[PATCH v6 05/20] nfsd: update the fsnotify mark when setting or removing a dir delegation

[Jeff Layton <jlayton@kernel.org>]

Add a new helper function that will update the mask on the nfsd_file's
fsnotify_mark to be a union of all current directory delegations on an
inode.

Call that when directory delegations are added or removed, since that
can change what fsnotify events nfsd requires from the VFS layer.

The fsnotify_mark is shared by every nfsd_file open on the inode, so
concurrent delegation adds and removes on the same directory can run
nfsd_fsnotify_recalc_mask() in parallel. Because it reads the lease
state and updates the mark in two separate locked sections, a recalc
working from a stale snapshot of the lease list could clobber a
concurrent update and leave the mark missing required events. Add an
nfm_recalc_mutex to the nfsd_file_mark and hold it across the recalc to
serialize callers.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/filecache.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/nfsd/filecache.h |  3 +++
 fs/nfsd/nfs4state.c |  5 +++--
 3 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 1ea2bfd51825..c5f2c5768324 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -192,6 +192,7 @@ nfsd_file_mark_find_or_create(struct inode *inode)
 		fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
 		new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;
 		refcount_set(&new->nfm_ref, 1);
+		mutex_init(&new->nfm_recalc_mutex);
 
 		err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
 
@@ -1473,3 +1474,54 @@ int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 		seq_printf(m, "mean age (ms): -\n");
 	return 0;
 }
+
+/**
+ * nfsd_fsnotify_recalc_mask - recalculate the fsnotify mask for a nfsd_file
+ * @nf: nfsd_file to recalculate the mask on
+ *
+ * When a directory nfsd_file has a delegation added or removed, that may
+ * change the events that nfsd requires from the VFS layer. This function
+ * recalculates the fsnotify mask based on the leases present.
+ */
+void nfsd_fsnotify_recalc_mask(struct nfsd_file *nf)
+{
+	struct inode *inode = file_inode(nf->nf_file);
+	u32 lease_mask, set = 0, clear = 0;
+	struct fsnotify_mark *mark;
+
+	/* This is only needed when adding or removing dir delegs */
+	if (!S_ISDIR(inode->i_mode) || !nf->nf_mark)
+		return;
+
+	mark = &nf->nf_mark->nfm_mark;
+
+	/*
+	 * The mark is shared by every nfsd_file on this inode, so concurrent
+	 * delegation add/remove on the same directory can recalc it in
+	 * parallel. Serialize the read of the lease state and the update of
+	 * the mark so that a recalc working from a stale snapshot of the
+	 * lease list can't clobber a concurrent recalc's update.
+	 */
+	mutex_lock(&nf->nf_mark->nfm_recalc_mutex);
+
+	/* Set up notifications for any ignored delegation events */
+	lease_mask = inode_lease_ignore_mask(inode);
+
+	if (lease_mask & FL_IGN_DIR_CREATE)
+		set |= FS_CREATE | FS_MOVED_TO;
+	else
+		clear |= FS_CREATE | FS_MOVED_TO;
+
+	if (lease_mask & FL_IGN_DIR_DELETE)
+		set |= FS_DELETE | FS_MOVED_FROM;
+	else
+		clear |= FS_DELETE | FS_MOVED_FROM;
+
+	if (lease_mask & FL_IGN_DIR_RENAME)
+		set |= FS_RENAME;
+	else
+		clear |= FS_RENAME;
+
+	fsnotify_modify_mark_mask(mark, set, clear);
+	mutex_unlock(&nf->nf_mark->nfm_recalc_mutex);
+}
diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index 683b6437cacc..b224902b438d 100644
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -26,6 +26,8 @@
 struct nfsd_file_mark {
 	struct fsnotify_mark	nfm_mark;
 	refcount_t		nfm_ref;
+	/* serializes nfsd_fsnotify_recalc_mask() against itself */
+	struct mutex		nfm_recalc_mutex;
 };
 
 /*
@@ -86,4 +88,5 @@ __be32 nfsd_file_acquire_local(struct net *net, struct svc_cred *cred,
 __be32 nfsd_file_acquire_dir(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		  struct nfsd_file **pnf);
 int nfsd_file_cache_stats_show(struct seq_file *m, void *v);
+void nfsd_fsnotify_recalc_mask(struct nfsd_file *nf);
 #endif /* _FS_NFSD_FILECACHE_H */
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ae8505747dc2..0cbb37f73ee7 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1255,6 +1255,7 @@ static void nfs4_unlock_deleg_lease(struct nfs4_delegation *dp)
 
 	nfsd4_finalize_deleg_timestamps(dp, nf->nf_file);
 	kernel_setlease(nf->nf_file, F_UNLCK, NULL, (void **)&dp);
+	nfsd_fsnotify_recalc_mask(nf);
 	put_deleg_file(fp);
 }
 
@@ -9725,8 +9726,7 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
  * @nf: nfsd_file opened on the directory
  *
  * Given a GET_DIR_DELEGATION request @gdd, attempt to acquire a delegation
- * on the directory to which @nf refers. Note that this does not set up any
- * sort of async notifications for the delegation.
+ * on the directory to which @nf refers.
  */
 struct nfs4_delegation *
 nfsd_get_dir_deleg(struct nfsd4_compound_state *cstate,
@@ -9816,6 +9816,7 @@ nfsd_get_dir_deleg(struct nfsd4_compound_state *cstate,
 
 	if (!status) {
 		put_nfs4_file(fp);
+		nfsd_fsnotify_recalc_mask(nf);
 		return dp;
 	}
 

-- 
2.54.0