146 lines
4.8 KiB
Diff
146 lines
4.8 KiB
Diff
From dfdd500a339804075900bd1af42e433cf8d8f632 Mon Sep 17 00:00:00 2001
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From: Karel Zak <kzak@redhat.com>
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Date: Wed, 3 Jan 2024 14:13:28 +0100
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Subject: libmount: introduce /run/mount/utab.event
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The mnt_monitor_...() API uses /run/mount/utab.lock to monitor utab
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changes. The same file is used to control access to the utab file.
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The utab can be updated more than once during one mount(8) call, for
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example, one update is done in /sbin/mount.nfs and next in mount(8).
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This situation triggers two (e.g. inotify) events when monitoring is
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based on the lock file.
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It seems better to introduce separate file to trigger the event and do
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not trigger this event in /sbin/mount.<type> helpers.
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Addresses: https://issues.redhat.com/browse/RHEL-14612
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Upstream: http://github.com/util-linux/util-linux/commit/544824929a740ed5f8108c752872c7f082f301cf
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References: 477401f0de404aafbc7630f70c2f8b1d670e32f8
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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libmount/src/context.c | 6 ++++--
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libmount/src/monitor.c | 16 +++++++---------
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libmount/src/mountP.h | 1 +
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libmount/src/tab_update.c | 19 +++++++++++++++++++
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4 files changed, 31 insertions(+), 11 deletions(-)
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diff --git a/libmount/src/context.c b/libmount/src/context.c
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index 71b8d730a..c03b0ea64 100644
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--- a/libmount/src/context.c
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+++ b/libmount/src/context.c
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@@ -2293,7 +2293,7 @@ int mnt_context_update_tabs(struct libmnt_context *cxt)
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if (mnt_update_already_done(cxt->update, cxt->lock)) {
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DBG(CXT, ul_debugobj(cxt, "don't update: error evaluate or already updated"));
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- goto end;
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+ goto emit;
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}
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} else if (cxt->helper) {
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DBG(CXT, ul_debugobj(cxt, "don't update: external helper"));
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@@ -2317,7 +2317,9 @@ int mnt_context_update_tabs(struct libmnt_context *cxt)
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cxt->mountflags & MS_RDONLY);
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rc = mnt_update_table(cxt->update, cxt->lock);
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-
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+emit:
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+ if (rc == 0 && !mnt_context_within_helper(cxt))
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+ mnt_update_emit_event(cxt->update);
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end:
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if (!mnt_context_switch_ns(cxt, ns_old))
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return -MNT_ERR_NAMESPACE;
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diff --git a/libmount/src/monitor.c b/libmount/src/monitor.c
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index dada02ed3..4db56c2e0 100644
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--- a/libmount/src/monitor.c
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+++ b/libmount/src/monitor.c
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@@ -224,18 +224,16 @@ static int userspace_add_watch(struct monitor_entry *me, int *final, int *fd)
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assert(me->path);
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/*
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- * libmount uses rename(2) to atomically update utab, monitor
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- * rename changes is too tricky. It seems better to monitor utab
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- * lockfile close.
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+ * libmount uses utab.event file to monitor and control utab updates
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*/
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- if (asprintf(&filename, "%s.lock", me->path) <= 0) {
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+ if (asprintf(&filename, "%s.event", me->path) <= 0) {
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rc = -errno;
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goto done;
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}
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- /* try lock file if already exists */
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+ /* try event file if already exists */
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errno = 0;
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- wd = inotify_add_watch(me->fd, filename, IN_CLOSE_NOWRITE);
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+ wd = inotify_add_watch(me->fd, filename, IN_CLOSE_WRITE);
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if (wd >= 0) {
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DBG(MONITOR, ul_debug(" added inotify watch for %s [fd=%d]", filename, wd));
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rc = 0;
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@@ -254,7 +252,7 @@ static int userspace_add_watch(struct monitor_entry *me, int *final, int *fd)
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if (!*filename)
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break;
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- /* try directory where is the lock file */
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+ /* try directory where is the event file */
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errno = 0;
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wd = inotify_add_watch(me->fd, filename, IN_CREATE|IN_ISDIR);
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if (wd >= 0) {
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@@ -337,10 +335,10 @@ static int userspace_event_verify(struct libmnt_monitor *mn,
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e = (const struct inotify_event *) p;
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DBG(MONITOR, ul_debugobj(mn, " inotify event 0x%x [%s]\n", e->mask, e->len ? e->name : ""));
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- if (e->mask & IN_CLOSE_NOWRITE)
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+ if (e->mask & IN_CLOSE_WRITE)
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status = 1;
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else {
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- /* event on lock file */
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+ /* add watch for the event file */
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userspace_add_watch(me, &status, &fd);
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if (fd != e->wd) {
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diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
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index 4b4c5de1e..99b913c99 100644
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--- a/libmount/src/mountP.h
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+++ b/libmount/src/mountP.h
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@@ -476,6 +476,7 @@ extern int mnt_context_deferred_delete_veritydev(struct libmnt_context *cxt);
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/* tab_update.c */
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extern int mnt_update_set_filename(struct libmnt_update *upd,
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const char *filename, int userspace_only);
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+extern int mnt_update_emit_event(struct libmnt_update *upd);
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extern int mnt_update_already_done(struct libmnt_update *upd,
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struct libmnt_lock *lc);
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diff --git a/libmount/src/tab_update.c b/libmount/src/tab_update.c
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index f60f522ce..5ae369b74 100644
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--- a/libmount/src/tab_update.c
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+++ b/libmount/src/tab_update.c
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@@ -1003,6 +1003,25 @@ done:
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return rc;
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}
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+int mnt_update_emit_event(struct libmnt_update *upd)
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+{
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+ char *filename;
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+ int fd;
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+
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+ if (!upd || !upd->filename)
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+ return -EINVAL;
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+
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+ if (asprintf(&filename, "%s.event", upd->filename) <= 0)
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+ return -errno;
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+
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+ fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC,
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+ S_IWUSR|S_IRUSR|S_IRGRP|S_IROTH);
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+ free(filename);
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+ if (fd < 0)
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+ return -errno;
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+ close(fd);
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+ return 0;
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+}
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#ifdef TEST_PROGRAM
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--
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2.43.0
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