From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B3BA34B669 for ; Tue, 7 Apr 2026 19:51:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775591484; cv=none; b=eBUdGRrOu4t8YXvoOU0HxinvNQetn/hPN86cUNDor1dzc1hXFvJkdFHOwCDM+1hWhEyRBqcYI4JIyG2NlMSmgYQzWurWPyeuhRZTcOoniJwq/AoNzJ4zy4ABTkSq/nD/X2AkEOe/AG4BhdKMK9q27H6bz+j8EkIFFuDh6E7C/W8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775591484; c=relaxed/simple; bh=jF+dvC9/Bf9gqz2e5K9Hw8USL10XFvJV0PzK2as4dfY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=hYJShjIhCfhqWLeZisQIp6U+PC4DMUtjjnYIopQ7R78U+nj0q3t9WzCtVCWO7qlAcSjvr537ImuhLIpA48bun8fEs9XEuCetNk+YeCoSJ6iecIJF5Cg8GO2iKWIXQaMu+egYy5TI0PjenUGoz27GVF6ojbKXC2oAQ8A76I7MZx0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G5CMzUI6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="G5CMzUI6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27FD5C116C6; Tue, 7 Apr 2026 19:51:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775591483; bh=jF+dvC9/Bf9gqz2e5K9Hw8USL10XFvJV0PzK2as4dfY=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=G5CMzUI6vMlZCYw+6w3s9pQDwLZlQhy/nBgsmpRffLIknuLaKkXnMsK6YDR13Gyka eFqPGJ8yWIo73jflXX6IqNf3K6MXbUvsJ0/QltmRYhH8LorMmg+U1L5yNX1+beoOcD uqdShJw2bFtNSkD2faLn8SMkmqIhaWRoIva9Pc+/7y1ZHVyKe7hF9bYGiDeya8RmAU Jv4oAXie++eeHJIpOdj7kgzlvchm6gcvKUSlBzN1QWRaBhALsfgLe1LHiuvl33+iD5 RUX0gFWe0ZBhEdpCJ1Yce4dVIv9YoeNvBihrSc/3mnW/0K5VJIgb4V1/OPZ6pQE7yH v0So+iJVRtRCA== Message-ID: <1949725ad3cebae2f38aa7cceed218f974b9f8a4.camel@kernel.org> Subject: Re: [PATCH v2] exportfs: release NFSv4 state when last client is unexported From: Jeff Layton To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever Date: Tue, 07 Apr 2026 15:51:20 -0400 In-Reply-To: <20260406172653.1962-1-cel@kernel.org> References: <20260406172653.1962-1-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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When exportfs -u removes the last client for a given export path, > NFSv4 state (opens, locks, delegations) acquired through that > export may still hold the underlying filesystem busy, preventing > unmount. >=20 > After removing an export entry, check whether any active exports > remain for the same path across all client types. If none remain, > send NFSD_CMD_UNLOCK_EXPORT to the kernel via generic netlink, > which revokes the associated NFSv4 state and closes cached file > handles. >=20 > This uses a new shared helper, nfsd_nl_cmd_str(), in > support/nfs/nfsdnl.c that handles the netlink socket setup, message > construction, and ACK handling for simple nfsd commands carrying > a single string attribute. The helper is conditionally compiled > when libnl3 is available (gated by the existing nfsdctl configure > option). >=20 > Also update the local nfsd_netlink.h copy with the > NFSD_CMD_UNLOCK_IP, NFSD_CMD_UNLOCK_FILESYSTEM, and > NFSD_CMD_UNLOCK_EXPORT command and attribute definitions. >=20 > Signed-off-by: Chuck Lever > --- > configure.ac | 2 + > support/include/nfsd_netlink.h | 24 +++++++ > support/include/nfsdnl.h | 34 +++++++++ > support/nfs/Makefile.am | 7 ++ > support/nfs/nfsdnl.c | 124 +++++++++++++++++++++++++++++++++ > utils/exportfs/exportfs.c | 65 ++++++++++++++++- > utils/exportfs/exportfs.man | 17 +++++ > 7 files changed, 271 insertions(+), 2 deletions(-) > create mode 100644 support/include/nfsdnl.h > create mode 100644 support/nfs/nfsdnl.c >=20 > diff --git a/configure.ac b/configure.ac > index 115c611fa5e3..8ca06fd62b47 