linux-kernel - [for-next][PATCH 3/4] eventfs: Read ei->entries before ei->children in eventfs

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Date: Fri, 05 Jan 2024 13:00:54 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Al Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [for-next][PATCH 3/4] eventfs: Read ei->entries before ei->children in eventfs_iterate()

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

In order to apply a shortcut to skip over the current ctx->pos
immediately, by using the ei->entries array, the reading of that array
should be first. Moving the array reading before the linked list reading
will make the shortcut change diff nicer to read.

Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.333115095@goodmis.org

Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 fs/tracefs/event_inode.c | 46 ++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index c73fb1f7ddbc..a1934e0eea3b 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -752,8 +752,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 	 * Need to create the dentries and inodes to have a consistent
 	 * inode number.
 	 */
-	list_for_each_entry_srcu(ei_child, &ei->children, list,
-				 srcu_read_lock_held(&eventfs_srcu)) {
+	for (i = 0; i < ei->nr_entries; i++) {
+		void *cdata = ei->data;
 
 		if (c > 0) {
 			c--;
@@ -762,23 +762,32 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 
 		ctx->pos++;
 
-		if (ei_child->is_freed)
-			continue;
+		entry = &ei->entries[i];
+		name = entry->name;
 
-		name = ei_child->name;
+		mutex_lock(&eventfs_mutex);
+		/* If ei->is_freed then just bail here, nothing more to do */
+		if (ei->is_freed) {
+			mutex_unlock(&eventfs_mutex);
+			goto out_dec;
+		}
+		r = entry->callback(name, &mode, &cdata, &fops);
+		mutex_unlock(&eventfs_mutex);
+		if (r <= 0)
+			continue;
 
-		dentry = create_dir_dentry(ei, ei_child, ei_dentry);
+		dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);
 		if (!dentry)
 			goto out_dec;
 		ino = dentry->d_inode->i_ino;
 		dput(dentry);
 
-		if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR))
+		if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
 			goto out_dec;
 	}
 
-	for (i = 0; i < ei->nr_entries; i++) {
-		void *cdata = ei->data;
+	list_for_each_entry_srcu(ei_child, &ei->children, list,
+				 srcu_read_lock_held(&eventfs_srcu)) {
 
 		if (c > 0) {
 			c--;
@@ -787,27 +796,18 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 
 		ctx->pos++;
 
-		entry = &ei->entries[i];
-		name = entry->name;
-
-		mutex_lock(&eventfs_mutex);
-		/* If ei->is_freed then just bail here, nothing more to do */
-		if (ei->is_freed) {
-			mutex_unlock(&eventfs_mutex);
-			goto out_dec;
-		}
-		r = entry->callback(name, &mode, &cdata, &fops);
-		mutex_unlock(&eventfs_mutex);
-		if (r <= 0)
+		if (ei_child->is_freed)
 			continue;
 
-		dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);
+		name = ei_child->name;
+
+		dentry = create_dir_dentry(ei, ei_child, ei_dentry);
 		if (!dentry)
 			goto out_dec;
 		ino = dentry->d_inode->i_ino;
 		dput(dentry);
 
-		if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
+		if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR))
 			goto out_dec;
 	}
 	ret = 1;
-- 
2.42.0