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

1 files changed, 107 insertions, 0 deletions

diff --git a/src/readahead-common.c b/src/readahead-common.c
new file mode 100644
index 0000000000..8533717d47
--- /dev/null
+++ b/src/readahead-common.c
@@ -0,0 +1,107 @@
+/*-*- 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 <libudev.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "log.h"
+#include "readahead-common.h"
+#include "util.h"
+
+int file_verify(int fd, const char *fn, struct stat *st) {
+        assert(fd >= 0);
+        assert(fn);
+        assert(st);
+
+        if (fstat(fd, st) < 0) {
+                log_warning("fstat(%s) failed: %m", fn);
+                return -errno;
+        }
+
+        if (!S_ISREG(st->st_mode)) {
+                log_debug("Not preloading special file %s", fn);
+                return 0;
+        }
+
+        if (st->st_size <= 0 || st->st_size > READAHEAD_FILE_SIZE_MAX) {
+                log_debug("Not preloading file %s with size out of bounds %zi", fn, st->st_size);
+                return 0;
+        }
+
+        return 1;
+}
+
+int fs_on_ssd(const char *p) {
+        struct stat st;
+        struct udev *udev = NULL;
+        struct udev_device *udev_device = NULL, *look_at = NULL;
+        bool b = false;
+        const char *devtype, *rotational, *model, *id;
+
+        assert(p);
+
+        if (stat(p, &st) < 0)
+                return -errno;
+
+        if (!(udev = udev_new()))
+                return -ENOMEM;
+
+        if (!(udev_device = udev_device_new_from_devnum(udev, 'b', st.st_dev)))
+                goto finish;
+
+        if ((devtype = udev_device_get_property_value(udev_device, "DEVTYPE")) &&
+            streq(devtype, "partition"))
+                look_at = udev_device_get_parent(udev_device);
+        else
+                look_at = udev_device;
+
+        if (!look_at)
+                goto finish;
+
+        /* First, try high-level property */
+        if ((id = udev_device_get_property_value(look_at, "ID_SSD"))) {
+                b = streq(id, "1");
+                goto finish;
+        }
+
+        /* Second, try kernel attribute */
+        if ((rotational = udev_device_get_sysattr_value(look_at, "queue/rotational")))
+                if ((b = streq(rotational, "0")))
+                        goto finish;
+
+        /* Finally, fallback to heuristics */
+        if (!(look_at = udev_device_get_parent(look_at)))
+                goto finish;
+
+        if ((model = udev_device_get_sysattr_value(look_at, "model")))
+                b = !!strstr(model, "SSD");
+
+finish:
+        if (udev_device)
+                udev_device_unref(udev_device);
+
+        if (udev)
+                udev_unref(udev);
+
+        return b;
+}