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -256,6 +256,8 @@ PKG_CHECK_MODULES(LIBNL3, libnl-3.0 >=3D 3.1) > PKG_CHECK_MODULES(LIBNLGENL3, libnl-genl-3.0 >=3D 3.1) > =20 > AC_CHECK_HEADERS(linux/nfsd_netlink.h) > +AC_DEFINE([HAVE_NFSD_NETLINK], 1, > + [Define to 1 if nfsd generic netlink support is available]) > =20 > # ensure we have the expkey attributes > AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include ]], > diff --git a/support/include/nfsd_netlink.h b/support/include/nfsd_netlin= k.h > index 2d708d24cbd2..a6a831866be8 100644 > --- a/support/include/nfsd_netlink.h > +++ b/support/include/nfsd_netlink.h > @@ -128,6 +128,27 @@ enum { > NFSD_A_POOL_MODE_MAX =3D (__NFSD_A_POOL_MODE_MAX - 1) > }; > =20 > +enum { > + NFSD_A_UNLOCK_IP_ADDRESS =3D 1, > + > + __NFSD_A_UNLOCK_IP_MAX, > + NFSD_A_UNLOCK_IP_MAX =3D (__NFSD_A_UNLOCK_IP_MAX - 1) > +}; > + > +enum { > + NFSD_A_UNLOCK_FILESYSTEM_PATH =3D 1, > + > + __NFSD_A_UNLOCK_FILESYSTEM_MAX, > + NFSD_A_UNLOCK_FILESYSTEM_MAX =3D (__NFSD_A_UNLOCK_FILESYSTEM_MAX - 1) > +}; > + > +enum { > + NFSD_A_UNLOCK_EXPORT_PATH =3D 1, > + > + __NFSD_A_UNLOCK_EXPORT_MAX, > + NFSD_A_UNLOCK_EXPORT_MAX =3D (__NFSD_A_UNLOCK_EXPORT_MAX - 1) > +}; > + > enum { > NFSD_A_FSLOCATION_HOST =3D 1, > NFSD_A_FSLOCATION_PATH, > @@ -229,6 +250,9 @@ enum { > NFSD_CMD_EXPKEY_GET_REQS, > NFSD_CMD_EXPKEY_SET_REQS, > NFSD_CMD_CACHE_FLUSH, > + NFSD_CMD_UNLOCK_IP, > + NFSD_CMD_UNLOCK_FILESYSTEM, > + NFSD_CMD_UNLOCK_EXPORT, > =20 > __NFSD_CMD_MAX, > NFSD_CMD_MAX =3D (__NFSD_CMD_MAX - 1) > diff --git a/support/include/nfsdnl.h b/support/include/nfsdnl.h > new file mode 100644 > index 000000000000..352801e5cc43 > --- /dev/null > +++ b/support/include/nfsdnl.h > @@ -0,0 +1,34 @@ > +/* > + * Helper for sending nfsd generic netlink commands. > + * > + * Used by both nfsdctl and exportfs. > + */ > + > +#ifndef NFS_UTILS_NFSDNL_H > +#define NFS_UTILS_NFSDNL_H > + > +#ifdef HAVE_NFSD_NETLINK > + > +/** > + * nfsd_nl_cmd_str - send an nfsd netlink command carrying a string attr= ibute > + * @cmd: NFSD_CMD_* command number > + * @attr: NFSD_A_* attribute number > + * @value: NUL-terminated string value for the attribute > + * > + * Opens a genetlink connection, resolves the "nfsd" family, sends a > + * single "do" command with one string attribute, waits for the ACK, > + * and cleans up. > + * > + * Returns 0 on success or a negative errno on failure. > + */ > +int nfsd_nl_cmd_str(int cmd, int attr, const char *value); > + > +#else > + > +static inline int nfsd_nl_cmd_str(int cmd, int attr, const char *value) > +{ > + return -ENOSYS; > +} > + > +#endif /* HAVE_NFSD_NETLINK */ > +#endif /* NFS_UTILS_NFSDNL_H */ > diff --git a/support/nfs/Makefile.am b/support/nfs/Makefile.am > index 5bfd71a9c8da..64ad5d075b9e 100644 > --- a/support/nfs/Makefile.am > +++ b/support/nfs/Makefile.am > @@ -11,6 +11,13 @@ libnfs_la_SOURCES =3D exports.c rmtab.c xio.c rpcmisc.= c rpcdispatch.c \ > libnfs_la_LIBADD =3D libnfsconf.la -luuid > libnfs_la_CPPFLAGS =3D $(AM_CPPFLAGS) $(CPPFLAGS) -I$(top_srcdir)/suppor= t/reexport > =20 > +if CONFIG_NFSDCTL > +libnfs_la_SOURCES +=3D nfsdnl.c > +libnfs_la_CPPFLAGS +=3D $(LIBNL3_CFLAGS) $(LIBNLGENL3_CFLAGS) \ > + -I$(top_srcdir)/utils/nfsdctl > +libnfs_la_LIBADD +=3D $(LIBNL3_LIBS) $(LIBNLGENL3_LIBS) > +endif > + > libnfsconf_la_SOURCES =3D conffile.c xlog.c > =20 > MAINTAINERCLEANFILES =3D Makefile.in > diff --git a/support/nfs/nfsdnl.c b/support/nfs/nfsdnl.c > new file mode 100644 > index 000000000000..ece0b57afd4b > --- /dev/null > +++ b/support/nfs/nfsdnl.c > @@ -0,0 +1,124 @@ > +/* > + * nfsdnl.c -- send nfsd generic netlink commands > + * > + * Helper shared by nfsdctl and exportfs. > + */ > + > +#ifdef HAVE_CONFIG_H > +#include > +#endif > + > +#include > +#include > + > +#include > +#include > +#include > +#include > + > +#include "xlog.h" > +#include "nfsdnl.h" > + > +#ifdef USE_SYSTEM_NFSD_NETLINK_H > +#include > +#else > +#include "nfsd_netlink.h" > +#endif > + > +#define NFSDNL_BUFSIZE (4096) > + > +static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr *err, > + void *arg) > +{ > + int *ret =3D arg; > + *ret =3D err->error; > + return NL_STOP; > +} > + > +static int finish_handler(struct nl_msg *msg, void *arg) > +{ > + int *ret =3D arg; > + *ret =3D 0; > + return NL_SKIP; > +} > + > +static int ack_handler(struct nl_msg *msg __attribute__((unused)), > + void *arg) > +{ > + int *ret =3D arg; > + *ret =3D 0; > + return NL_STOP; > +} > + > +/** > + * nfsd_nl_cmd_str - send an nfsd netlink command carrying a string attr= ibute > + * @cmd: NFSD_CMD_* command number > + * @attr: NFSD_A_* attribute number > + * @value: NUL-terminated string value for the attribute > + * > + * Returns 0 on success or a negative errno on failure. > + */ > +int nfsd_nl_cmd_str(int cmd, int attr, const char *value) > +{ > + struct genlmsghdr *ghdr; > + struct nl_sock *sock; > + struct nl_msg *msg; > + struct nl_cb *cb; > + int family; > + int ret; > + > + sock =3D nl_socket_alloc(); > + if (!sock) > + return -ENOMEM; > + if (genl_connect(sock)) { > + ret =3D -ECONNREFUSED; > + goto out_sock; > + } > + nl_socket_set_buffer_size(sock, NFSDNL_BUFSIZE, NFSDNL_BUFSIZE); > + > + family =3D genl_ctrl_resolve(sock, NFSD_FAMILY_NAME); > + if (family < 0) { > + ret =3D family; > + goto out_sock; > + } > + > + msg =3D nlmsg_alloc(); > + if (!msg) { > + ret =3D -ENOMEM; > + goto out_sock; > + } > + if (!genlmsg_put(msg, 0, 0, family, 0, 0, 0, 0)) { > + ret =3D -ENOMEM; > + goto out_msg; > + } > + > + ghdr =3D nlmsg_data(nlmsg_hdr(msg)); > + ghdr->cmd =3D (__u8)cmd; > + nla_put_string(msg, attr, value); > + > + cb =3D nl_cb_alloc(NL_CB_CUSTOM); > + if (!cb) { > + ret =3D -ENOMEM; > + goto out_msg; > + } > + > + ret =3D nl_send_auto(sock, msg); > + if (ret < 0) > + goto out_cb; > + > + ret =3D 1; > + nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &ret); > + nl_cb_set(cb, NL_CB_FINISH, NL_CB_CUSTOM, finish_handler, &ret); > + nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &ret); > + > + while (ret > 0) > + nl_recvmsgs(sock, cb); > + > +out_cb: > + nl_cb_put(cb); > +out_msg: > + nlmsg_free(msg); > +out_sock: > + nl_socket_free(sock); > + return ret; > +} > diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c > index 93f0bcd7ad56..768d2db7ea8f 100644 > --- a/utils/exportfs/exportfs.c > +++ b/utils/exportfs/exportfs.c > @@ -39,6 +39,15 @@ > #include "xlog.h" > #include "conffile.h" > #include "reexport.h" > +#include "nfsdnl.h" > + > +#ifdef HAVE_NFSD_NETLINK > +#ifdef USE_SYSTEM_NFSD_NETLINK_H > +#include > +#else > +#include "nfsd_netlink.h" > +#endif > +#endif > =20 > #include > #include > @@ -63,6 +72,7 @@ static void release_lockfile(void); > =20 > static const char *lockfile =3D EXP_LOCKFILE; > static int _lockfd =3D -1; > +static int f_unexport_all; > =20 > /* > * If we aren't careful, changes made by exportfs can be lost > @@ -246,7 +256,8 @@ main(int argc, char **argv) > * don't care about what should be exported, as that > * may require DNS lookups.. > */ > - if (! ( !f_export && f_all)) { > + f_unexport_all =3D !f_export && f_all; > + if (!f_unexport_all) { > /* note: xtab_*_read does not update entries if they already exist, > * so this will not lose new options > */ > @@ -380,6 +391,26 @@ exportfs(char *arg, char *options, int verbose) > xlog(L_ERROR, "Invalid export syntax: %s", arg); > } > =20 > +/* > + * Check whether any active export remains for the given path across > + * all client types. Returns true if at least one export still has > + * m_xtabent set. > + */ > +static int > +path_still_exported(const char *path, size_t nlen) > +{ > + nfs_export *exp; > + int i; > + > + for (i =3D 0; i < MCL_MAXTYPES; i++) > + for (exp =3D exportlist[i].p_head; exp; exp =3D exp->m_next) > + if (exp->m_xtabent && > + strlen(exp->m_export.e_path) =3D=3D nlen && > + strncmp(path, exp->m_export.e_path, nlen) =3D=3D 0) > + return 1; > + return 0; > +} > + > static void > unexportfs_parsed(char *hname, char *path, int verbose) > { > @@ -434,9 +465,39 @@ unexportfs_parsed(char *hname, char *path, int verbo= se) > exp->m_mayexport =3D 0; > success =3D 1; > } > - if (!success) > + if (!success) { > xlog(L_ERROR, "Could not find '%s:%s' to unexport.", hname, path); > + goto out; > + } > =20 > + /* > + * If no exports remain for this path, ask the kernel to > + * revoke any NFSv4 state and close cached file handles > + * associated with exports of this path. This enables the > + * underlying filesystem to be unmounted. > + * > + * Skip this during "exportfs -ua" -- that is a shutdown > + * operation. Clients should wait for nfsd to restart and > + * reclaim state through the grace period rather than > + * receiving NFS4ERR_ADMIN_REVOKED. > + */ > +#ifdef HAVE_NFSD_NETLINK I don't think you need this #ifdef. With the latest exportfs changes, netlink support is pretty much required to build. > + if (!f_unexport_all && !path_still_exported(path, nlen)) { > + char pathbuf[NFS_MAXPATHLEN + 1]; > + int ret; > + > + memcpy(pathbuf, path, nlen); > + pathbuf[nlen] =3D '\0'; > + ret =3D nfsd_nl_cmd_str(NFSD_CMD_UNLOCK_EXPORT, > + NFSD_A_UNLOCK_EXPORT_PATH, > + pathbuf); > + if (ret && ret !=3D -ENOSYS) > + xlog(L_WARNING, > + "Failed to release state for %s: %s", > + pathbuf, strerror(-ret)); > + } > +#endif > +out: > nfs_freeaddrinfo(ai); > } > =20 > diff --git a/utils/exportfs/exportfs.man b/utils/exportfs/exportfs.man > index 3737ee81ab27..b5e0c63a63f2 100644 > --- a/utils/exportfs/exportfs.man > +++ b/utils/exportfs/exportfs.man > @@ -256,6 +256,23 @@ pair. This deletes the specified entry from > .I /var/lib/nfs/etab > and removes the corresponding kernel entry (if any). > .PP > +When the last client for a given export path is unexported, > +.B exportfs > +signals the kernel to revoke NFSv4 state (opens, locks, and > +delegations) and release cached state for that path. > +Without this revocation, retained state would prevent the > +underlying filesystem from being unmounted. > +Affected clients receive > +.B NFS4ERR_ADMIN_REVOKED > +errors for operations that use revoked state. > +.PP > +.B "exportfs \-ua" > +does not revoke NFSv4 state, however. > +If > +.B nfsd > +is then restarted, clients may reclaim state during the > +grace period. > +.PP > .SS Dumping the Export Table > Invoking > .B exportfs The rest looks good. Reviewed-by: Jeff Layton