From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.hallyn.com ([178.63.66.53]:60320 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726269AbeLKXJQ (ORCPT ); Tue, 11 Dec 2018 18:09:16 -0500 Date: Tue, 11 Dec 2018 17:09:14 -0600 From: "Serge E. Hallyn" To: Masatake YAMATO Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH resend] eventfd: make eventfd files distinguishable in /proc/$PID/fd Message-ID: <20181211230914.GA2677@mail.hallyn.com> References: <20181209183546.5550-1-yamato@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181209183546.5550-1-yamato@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Dec 10, 2018 at 03:35:46AM +0900, Masatake YAMATO wrote: > Finding endpoints of an IPC channel is one of essential task to > understand how a user program works. Procfs and netlink socket provide > enough hints to find endpoints for IPC channels like pipes, unix > sockets, and pseudo terminals. However, there is no simple way to find > endpoints for an eventfd file from userland. An inode number doesn't > hint. Unlike pipe, all eventfd files shares one inode object. > > To provide the way to find endpoints of an eventfd file, this patch > adds eventfd identifiers to the output of 'ls -l /proc/$pid/fd' like: > > ... > lrwx------. 1 qemu qemu 64 May 20 04:49 93 -> 'anon_inode:[eventfd:130]' > lrwx------. 1 qemu qemu 64 May 20 04:49 94 -> 'anon_inode:[eventfd:131]' > ... > > Here "130" and "131" are added as identifiers newly added. > In the case that ida_simple_get returns an error, this change doesn't add > an identifier; just use "[eventfd]" as before. > > Signed-off-by: Masatake YAMATO I'm going to love this when I need it :) Thanks. Acked-by: Serge Hallyn > --- > fs/eventfd.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/eventfd.c b/fs/eventfd.c > index 08d3bd602f73..c18952948110 100644 > --- a/fs/eventfd.c > +++ b/fs/eventfd.c > @@ -21,6 +21,11 @@ > #include > #include > #include > +#include > + > +/* Worst case buffer size needed for holding an integer. */ > +#define ITOA_MAX_LEN 12 > +DEFINE_IDA(eventfd_ida); > > struct eventfd_ctx { > struct kref kref; > @@ -35,6 +40,7 @@ struct eventfd_ctx { > */ > __u64 count; > unsigned int flags; > + int id; > }; > > /** > @@ -69,6 +75,8 @@ EXPORT_SYMBOL_GPL(eventfd_signal); > > static void eventfd_free_ctx(struct eventfd_ctx *ctx) > { > + if (ctx->id >= 0) > + ida_simple_remove(&eventfd_ida, ctx->id); > kfree(ctx); > } > > @@ -384,6 +392,7 @@ static int do_eventfd(unsigned int count, int flags) > { > struct eventfd_ctx *ctx; > int fd; > + char name[1 + 8 + ITOA_MAX_LEN + 1 + 1] = "[eventfd]"; > > /* Check the EFD_* constants for consistency. */ > BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); > @@ -400,8 +409,11 @@ static int do_eventfd(unsigned int count, int flags) > init_waitqueue_head(&ctx->wqh); > ctx->count = count; > ctx->flags = flags; > + ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL); > > - fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx, > + if (ctx->id >= 0) > + snprintf(name, sizeof(name), "[eventfd:%d]", ctx->id); > + fd = anon_inode_getfd(name, &eventfd_fops, ctx, > O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS)); > if (fd < 0) > eventfd_free_ctx(ctx); > -- > 2.17.0