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

1 files changed, 437 insertions, 0 deletions

diff --git a/src/readahead-collect.c b/src/readahead-collect.c
new file mode 100644
index 0000000000..93a04521f3
--- /dev/null
+++ b/src/readahead-collect.c
@@ -0,0 +1,437 @@
+/*-*- 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 <linux/fanotify.h>
+#include <sys/signalfd.h>
+#include <sys/poll.h>
+#include <sys/mman.h>
+#include <linux/fs.h>
+#include <linux/fiemap.h>
+#include <sys/ioctl.h>
+
+#include "missing.h"
+#include "util.h"
+#include "set.h"
+#include "sd-daemon.h"
+#include "ioprio.h"
+#include "readahead-common.h"
+
+/*
+   fixme:
+
+     - BTRFS_IOC_DEFRAG
+*/
+
+#define MINCORE_VEC_SIZE (READAHEAD_FILE_SIZE_MAX/PAGE_SIZE)
+
+static int pack_file(FILE *pack, const char *fn) {
+        struct stat st;
+        void *start = MAP_FAILED;
+        uint8_t vec[MINCORE_VEC_SIZE];
+        uint32_t b, c;
+        size_t l, pages;
+        bool mapped;
+        int r = 0, fd = -1, k;
+
+        assert(pack);
+        assert(fn);
+
+        if ((fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW)) < 0) {
+                log_warning("open(%s) failed: %m", fn);
+                r = -errno;
+                goto finish;
+        }
+
+        if ((k = file_verify(fd, fn, &st)) <= 0) {
+                r = k;
+                goto finish;
+        }
+
+        l = PAGE_ALIGN(st.st_size);
+        if ((start = mmap(NULL, l, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
+                log_warning("mmap(%s) failed: %m", fn);
+                r = -errno;
+                goto finish;
+        }
+
+        if (mincore(start, l, vec) < 0) {
+                log_warning("mincore(%s) failed: %m", fn);
+                r = -errno;
+                goto finish;
+        }
+
+        fputs(fn, pack);
+        fputc('\n', pack);
+
+        pages = l / PAGE_SIZE;
+        mapped = false;
+        for (c = 0; c < pages; c++) {
+                bool new_mapped = (vec[c] & 1);
+
+                if (!mapped && new_mapped)
+                        b = c;
+                else if (mapped && !new_mapped) {
+                        fwrite(&b, sizeof(b), 1, pack);
+                        fwrite(&c, sizeof(c), 1, pack);
+
+                        log_debug("%s: page %u to %u", fn, b, c);
+                }
+
+                mapped = new_mapped;
+        }
+
+        /* We don't write any range data if we should read the entire file */
+        if (mapped && b > 0) {
+                fwrite(&b, sizeof(b), 1, pack);
+                fwrite(&c, sizeof(c), 1, pack);
+
+                log_debug("%s: page %u to %u", fn, b, c);
+        }
+
+        /* End marker */
+        b = 0;
+        fwrite(&b, sizeof(b), 1, pack);
+        fwrite(&b, sizeof(b), 1, pack);
+
+finish:
+        if (start != MAP_FAILED)
+                munmap(start, l);
+
+        if (fd >= 0)
+                close_nointr_nofail(fd);
+
+        return r;
+}
+
+static unsigned long fd_first_block(int fd) {
+        struct {
+                struct fiemap fiemap;
+                struct fiemap_extent extent;
+        } data;
+
+        zero(data);
+        data.fiemap.fm_length = ~0ULL;
+        data.fiemap.fm_extent_count = 1;
+
+        if (ioctl(fd, FS_IOC_FIEMAP, &data) < 0)
+                return 0;
+
+        if (data.fiemap.fm_mapped_extents <= 0)
+                return 0;
+
+        if (data.fiemap.fm_extents[0].fe_flags & FIEMAP_EXTENT_UNKNOWN)
+                return 0;
+
+        return (unsigned long) data.fiemap.fm_extents[0].fe_physical;
+}
+
+struct item {
+        const char *path;
+        unsigned long block;
+};
+
+static int qsort_compare(const void *a, const void *b) {
+        const struct item *i, *j;
+
+        i = a;
+        j = b;
+
+        if (i->block < j->block)
+                return -1;
+        if (i->block > j->block)
+                return 1;
+
+        return strcmp(i->path, j->path);
+}
+
+static int collect(const char *root) {
+        enum {
+                FD_FANOTIFY,
+                FD_SIGNAL,
+                _FD_MAX
+        };
+        struct pollfd pollfd[_FD_MAX];
+        int fanotify_fd = -1, signal_fd = -1, r = 0;
+        pid_t my_pid;
+        Hashmap *files = NULL;
+        Iterator i;
+        char *p, *q;
+        sigset_t mask;
+        FILE *pack = NULL;
+        char *pack_fn_new = NULL, *pack_fn = NULL;
+        bool on_ssd;
+
+        assert(root);
+
+        if (ioprio_set(IOPRIO_WHO_PROCESS, getpid(), IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)) < 0)
+                log_warning("Failed to set IDLE IO priority class: %m");
+
+        assert_se(sigemptyset(&mask) == 0);
+        sigset_add_many(&mask, SIGINT, SIGTERM, -1);
+        assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
+
+        if ((signal_fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
+                log_error("signalfd(): %m");
+                r = -errno;
+                goto finish;
+        }
+
+        if (!(files = hashmap_new(string_hash_func, string_compare_func))) {
+                log_error("Failed to allocate set.");
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        if ((fanotify_fd = fanotify_init(FAN_CLOEXEC, O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_NOATIME)) < 0)  {
+                log_error("Failed to create fanotify object: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        if (fanotify_mark(fanotify_fd, FAN_MARK_ADD|FAN_MARK_MOUNT, FAN_OPEN, AT_FDCWD, root) < 0) {
+                log_error("Failed to mark %s: %m", root);
+                r = -errno;
+                goto finish;
+        }
+
+        my_pid = getpid();
+
+        zero(pollfd);
+        pollfd[FD_FANOTIFY].fd = fanotify_fd;
+        pollfd[FD_FANOTIFY].events = POLLIN;
