On Tue, 11 Dec 2018 17:09:14 -0600, "Serge E. Hallyn" <serge@xxxxxxxxxx> wrote:
> 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 <yamato@xxxxxxxxxx>
>
> I'm going to love this when I need it :) Thanks.
>
> Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
>
Thank you for replying.
This is the first time getting replying since my first post,
Mon, 21 May 2018 05:18:23 +0900.
Can I expect my patch is merged to the mainline?
Or should I do something more?
Masatake YAMATO
>> ---
>> 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 <linux/eventfd.h>
>> #include <linux/proc_fs.h>
>> #include <linux/seq_file.h>
>> +#include <linux/idr.h>
>> +
>> +/* 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
