The patch titled Subject: eventfd: present id to userspace via fdinfo has been removed from the -mm tree. Its filename was eventfd-prepare-id-to-userspace-via-fdinfo.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Masatake YAMATO <yamato@xxxxxxxxxx> Subject: eventfd: present id to userspace via fdinfo 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 /proc/PID/fdinfo of eventfd as identifier. Integers managed by an IDA are used as ids. A tool like lsof can utilize the information to print endpoints. Link: http://lkml.kernel.org/r/20190327181823.20222-1-yamato@xxxxxxxxxx Signed-off-by: Masatake YAMATO <yamato@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/eventfd.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/fs/eventfd.c~eventfd-prepare-id-to-userspace-via-fdinfo +++ a/fs/eventfd.c @@ -21,6 +21,9 @@ #include <linux/eventfd.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> +#include <linux/idr.h> + +DEFINE_IDA(eventfd_ida); struct eventfd_ctx { struct kref kref; @@ -35,6 +38,7 @@ struct eventfd_ctx { */ __u64 count; unsigned int flags; + int id; }; /** @@ -69,6 +73,8 @@ 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); } @@ -297,6 +303,7 @@ static void eventfd_show_fdinfo(struct s seq_printf(m, "eventfd-count: %16llx\n", (unsigned long long)ctx->count); spin_unlock_irq(&ctx->wqh.lock); + seq_printf(m, "eventfd-id: %d\n", ctx->id); } #endif @@ -400,6 +407,7 @@ static int do_eventfd(unsigned int count 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, O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS)); _ Patches currently in -mm which might be from yamato@xxxxxxxxxx are