+        pollfd[FD_SIGNAL].fd = signal_fd;
+        pollfd[FD_SIGNAL].events = POLLIN;
+
+        sd_notify(0,
+                  "READY=1\n"
+                  "STATUS=Collecting readahead data");
+
+        log_debug("Collecting...");
+
+        for (;;) {
+                union {
+                        struct fanotify_event_metadata metadata;
+                        char buffer[4096];
+                } data;
+                ssize_t n;
+                struct fanotify_event_metadata *m;
+
+                if (poll(pollfd, _FD_MAX, -1) < 0) {
+
+                        if (errno == EINTR)
+                                continue;
+
+                        log_error("poll(): %m");
+                        r = -errno;
+                        goto finish;
+                }
+
+                if (pollfd[FD_SIGNAL].revents != 0)
+                        break;
+
+                if ((n = read(fanotify_fd, &data, sizeof(data))) < 0) {
+
+                        if (errno == EINTR || errno == EAGAIN)
+                                continue;
+
+                        log_error("Failed to read event: %m");
+                        r = -errno;
+                        goto finish;
+                }
+
+                m = &data.metadata;
+                while (FAN_EVENT_OK(m, n)) {
+
+                        if (m->pid != my_pid && m->fd >= 0) {
+                                char fn[PATH_MAX];
+                                int k;
+
+                                snprintf(fn, sizeof(fn), "/proc/self/fd/%i", m->fd);
+                                char_array_0(fn);
+
+                                if ((k = readlink_malloc(fn, &p)) >= 0) {
+
+                                        if (hashmap_get(files, p))
+                                                /* Already read */
+                                                free(p);
+                                        else {
+                                                unsigned long ul;
+
+                                                ul = fd_first_block(m->fd);
+
+                                                if ((k = hashmap_put(files, p, ULONG_TO_PTR(ul))) < 0) {
+
+                                                        if (k != -EEXIST)
+                                                                log_warning("set_put() failed: %s", strerror(-k));
+
+                                                        free(p);
+                                                }
+                                        }
+
+                                } else
+                                        log_warning("readlink(%s) failed: %s", fn, strerror(-k));
+                        }
+
+                        if (m->fd)
+                                close_nointr_nofail(m->fd);
+
+                        m = FAN_EVENT_NEXT(m, n);
+                }
+
+        }
+
+        if (fanotify_fd >= 0) {
+                close_nointr_nofail(fanotify_fd);
+                fanotify_fd = -1;
+        }
+
+        log_debug("Writing Pack File...");
+
+        on_ssd = fs_on_ssd(root);
+        log_debug("On SSD: %s", yes_no(on_ssd));
+
+        asprintf(&pack_fn, "%s/.readahead", root);
+        asprintf(&pack_fn_new, "%s/.readahead.new", root);
+
+        if (!pack_fn || !pack_fn_new) {
+                log_error("Out of memory");
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        if (!(pack = fopen(pack_fn_new, "we"))) {
+                log_error("Failed to open pack file: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        fputs(CANONICAL_HOST "\n", pack);
+        putc(on_ssd ? 'S' : 'R', pack);
+
+        if (on_ssd) {
+
+                /* On SSD, just write things out in the order the
+                 * files where accessed */
+
+                HASHMAP_FOREACH_KEY(q, p, files, i)
+                        pack_file(pack, p);
+        } else {
+                struct item *ordered, *j;
+                unsigned k, n;
+
+                /* On rotating media, order things by the block
+                 * numbers */
+
+                log_debug("Ordering...");
+
+                n = hashmap_size(files);
+                if (!(ordered = new(struct item, n))) {
+                        log_error("Out of memory");
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                j = ordered;
+                HASHMAP_FOREACH_KEY(q, p, files, i) {
+                        j->path = p;
+                        j->block = PTR_TO_ULONG(q);
+                        j++;
+                }
+
+                assert(ordered + n == j);
+
+                qsort(ordered, n, sizeof(struct item), qsort_compare);
+
+                for (k = 0; k < n; k++)
+                        pack_file(pack, ordered[k].path);
+
+                free(ordered);
+        }
+
+        log_debug("Finalizing...");
+
+        fflush(pack);
+
+        if (ferror(pack)) {
+                log_error("Failed to write pack file.");
+                r = -EIO;
+                goto finish;
+        }
+
+        if (rename(pack_fn_new, pack_fn) < 0) {
+                log_error("Failed to rename readahead file: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        fclose(pack);
+        pack = NULL;
+
+        log_debug("Done.");
+
+finish:
+        if (fanotify_fd >= 0)
+                close_nointr_nofail(fanotify_fd);
+
+        if (signal_fd >= 0)
+                close_nointr_nofail(signal_fd);
+
+        if (pack) {
+                fclose(pack);
+                unlink(pack_fn_new);
+        }
+
+        free(pack_fn_new);
+        free(pack_fn);
+
+        while ((p = hashmap_steal_first_key(files)))
+                free(q);
+
+        hashmap_free(files);
+
+        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 (collect("/") < 0)
+                return 1;
+
+        return 0;
+}