coredump: add simple coredump vacuuming

When disk space taken up by coredumps grows beyond a configured limit
start removing the oldest coredump of the user with the most coredumps,
until we get below the limit again.

1 files changed, 272 insertions, 0 deletions

diff --git a/src/journal/coredump-vacuum.c b/src/journal/coredump-vacuum.c
new file mode 100644
index 000000000..ad2e2fa7f
--- /dev/null
+++ b/src/journal/coredump-vacuum.c
@@ -0,0 +1,272 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/statvfs.h>
+
+#include "util.h"
+#include "time-util.h"
+#include "hashmap.h"
+#include "macro.h"
+
+#include "coredump-vacuum.h"
+
+#define DEFAULT_MAX_USE_LOWER (off_t) (1ULL*1024ULL*1024ULL)           /* 1 MiB */
+#define DEFAULT_MAX_USE_UPPER (off_t) (4ULL*1024ULL*1024ULL*1024ULL)   /* 4 GiB */
+#define DEFAULT_KEEP_FREE_UPPER (off_t) (4ULL*1024ULL*1024ULL*1024ULL) /* 4 GiB */
+#define DEFAULT_KEEP_FREE (off_t) (1024ULL*1024ULL)                    /* 1 MB */
+
+struct vacuum_candidate {
+        unsigned n_files;
+        char *oldest_file;
+        usec_t oldest_mtime;
+};
+
+static void vacuum_candidate_free(struct vacuum_candidate *c) {
+        if (!c)
+                return;
+
+        free(c->oldest_file);
+        free(c);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(struct vacuum_candidate*, vacuum_candidate_free);
+
+static void vacuum_candidate_hasmap_free(Hashmap *h) {
+        struct vacuum_candidate *c;
+
+        while ((c = hashmap_steal_first(h)))
+                vacuum_candidate_free(c);
+
+        hashmap_free(h);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(Hashmap*, vacuum_candidate_hasmap_free);
+
+static int uid_from_file_name(const char *filename, uid_t *uid) {
+        const char *p, *e, *u;
+
+        p = startswith(filename, "core.");
+        if (!p)
+                return -EINVAL;
+
+        /* Skip the comm field */
+        p = strchr(p, '.');
+        if (!p)
+                return -EINVAL;
+        p++;
+
+        /* Find end up UID */
+        e = strchr(p, '.');
+        if (!e)
+                return -EINVAL;
+
+        u = strndupa(p, e-p);
+        return parse_uid(u, uid);
+}
+
+static bool vacuum_necessary(int fd, off_t sum, off_t keep_free, off_t max_use) {
+        off_t fs_size = 0, fs_free = (off_t) -1;
+        struct statvfs sv;
+
+        assert(fd >= 0);
+
+        if (fstatvfs(fd, &sv) >= 0) {
+                fs_size = sv.f_frsize * sv.f_blocks;
+                fs_free = sv.f_frsize * sv.f_bfree;
+        }
+
+        if (max_use == (off_t) -1) {
+
+                if (fs_size > 0) {
+                        max_use = PAGE_ALIGN(fs_size / 10); /* 10% */
+
+                        if (max_use > DEFAULT_MAX_USE_UPPER)
+                                max_use = DEFAULT_MAX_USE_UPPER;
+
+                        if (max_use < DEFAULT_MAX_USE_LOWER)
+                                max_use = DEFAULT_MAX_USE_LOWER;
+                }
+
+                max_use = DEFAULT_MAX_USE_LOWER;
+        } else
+                max_use = PAGE_ALIGN(max_use);
+
+        if (max_use > 0 && sum > max_use)
+                return true;
+
+        if (keep_free == (off_t) -1) {
+
+                if (fs_size > 0) {
+                        keep_free = PAGE_ALIGN((fs_size * 3) / 20); /* 15% */
+
+                        if (keep_free > DEFAULT_KEEP_FREE_UPPER)
+                                keep_free = DEFAULT_KEEP_FREE_UPPER;
+                } else
+                        keep_free = DEFAULT_KEEP_FREE;
+        } else
+                keep_free = PAGE_ALIGN(keep_free);
+
+        if (keep_free > 0 && fs_free < keep_free)
+                return true;
+
+        return false;
+}
+
+int coredump_vacuum(int exclude_fd, off_t keep_free, off_t max_use) {
+        _cleanup_closedir_ DIR *d = NULL;
+        struct stat exclude_st;
+        int r;
+
+        if (keep_free <= 0 && max_use <= 0)
+                return 0;
+
+        if (exclude_fd >= 0) {
+                if (fstat(exclude_fd, &exclude_st) < 0) {
+                        log_error("Failed to fstat(): %m");
+                        return -errno;
+                }
+        }
+
+        /* This algorithm will keep deleting the oldest file of the
+         * user with the most coredumps until we are back in the size
+         * limits. Note that vacuuming for journal files is different,
