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Message-ID: <a40089cd2c7d492859dec6a7ef134d8f68aa761d.camel@poochiereds.net>
Subject: usage of inotify in nfs-utils
From: Jeff Layton <jlayton@poochiereds.net>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org
Date: Thu, 16 May 2024 07:17:08 -0600
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Al was asking about inotify usage in the rpc_pipefs dir.  If you want
to check further, all the binaries that operate under there are in
nfs-utils:

     http://git.linux-nfs.org/?p=3Dsteved/nfs-utils.git;a=3Dsummary

I took a quick look, and cscope shows these watches being added (with a
little annotation):

mountd and exportd watch creates and deletes in the nfsdfs clients dir:

    0 support/export/v4clients.c        40 if (inotify_add_watch(clients_fd=
, "/proc/fs/nfsd/clients", IN_CREATE | IN_DELETE) < 0) {

...if one of those directories is created, it watches for modifications
to the "info" file in there:

    1 support/export/v4clients.c	   117 key->wid =3D inotify_add_watch(clie=
nts_fd, path, IN_MODIFY);

...blkmapd watches for directories to show up in rpc_pipefs and in the
"nfs" directory below that:

    2 utils/blkmapd/device-discovery.c 358 *wd =3D inotify_add_watch(bl_wat=
ch_fd, dir, IN_CREATE|IN_DELETE);

...gssd has a pretty complex set of watches. There is a comment at the
top of gssd.c that explains them, but it watches for directories to
show up under rpc_pipefs, and then sets watches on the files under
those dirs (I think):

    3 utils/gssd/gssd.c                656 clp->wd =3D inotify_add_watch(in=
otify_fd, clp->relpath, IN_CREATE | IN_DELETE);
    4 utils/gssd/gssd.c                765 tdi->wd =3D inotify_add_watch(in=
otify_fd, name, IN_CREATE);

idmapd watches for dirs to show up in rpc_pipefs/nfs, and then watches
for directories under that to be created:

    5 utils/idmapd/idmapd.c            410 wd =3D inotify_add_watch(inotify=
_fd, pipefsdir, IN_CREATE | IN_DELETE);
    6 utils/idmapd/idmapd.c            930 inotify_add_watch(inotify_fd, ic=
->ic_path, IN_CREATE | IN_ONLYDIR | IN_ONESHOT);

nfsdcld watches for entries to show up in rpc_pipefs/nfsd/cld:

    7 utils/nfsdcld/nfsdcld.c          276 ret =3D inotify_add_watch(inotif=
y_fd, dname, IN_CREATE);

Al, Let me know if you have more questions, but it may be simpler to
just look in the nfs-utils tree.

Cheers,
--=20
Jeff Layton <jlayton@poochiereds.net>