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From 29a17260cc1875640e62f63bfe7fa9661dc9fe70 Mon Sep 17 00:00:00 2001
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Message-Id: <29a17260cc1875640e62f63bfe7fa9661dc9fe70@dist-git>
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From: Michal Privoznik <mprivozn@redhat.com>
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Date: Wed, 20 Nov 2019 14:34:11 +0100
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Subject: [PATCH] qemu: Forcibly mknod() even if it exists
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Another weird bug appeared concerning qemu namespaces. Basically
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the problem is as follows:
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1) Issue an API that causes libvirt to create a node in domain's
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namespace, say /dev/nvme0n1 with 8:0 as major:minor (the API can
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be attach-disk for instance). Or simply create the node from a
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console by hand.
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2) Detach the disk from qemu.
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3) Do something that makes /dev/nvme0n1 change it's minor number.
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4) Try to attach the disk again.
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The problem is, in a few cases - like disk-detach - we don't
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remove the corresponding /dev node from the mount namespace
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(because it may be used by some other disk's backing chain). But
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this creates a problem, because if the node changes its MAJ:MIN
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numbers we don't propagate the change into the domain's
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namespace. We do plain mknod() and ignore EEXIST which obviously
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is not enough because it doesn't guarantee that the node has
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updated MAJ:MIN pair.
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Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1752978
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
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(cherry picked from commit cdd8a6690ee3fa4b4b8ca1d4531924bd33be136a)
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Message-Id: <058a9025fdcb817d3334e6c5a7c6a4fe1e95e761.1574256841.git.mprivozn@redhat.com>
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Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
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---
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src/qemu/qemu_domain.c | 25 +++++++++----------------
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1 file changed, 9 insertions(+), 16 deletions(-)
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diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
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index e7d7a3baeb..3c67769771 100644
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--- a/src/qemu/qemu_domain.c
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+++ b/src/qemu/qemu_domain.c
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@@ -11191,16 +11191,14 @@ qemuDomainCreateDeviceRecursive(const char *device,
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allow_noent, ttl - 1) < 0)
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goto cleanup;
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} else if (isDev) {
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- if (create &&
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- mknod(devicePath, sb.st_mode, sb.st_rdev) < 0) {
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- if (errno == EEXIST) {
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- ret = 0;
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- } else {
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+ if (create) {
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+ unlink(devicePath);
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+ if (mknod(devicePath, sb.st_mode, sb.st_rdev) < 0) {
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virReportSystemError(errno,
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_("Failed to make device %s"),
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devicePath);
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+ goto cleanup;
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}
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- goto cleanup;
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}
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} else if (isReg) {
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if (create &&
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@@ -11969,17 +11967,12 @@ qemuDomainAttachDeviceMknodHelper(pid_t pid ATTRIBUTE_UNUSED,
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} else if (isDev) {
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VIR_DEBUG("Creating dev %s (%d,%d)",
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data->file, major(data->sb.st_rdev), minor(data->sb.st_rdev));
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+ unlink(data->file);
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if (mknod(data->file, data->sb.st_mode, data->sb.st_rdev) < 0) {
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- /* Because we are not removing devices on hotunplug, or
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- * we might be creating part of backing chain that
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- * already exist due to a different disk plugged to
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- * domain, accept EEXIST. */
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- if (errno != EEXIST) {
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- virReportSystemError(errno,
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- _("Unable to create device %s"),
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- data->file);
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- goto cleanup;
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- }
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+ virReportSystemError(errno,
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+ _("Unable to create device %s"),
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+ data->file);
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+ goto cleanup;
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} else {
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delDevice = true;
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}
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--
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2.24.0
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