Finding endpoints of an IPC channel is one of essential task to understand how a user program works. Procfs and netlink socket provide enough hints to find endpoints for IPC channels like pipes, unix sockets, and pseudo terminals. However, there is no simple way to find endpoints for an eventfd file from userland. An inode number doesn't hint. Unlike pipe, all eventfd files share the same inode object. To provide the way to find endpoints of an eventfd file, this patch adds "eventfd-id" field to fdinfo of eventfd as identifier. Address for eventfd context is used as id. Typical applicaiton utilizing the information is lsof. Signed-off-by: Masatake YAMATO <yamato@xxxxxxxxxx> --- fs/eventfd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/eventfd.c b/fs/eventfd.c index 08d3bd602f73..fc63ad43d962 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -297,6 +297,7 @@ static void eventfd_show_fdinfo(struct seq_file *m, struct file *f) seq_printf(m, "eventfd-count: %16llx\n", (unsigned long long)ctx->count); spin_unlock_irq(&ctx->wqh.lock); + seq_printf(m, "eventfd-id: %p\n", ctx); } #endif -- 2.17.2
