[systemd-devel] [PATCH 2/6] readahead-common:fs_on_ssd() stat might not get the real device name

[harald at redhat.com]

From: Harald Hoyer <harald at redhat.com>

btrfs returns a major(0) for its device, so try to find the mountpoint and real device.
---
 src/readahead-common.c |   36 ++++++++++++++++++++++++++++++++++--
 1 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/readahead-common.c b/src/readahead-common.c
index 8533717..1ff027d 100644
--- a/src/readahead-common.c
+++ b/src/readahead-common.c
@@ -51,6 +51,25 @@ int file_verify(int fd, const char *fn, struct stat *st) {
         return 1;
 }
 
+static char *get_devname(const char *mountpoint)
+{
+        FILE *fp;
+        int maj, min;
+	char mp[1024], dev[1024];
+
+        fp = fopen("/proc/self/mountinfo", "r");
+        if (fp == NULL)
+                return NULL;
+        while (fscanf(fp, "%*s %*s %i:%i %*s %1024s %*s %*s %*s %1024s %*[^\n]", &maj, &min, mp, dev) == 4) {
+                if (strcmp(mountpoint, mp) == 0) {
+			fclose(fp);
+                        return strdup(dev);
+                }
+        }
+        fclose(fp);
+        return NULL;
+}
+
 int fs_on_ssd(const char *p) {
         struct stat st;
         struct udev *udev = NULL;
@@ -66,8 +85,21 @@ int fs_on_ssd(const char *p) {
         if (!(udev = udev_new()))
                 return -ENOMEM;
 
-        if (!(udev_device = udev_device_new_from_devnum(udev, 'b', st.st_dev)))
-                goto finish;
+	if (major(st.st_dev) == 0) {
+		/* special device, might be on a btrfs */
+		int ret = -1;
+		char *devname = get_devname(p);
+		if (devname == NULL)
+			return -EINVAL;
+		ret = stat(devname, &st);
+		free(devname);
+		if (ret < 0) {
+			return -EINVAL;
+		}
+	}
+
+	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"))
-- 
1.7.3