
if (status)
goto out_clnt_odstate;
+ status = nfsd4_check_conflicting_opens(clp, fp);
+ if (status)
+ goto out_unlock;
spin_lock(&state_lock);
spin_lock(&fp->fi_lock);
@@ -5113,17 +5178,6 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open,
goto out_no_deleg;
if (!cb_up || !(oo->oo_flags & NFS4_OO_CONFIRMED))
goto out_no_deleg;
- /*
- * Also, if the file was opened for write or
- * create, there's a good chance the client's
- * about to write to it, resulting in an
- * immediate recall (since we don't support
- * write delegations):
- */
- if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE)
- goto out_no_deleg;
- if (open->op_create == NFS4_OPEN_CREATE)
- goto out_no_deleg;
break;
default:
goto out_no_deleg;
--
2.30.2