+         * because we rely on rate-limiting of the messages there,
+         * to avoid being flooded. */
+
+        d = opendir("/var/lib/systemd/coredump");
+        if (!d) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_error("Can't open coredump directory: %m");
+                return -errno;
+        }
+
+        for (;;) {
+                _cleanup_(vacuum_candidate_hasmap_freep) Hashmap *h = NULL;
+                struct vacuum_candidate *worst = NULL;
+                struct dirent *de;
+                off_t sum = 0;
+
+                rewinddir(d);
+
+                FOREACH_DIRENT(de, d, goto fail) {
+                        struct vacuum_candidate *c;
+                        struct stat st;
+                        uid_t uid;
+                        usec_t t;
+
+                        r = uid_from_file_name(de->d_name, &uid);
+                        if (r < 0)
+                                continue;
+
+                        if (fstatat(dirfd(d), de->d_name, &st, AT_NO_AUTOMOUNT|AT_SYMLINK_NOFOLLOW) < 0) {
+                                if (errno == ENOENT)
+                                        continue;
+
+                                log_warning("Failed to stat /var/lib/systemd/coredump/%s", de->d_name);
+                                continue;
+                        }
+
+                        if (!S_ISREG(st.st_mode))
+                                continue;
+
+                        if (exclude_fd >= 0 &&
+                            exclude_st.st_dev == st.st_dev &&
+                            exclude_st.st_ino == st.st_ino)
+                                continue;
+
+                        r = hashmap_ensure_allocated(&h, NULL, NULL);
+                        if (r < 0)
+                                return log_oom();
+
+                        t = timespec_load(&st.st_mtim);
+
+                        c = hashmap_get(h, UINT32_TO_PTR(uid));
+                        if (c) {
+
+                                if (t < c->oldest_mtime) {
+                                        char *n;
+
+                                        n = strdup(de->d_name);
+                                        if (!n)
+                                                return log_oom();
+
+                                        free(c->oldest_file);
+                                        c->oldest_file = n;
+                                        c->oldest_mtime = t;
+                                }
+
+                        } else {
+                                _cleanup_(vacuum_candidate_freep) struct vacuum_candidate *n = NULL;
+
+                                n = new0(struct vacuum_candidate, 1);
+                                if (!n)
+                                        return log_oom();
+
+                                n->oldest_file = strdup(de->d_name);
+                                if (!n->oldest_file)
+                                        return log_oom();
+
+                                n->oldest_mtime = t;
+
+                                r = hashmap_put(h, UINT32_TO_PTR(uid), n);
+                                if (r < 0)
+                                        return log_oom();
+
+                                c = n;
+                                n = NULL;
+                        }
+
+                        c->n_files++;
+
+                        if (!worst ||
+                            worst->n_files < c->n_files ||
+                            (worst->n_files == c->n_files && c->oldest_mtime < worst->oldest_mtime))
+                                worst = c;
+
+                        sum += st.st_blocks * 512;
+                }
+
+                if (!worst)
+                        break;
+
+                r = vacuum_necessary(dirfd(d), sum, keep_free, max_use);
+                if (r <= 0)
+                        return r;
+
+                if (unlinkat(dirfd(d), worst->oldest_file, 0) < 0) {
+
+                        if (errno == ENOENT)
+                                continue;
+
+                        log_error("Failed to remove file %s: %m", worst->oldest_file);
+                        return -errno;
+                } else
+                        log_info("Removed old coredump %s.", worst->oldest_file);
+        }
+
+        return 0;
+
+fail:
+        log_error("Failed to read directory: %m");
+        return -errno;
+}