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From:   Stephen Brennan <stephen.s.brennan@oracle.com>
To:     Jan Kara <jack@suse.cz>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Al Viro <viro@zeniv.linux.org.uk>,
        Stephen Brennan <stephen.s.brennan@oracle.com>,
        Amir Goldstein <amir73il@gmail.com>
Subject: [PATCH v4 3/5] dnotify: move fsnotify_recalc_mask() outside spinlock
Date:   Fri, 11 Nov 2022 14:06:12 -0800
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In order to allow sleeping during fsnotify_recalc_mask(), we need to
ensure no callers are holding a spinlock.

Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
 fs/notify/dnotify/dnotify.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 190aa717fa32..a9f05b3cf5ea 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -58,10 +58,10 @@ struct dnotify_mark {
  * dnotify cares about for that inode may change.  This function runs the
  * list of everything receiving dnotify events about this directory and calculates
  * the set of all those events.  After it updates what dnotify is interested in
- * it calls the fsnotify function so it can update the set of all events relevant
- * to this inode.
+ * it returns true if fsnotify_recalc_mask() should be called to update the set
+ * of all events related to this inode.
  */
-static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
+static bool dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
 {
 	__u32 new_mask = 0;
 	struct dnotify_struct *dn;
@@ -74,10 +74,9 @@ static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
 	for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
 		new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
 	if (fsn_mark->mask == new_mask)
-		return;
+		return false;
 	fsn_mark->mask = new_mask;
-
-	fsnotify_recalc_mask(fsn_mark->connector);
+	return true;
 }
 
 /*
@@ -97,6 +96,7 @@ static int dnotify_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
 	struct dnotify_struct **prev;
 	struct fown_struct *fown;
 	__u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
+	bool recalc = false;
 
 	/* not a dir, dnotify doesn't care */
 	if (!dir && !(mask & FS_ISDIR))
@@ -118,12 +118,15 @@ static int dnotify_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
 		else {
 			*prev = dn->dn_next;
 			kmem_cache_free(dnotify_struct_cache, dn);
-			dnotify_recalc_inode_mask(inode_mark);
+			recalc = dnotify_recalc_inode_mask(inode_mark);
 		}
 	}
 
 	spin_unlock(&inode_mark->lock);
 
+	if (recalc)
+		fsnotify_recalc_mask(inode_mark->connector);
+
 	return 0;
 }
 
@@ -158,6 +161,7 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 	struct dnotify_struct **prev;
 	struct inode *inode;
 	bool free = false;
+	bool recalc = false;
 
 	inode = file_inode(filp);
 	if (!S_ISDIR(inode->i_mode))
@@ -176,7 +180,7 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 		if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
 			*prev = dn->dn_next;
 			kmem_cache_free(dnotify_struct_cache, dn);
-			dnotify_recalc_inode_mask(fsn_mark);
+			recalc = dnotify_recalc_inode_mask(fsn_mark);
 			break;
 		}
 		prev = &dn->dn_next;
@@ -184,6 +188,9 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 
 	spin_unlock(&fsn_mark->lock);
 
+	if (recalc)
+		fsnotify_recalc_mask(fsn_mark->connector);
+
 	/* nothing else could have found us thanks to the dnotify_groups
 	   mark_mutex */
 	if (dn_mark->dn == NULL) {
@@ -268,6 +275,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
 	struct file *f;
 	int destroy = 0, error = 0;
 	__u32 mask;
+	bool recalc = false;
 
 	/* we use these to tell if we need to kfree */
 	new_fsn_mark = NULL;
@@ -377,9 +385,11 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
 	else if (error == -EEXIST)
 		error = 0;
 
-	dnotify_recalc_inode_mask(fsn_mark);
+	recalc = dnotify_recalc_inode_mask(fsn_mark);
 out:
 	spin_unlock(&fsn_mark->lock);
+	if (recalc)
+		fsnotify_recalc_mask(fsn_mark->connector);
 
 	if (destroy)
 		fsnotify_detach_mark(fsn_mark);
-- 
2.34.1