eventfs: Read ei->entries before ei->children in eventfs_iterate()

commit 704f960dbee2f1634f4b4e16f208cb16eaf41c1e upstream.

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@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index d4d48916dd834e83c0c62019e16681410b5f31d9..0a7ded12d4c0d4f1daf0374a240d64d31d97ad66 100644 (file)
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -714,8 +714,8 @@ 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--;
@@ -724,23 +724,32 @@ 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--;
@@ -749,27 +758,18 @@ 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;