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From 3947abeeb92069705229bff681b28d8ac78aedaa Mon Sep 17 00:00:00 2001
From: Colin Watson <cjwatson@ubuntu.com>
Date: Fri, 28 Mar 2014 17:10:16 +0000
Subject: udev handling
Run udevadm settle around partition table rereads, to avoid races.
This should be replaced by a proper completion-notification mechanism
between the kernel and udev.
Forwarded: no
Last-Update: 2019-10-11
Patch-Name: udevadm-settle.patch
---
libparted/arch/linux.c | 56 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 54 insertions(+), 2 deletions(-)
diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index ccbba865..f6f72360 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -26,6 +26,7 @@
#include <parted/fdasd.h>
#endif
+#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
@@ -3250,10 +3251,52 @@ _have_blkpg ()
return have_blkpg = kver >= KERNEL_VERSION (2,4,0) ? 1 : 0;
}
+static int
+_chrooted ()
+{
+ static int cached = -1;
+ struct stat root, init_root;
+
+ if (cached != -1)
+ return cached;
+
+ if (stat ("/", &root) || stat ("/proc/1/root", &init_root))
+ /* We can't tell, but are unlikely to be able to tell in the
+ * future either.
+ */
+ cached = 0;
+ else if (root.st_dev == init_root.st_dev &&
+ root.st_ino == init_root.st_ino)
+ /* / has the same dev/ino as /sbin/init's root, so we're not
+ * in a chroot.
+ */
+ cached = 0;
+ else
+ /* We must be in a chroot. */
+ cached = 1;
+
+ return cached;
+}
+
/* Return nonzero upon success, 0 if something fails. */
static int
linux_disk_commit (PedDisk* disk)
{
+ int ret = 1;
+
+ /* Modern versions of udev may notice the write activity on
+ * partition devices caused by _flush_cache, and may decide to
+ * synthesise some change events as a result. These may in turn run
+ * programs that open partition devices, which will race with us
+ * trying to remove those devices. To avoid this, we need to wait
+ * until udevd has finished processing its event queue.
+ * TODO: for upstream submission, this should check whether udevadm
+ * exists on $PATH.
+ */
+ if (!_chrooted () && system ("udevadm settle") != 0) {
+ /* ignore failures */
+ }
+
if (disk->dev->type != PED_DEVICE_FILE) {
/* We now require BLKPG support. If this assertion fails,
@@ -3263,10 +3306,19 @@ linux_disk_commit (PedDisk* disk)
assert (_have_blkpg ());
if (!_disk_sync_part_table (disk))
- return 0;
+ ret = 0;
}
- return 1;
+ /* Now we wait for udevd to finish creating device nodes based on
+ * the above activity, so that callers can reliably use them.
+ * TODO: for upstream submission, this should check whether udevadm
+ * exists on $PATH.
+ */
+ if (!_chrooted () && system ("udevadm settle") != 0) {
+ /* ignore failures */
+ }
+
+ return ret;
}
#if USE_BLKID
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