Commit 1de94b52 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

eventfs: Shortcut eventfs_iterate() by skipping entries already read 

As the ei->entries array is fixed for the duration of the eventfs_inode,
it can be used to skip over already read entries in eventfs_iterate().

That is, if ctx->pos is greater than zero, there's no reason in doing the
loop across the ei->entries array for the entries less than ctx->pos.
Instead, start the lookup of the entries at the current ctx->pos.

Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.494956957@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: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 704f960d

fs/tracefs/event_inode.c

+10 −13
Original line number Diff line number Diff line
@@ -746,21 +746,15 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) 
	if (!ei || !ei_dentry)

		goto out;



	ret = 0;



	/*

	 * Need to create the dentries and inodes to have a consistent

	 * inode number.

	 */

	for (i = 0; i < ei->nr_entries; i++) {

		void *cdata = ei->data;



		if (c > 0) {

			c--;

			continue;

		}

	ret = 0;



		ctx->pos++;

	/* Start at 'c' to jump over already read entries */

	for (i = c; i < ei->nr_entries; i++, ctx->pos++) {

		void *cdata = ei->data;



		entry = &ei->entries[i];

		name = entry->name;
@@ -769,7 +763,7 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) 
		/* If ei->is_freed then just bail here, nothing more to do */

		if (ei->is_freed) {

			mutex_unlock(&eventfs_mutex);

			goto out_dec;

			goto out;

		}

		r = entry->callback(name, &mode, &cdata, &fops);

		mutex_unlock(&eventfs_mutex);
@@ -778,14 +772,17 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) 


		dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);

		if (!dentry)

			goto out_dec;

			goto out;

		ino = dentry->d_inode->i_ino;

		dput(dentry);



		if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))

			goto out_dec;

			goto out;

	}



	/* Subtract the skipped entries above */

	c -= min((unsigned int)c, (unsigned int)ei->nr_entries);



	list_for_each_entry_srcu(ei_child, &ei->children, list,

				 srcu_read_lock_held(&eventfs_srcu)) {