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authorJ. Bruce Fields <bfields@redhat.com>2021-04-16 14:00:18 -0400
committerChuck Lever <chuck.lever@oracle.com>2021-04-19 16:41:36 -0400
commitaba2072f452346d56a462718bcde93d697383148 (patch)
treec42db8d613b8d0bf8d5de6717c5cd61225e9b506 /fs/nfsd
parentebd9d2c2f5a7ebaaed2d7bb4dee148755f46033d (diff)
nfsd: grant read delegations to clients holding writes
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 commit 94415b06eb8a ("nfsd4: a client's own opens needn't prevent delegations"), which had to be reverted in commit 6ee65a773096 ("Revert "nfsd4: a client's own opens needn't prevent delegations""). Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'fs/nfsd')
-rw-r--r--fs/nfsd/nfs4state.c82
1 files changed, 68 insertions, 14 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 94cb5f02f4b5..7364af580d83 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4988,6 +4988,65 @@ 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)
@@ -5007,9 +5066,12 @@ 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);
@@ -5044,6 +5106,9 @@ 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);
@@ -5125,17 +5190,6 @@ 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;