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From 4fab90faea400463fd77e4dc0be1438da59718fd Mon Sep 17 00:00:00 2001
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From: Christian Brauner <christian.brauner@ubuntu.com>
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Date: Wed, 26 Apr 2017 06:18:10 +0200
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Subject: [PATCH] main: improve RLIMIT_NOFILE handling (#5795)
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This has systemd look at /proc/sys/fs/nr_open to find the current maximum of
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open files compiled into the kernel and tries to set the RLIMIT_NOFILE max to
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it. This has the advantage the value chosen as limit is less arbitrary and also
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improves the behavior of systemd in containers that have an rlimit set: When
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systemd currently starts in a container that has RLIMIT_NOFILE set to e.g.
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100000 systemd will lower it to 65536. With this patch systemd will try to set
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the nofile limit to the allowed kernel maximum. If this fails, it will compute
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the minimum of the current set value (the limit that is set on the container)
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and the maximum value as soft limit and the currently set maximum value as the
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maximum value. This way it retains the limit set on the container.
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(cherry picked from commit 6385cb31ef443be3e0d6da5ea62a267a49174688)
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Resolves: #1585913
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---
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src/core/main.c | 12 +++++++++++-
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1 file changed, 11 insertions(+), 1 deletion(-)
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diff --git a/src/core/main.c b/src/core/main.c
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index 5554ef468d..2d70ed07ed 100644
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--- a/src/core/main.c
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+++ b/src/core/main.c
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@@ -1017,6 +1017,8 @@ fail:
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static int bump_rlimit_nofile(struct rlimit *saved_rlimit) {
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struct rlimit nl;
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int r;
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+ int min_max;
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+ _cleanup_free_ char *nr_open = NULL;
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assert(saved_rlimit);
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@@ -1037,8 +1039,16 @@ static int bump_rlimit_nofile(struct rlimit *saved_rlimit) {
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arg_default_rlimit[RLIMIT_NOFILE] = rl;
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}
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+ /* Get current RLIMIT_NOFILE maximum compiled into the kernel. */
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+ r = read_one_line_file("/proc/sys/fs/nr_open", &nr_open);
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+ if (r == 0)
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+ r = safe_atoi(nr_open, &min_max);
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+ /* If we fail, fallback to the hard-coded kernel limit of 1024 * 1024. */
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+ if (r < 0)
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+ min_max = 1024 * 1024;
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+
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/* Bump up the resource limit for ourselves substantially */
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- nl.rlim_cur = nl.rlim_max = 64*1024;
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+ nl.rlim_cur = nl.rlim_max = min_max;
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r = setrlimit_closest(RLIMIT_NOFILE, &nl);
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if (r < 0)
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return log_error_errno(r, "Setting RLIMIT_NOFILE failed: %m");
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