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From 6032a92b8fb27a7c65a1853e62a142fd9a062b73 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Thu, 17 Aug 2017 10:21:23 +0200
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Subject: [PATCH] journald: don't flush to /var/log/journal before we get asked
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 to
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This changes journald to not write to /var/log/journal until it received
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SIGUSR1 for the first time, thus having been requested to flush the runtime
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journal to disk.
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This makes the journal work nicer with systems which have the root file system
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writable early, but still need to rearrange /var before journald should start
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writing and creating files to it, for example because ACLs need to be applied
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first, or because /var is to be mounted from another file system, NFS or tmpfs
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(as is the case for systemd.volatile=state).
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Before this change we required setupts with /var split out to mount the root
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disk read-only early on, and ship an /etc/fstab that remounted it writable only
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after having placed /var at the right place. But even that was racy for various
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preparations as journald might end up accessing the file system before it was
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entirely set up, as soon as it was writable.
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With this change we make scheduling when to start writing to /var/log/journal
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explicit. This means persistent mode now requires
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systemd-journal-flush.service in the mix to work, as otherwise journald would
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never write to the directory.
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See: #1397
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(cherry-picked from commit f78273c8dacf678cc8fd7387f678e6344a99405c)
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Resolves: #1364092
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---
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 src/journal/journald-server.c | 21 +++++++++++----------
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 src/journal/journald-server.h |  2 +-
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 src/journal/journald.c        |  2 +-
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 3 files changed, 13 insertions(+), 12 deletions(-)
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diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
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index 96ffda4ec..07426b41e 100644
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--- a/src/journal/journald-server.c
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+++ b/src/journal/journald-server.c
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@@ -918,7 +918,7 @@ finish:
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 }
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 static bool flushed_flag_is_set(void) {
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-        return (access("/run/systemd/journal/flushed", F_OK) >= 0);
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+        return access("/run/systemd/journal/flushed", F_OK) >= 0;
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 }
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 static int system_journal_open(Server *s, bool flush_requested) {
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@@ -926,7 +926,6 @@ static int system_journal_open(Server *s, bool flush_requested) {
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         char *fn;
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         sd_id128_t machine;
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         char ids[33];
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-        bool flushed = false;
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         r = sd_id128_get_machine(&machine);
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         if (r < 0)
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@@ -935,8 +934,8 @@ static int system_journal_open(Server *s, bool flush_requested) {
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         sd_id128_to_string(machine, ids);
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         if (!s->system_journal &&
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-            (s->storage == STORAGE_PERSISTENT || s->storage == STORAGE_AUTO) &&
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-            (flush_requested || (flushed = flushed_flag_is_set()))) {
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+            IN_SET(s->storage, STORAGE_PERSISTENT, STORAGE_AUTO) &&
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+            (flush_requested || flushed_flag_is_set())) {
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                 /* If in auto mode: first try to create the machine
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                  * path, but not the prefix.
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@@ -969,8 +968,8 @@ static int system_journal_open(Server *s, bool flush_requested) {
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                  * Perform an implicit flush to var, leaving the runtime
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                  * journal closed, now that the system journal is back.
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                  */
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-                if (s->runtime_journal && flushed)
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-                        (void) server_flush_to_var(s);
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+                if (!flush_requested)
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+                        (void) server_flush_to_var(s, true);
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         }
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         if (!s->runtime_journal &&
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@@ -1021,7 +1020,7 @@ static int system_journal_open(Server *s, bool flush_requested) {
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         return r;
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 }
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-int server_flush_to_var(Server *s) {
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+int server_flush_to_var(Server *s, bool require_flag_file) {
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         sd_id128_t machine;
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         sd_journal *j = NULL;
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         char ts[FORMAT_TIMESPAN_MAX];
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@@ -1031,13 +1030,15 @@ int server_flush_to_var(Server *s) {
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         assert(s);
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-        if (s->storage != STORAGE_AUTO &&
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-            s->storage != STORAGE_PERSISTENT)
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+        if (!IN_SET(s->storage, STORAGE_AUTO, STORAGE_PERSISTENT))
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                 return 0;
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         if (!s->runtime_journal)
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                 return 0;
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+        if (require_flag_file && !flushed_flag_is_set())
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+                return 0;
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+
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         system_journal_open(s, true);
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         if (!s->system_journal)
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@@ -1243,7 +1244,7 @@ static int dispatch_sigusr1(sd_event_source *es, const struct signalfd_siginfo *
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         log_info("Received request to flush runtime journal from PID %"PRIu32, si->ssi_pid);
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-        (void) server_flush_to_var(s);
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+        (void) server_flush_to_var(s, false);
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         server_sync(s);
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         server_vacuum(s);
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diff --git a/src/journal/journald-server.h b/src/journal/journald-server.h
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index b1263a758..7a456c2d5 100644
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--- a/src/journal/journald-server.h
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+++ b/src/journal/journald-server.h
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@@ -173,6 +173,6 @@ void server_sync(Server *s);
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 void server_vacuum(Server *s);
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 void server_rotate(Server *s);
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 int server_schedule_sync(Server *s, int priority);
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-int server_flush_to_var(Server *s);
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+int server_flush_to_var(Server *s, bool require_flag_file);
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 void server_maybe_append_tags(Server *s);
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 int server_process_datagram(sd_event_source *es, int fd, uint32_t revents, void *userdata);
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diff --git a/src/journal/journald.c b/src/journal/journald.c
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index 80f4634f6..15bbcbe3d 100644
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--- a/src/journal/journald.c
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+++ b/src/journal/journald.c
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@@ -58,7 +58,7 @@ int main(int argc, char *argv[]) {
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                 goto finish;
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         server_vacuum(&server);
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-        server_flush_to_var(&server);
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+        server_flush_to_var(&server, true);
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         server_flush_dev_kmsg(&server);
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         log_debug("systemd-journald running as pid "PID_FMT, getpid());