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pid1: add env var to override default mount rate limit burst

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I am hitting the rate limit on a busy system with low resources, and
it stalls the boot process which is Very Bad (TM).

(cherry picked from commit 24a4542cfa)

Included in the backport because it's a workaround for an issue introduced
in v249.
This commit is contained in:
Luca Boccassi 2022-12-05 21:05:54 +00:00 committed by Zbigniew Jędrzejewski-Szmek
parent 7c0aacc733
commit c55426445a
2 changed files with 17 additions and 1 deletions
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7
docs/ENVIRONMENT.md
View File

@ -268,6 +268,13 @@ All tools:
it is either set to `system` or `user` depending on whether the NSS/PAM
module is called by systemd in `--system` or `--user` mode.
* `$SYSTEMD_DEFAULT_MOUNT_RATE_LIMIT_BURST` — can be set to override the mount
units burst rate limit for parsing `/proc/self/mountinfo`. On a system with
few resources but many mounts the rate limit may be hit, which will cause the
processing of mount units to stall. The burst limit may be adjusted when the
default is not appropriate for a given system. Defaults to `5`, accepts
positive integers.
`systemd-remount-fs`:
* `$SYSTEMD_REMOUNT_ROOT_RW=1` — if set and no entry for the root directory

11
src/core/mount.c
View File

@ -1908,6 +1908,7 @@ static void mount_enumerate(Manager *m) {
mnt_init_debug(0);
if (!m->mount_monitor) {
unsigned mount_rate_limit_burst = 5;
int fd;
m->mount_monitor = mnt_new_monitor();
@ -1947,7 +1948,15 @@ static void mount_enumerate(Manager *m) {
goto fail;
}
r = sd_event_source_set_ratelimit(m->mount_event_source, 1 * USEC_PER_SEC, 5);
/* Let users override the default (5 in 1s), as it stalls the boot sequence on busy systems. */
const char *e = secure_getenv("SYSTEMD_DEFAULT_MOUNT_RATE_LIMIT_BURST");
if (e) {
r = safe_atou(e, &mount_rate_limit_burst);
if (r < 0)
log_debug("Invalid value in $SYSTEMD_DEFAULT_MOUNT_RATE_LIMIT_BURST, ignoring: %s", e);
}
r = sd_event_source_set_ratelimit(m->mount_event_source, 1 * USEC_PER_SEC, mount_rate_limit_burst);
if (r < 0) {
log_error_errno(r, "Failed to enable rate limit for mount events: %m");
goto fail;