readahead: implement minimal readahead logic based on fanotify(), mincore() and readahead()

1 files changed, 214 insertions, 0 deletions

diff --git a/src/readahead-replay.c b/src/readahead-replay.c
new file mode 100644
index 0000000000..b886857ffb
--- /dev/null
+++ b/src/readahead-replay.c
@@ -0,0 +1,214 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <inttypes.h>
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "missing.h"
+#include "util.h"
+#include "set.h"
+#include "sd-daemon.h"
+#include "ioprio.h"
+#include "readahead-common.h"
+
+static int unpack_file(FILE *pack) {
+        char fn[PATH_MAX];
+        int r = 0, fd = -1;
+        bool any = false;
+        struct stat st;
+
+        assert(pack);
+
+        if (!fgets(fn, sizeof(fn), pack))
+                return 0;
+
+        char_array_0(fn);
+        truncate_nl(fn);
+
+        if ((fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW)) < 0)
+                log_warning("open(%s) failed: %m", fn);
+        else if (file_verify(fd, fn, &st) <= 0) {
+                close_nointr_nofail(fd);
+                fd = -1;
+        }
+
+        for (;;) {
+                uint32_t b, c;
+
+                if (fread(&b, sizeof(b), 1, pack) != 1 ||
+                    fread(&c, sizeof(c), 1, pack) != 1) {
+                        log_error("Premature end of pack file.");
+                        r = -EIO;
+                        goto finish;
+                }
+
+                if (b == 0 && c == 0)
+                        break;
+
+                if (c <= b) {
+                        log_error("Invalid pack file.");
+                        r = -EIO;
+                        goto finish;
+                }
+
+                log_debug("%s: page %u to %u", fn, b, c);
+
+                any = true;
+
+                if (fd >= 0)
+                        if (readahead(fd, b * PAGE_SIZE, (c - b) * PAGE_SIZE) < 0) {
+                                log_warning("readahead() failed: %m");
+                                goto finish;
+                        }
+        }
+
+        if (!any && fd >= 0) {
+                /* if no range is encoded in the pack file this is
+                 * intended to mean that the whole file shall be
+                 * read */
+
+                if (readahead(fd, 0, st.st_size) < 0) {
+                        log_warning("readahead() failed: %m");
+                        goto finish;
+                }
+        }
+
+finish:
+        if (fd >= 0)
+                close_nointr_nofail(fd);
+
+        return r;
+}
+
+static int replay(const char *root) {
+        FILE *pack;
+        char line[LINE_MAX];
+        int r = 0;
+        char *pack_fn = NULL, c;
+        bool on_ssd;
+        int prio;
+
+        assert(root);
+
+        if (asprintf(&pack_fn, "%s/.readahead", root) < 0) {
+                log_error("Out of memory");
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        if ((!(pack = fopen(pack_fn, "re")))) {
+                if (errno == -ENOENT)
+                        log_debug("No pack file found.");
+                else {
+                        log_error("Failed to open pack file: %m");
+                        r = -errno;
+                }
+
+                goto finish;
+        }
+
+        if (!(fgets(line, sizeof(line), pack))) {
+                log_error("Premature end of pack file.");
+                r = -EIO;
+                goto finish;
+        }
+
+        char_array_0(line);
+
+        if (!streq(line, CANONICAL_HOST "\n")) {
+                log_debug("Pack file host type mismatch.");
+                goto finish;
+        }
+
+        if ((c = getc(pack)) == EOF) {
+                log_debug("Premature end of pack file.");
+                r = -EIO;
+                goto finish;
+        }
+
+        /* We do not retest SSD here, so that we can start replaying
+         * before udev is up.*/
+        on_ssd = c == 'S';
+        log_debug("On SSD: %s", yes_no(on_ssd));
+
+        if (on_ssd)
+                prio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0);
+        else
+                prio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 7);
+
+        if (ioprio_set(IOPRIO_WHO_PROCESS, getpid(), prio) < 0)
+                log_warning("Failed to set IDLE IO priority class: %m");
+
+        sd_notify(0,
+                  "READY=1\n"
+                  "STATUS=Replaying readahead data");
+
+        log_debug("Replaying...");
+
+        while (!feof(pack) && !ferror(pack)) {
+                int k;
+
+                if ((k = unpack_file(pack)) < 0) {
+                        r = k;
+                        goto finish;
+                }
+        }
+
+        if (ferror(pack)) {
+                log_error("Failed to read pack file.");
+                r = -EIO;
+                goto finish;
+        }
+
+        log_debug("Done.");
+
+finish:
+        if (pack)
+                fclose(pack);
+
+        free(pack_fn);
+
+        return r;
+}
+
+int main(int argc, char*argv[]) {
+        /* log_set_target(LOG_TARGET_SYSLOG_OR_KMSG); */
+        log_parse_environment();
+        log_open();
+
+        log_set_max_level(LOG_DEBUG);
+
+        if (replay("/") < 0)
+                return 1;
+
+        return 0;
+}