10:07 a.m.
When creating /dev nodes in a QEMU domain's namespace the first
thing we simply do is unlink() the path and create it again. This
aims to solve the case when a file changed type/major/minor in
the host and thus we need to reflect this in the guest's
namespace. Fair enough, except we can be a bit more clever about
it: firstly check whether the path doesn't already exist or isn't
already of the correct type/major/minor and do the
unlink+creation only if needed.
Currently, this is implemented only for symlinks and
block/character devices. For regular files/directories (which are
less common) this might be implemented one day, but not today.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
Use --ignore-space-change for the best experience.
src/qemu/qemu_namespace.c | 71 ++++++++++++++++++++++++---------------
1 file changed, 44 insertions(+), 27 deletions(-)
diff --git a/src/qemu/qemu_namespace.c b/src/qemu/qemu_namespace.c
index 1132fd04e5..0714a2d0de 100644
--- a/src/qemu/qemu_namespace.c
+++ b/src/qemu/qemu_namespace.c
@@ -948,38 +948,55 @@ qemuNamespaceMknodOne(qemuNamespaceMknodItem *data)
}
if (isLink) {
- VIR_DEBUG("Creating symlink %s -> %s", data->file,
data->target);
+ g_autoptr(GError) gerr = NULL;
+ g_autofree char *target = NULL;
- /* First, unlink the symlink target. Symlinks change and
- * therefore we have no guarantees that pre-existing
- * symlink is still valid. */
- if (unlink(data->file) < 0 &&
- errno != ENOENT) {
- virReportSystemError(errno,
- _("Unable to remove symlink %s"),
- data->file);
- goto cleanup;
- }
-
- if (symlink(data->target, data->file) < 0) {
- virReportSystemError(errno,
- _("Unable to create symlink %s (pointing to
%s)"),
- data->file, data->target);
- goto cleanup;
+ if ((target = g_file_read_link(data->file, &gerr)) &&
+ STREQ(target, data->target)) {
+ VIR_DEBUG("Skipping symlink %s -> %s which exists and points to
correct target",
+ data->file, data->target);
} else {
- delDevice = true;
+ VIR_DEBUG("Creating symlink %s -> %s", data->file,
data->target);
+
+ /* First, unlink the symlink target. Symlinks change and
+ * therefore we have no guarantees that pre-existing
+ * symlink is still valid. */
+ if (unlink(data->file) < 0 &&
+ errno != ENOENT) {
+ virReportSystemError(errno,
+ _("Unable to remove symlink %s"),
+ data->file);
+ goto cleanup;
+ }
+
+ if (symlink(data->target, data->file) < 0) {
+ virReportSystemError(errno,
+ _("Unable to create symlink %s (pointing to
%s)"),
+ data->file, data->target);
+ goto cleanup;
+ } else {
+ delDevice = true;
+ }
}
} else if (isDev) {
- VIR_DEBUG("Creating dev %s (%d,%d)",
- data->file, major(data->sb.st_rdev),
minor(data->sb.st_rdev));
- unlink(data->file);
- if (mknod(data->file, data->sb.st_mode, data->sb.st_rdev) < 0) {
- virReportSystemError(errno,
- _("Unable to create device %s"),
- data->file);
- goto cleanup;
+ GStatBuf sb;
+
+ if (g_lstat(data->file, &sb) >= 0 &&
+ sb.st_rdev == data->sb.st_rdev) {
+ VIR_DEBUG("Skipping dev %s (%d,%d) which exists and has correct
MAJ:MIN",
+ data->file, major(data->sb.st_rdev),
minor(data->sb.st_rdev));
} else {
- delDevice = true;
+ VIR_DEBUG("Creating dev %s (%d,%d)",
+ data->file, major(data->sb.st_rdev),
minor(data->sb.st_rdev));
+ unlink(data->file);
+ if (mknod(data->file, data->sb.st_mode, data->sb.st_rdev) < 0) {
+ virReportSystemError(errno,
+ _("Unable to create device %s"),
+ data->file);
+ goto cleanup;
+ } else {
+ delDevice = true;
+ }
}
} else if (isReg || isDir) {
/* We are not cleaning up disks on virDomainDetachDevice
--
2.34.1