From feb8564a3cc63bc8f68284063d53ec0d2d81a1cc Mon Sep 17 00:00:00 2001 From: Michal Privoznik Date: Tue, 18 Aug 2020 11:04:24 +0200 Subject: [PATCH] virdevmapper: Handle kernel without device-mapper support In one of my latest patch (v6.6.0~30) I was trying to remove libdevmapper use in favor of our own implementation. However, the code did not take into account that device mapper can be not compiled into the kernel (e.g. be a separate module that's not loaded) in which case /proc/devices won't have the device-mapper major number and thus virDevMapperGetTargets() and/or virIsDevMapperDevice() fails. However, such failure is safe to ignore, because if device mapper is missing then there can't be any multipath devices and thus we don't need to allow the deps in CGroups, nor create them in the domain private namespace, etc. Fixes: 22494556542c676d1b9e7f1c1f2ea13ac17e1e3e Reported-by: Andrea Bolognani Reported-by: Christian Ehrhardt Signed-off-by: Michal Privoznik Reviewed-by: Peter Krempa Reviewed-by: Christian Ehrhardt Tested-by: Christian Ehrhardt --- src/util/virdevmapper.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c index b24d9377f8..3cc399f382 100644 --- a/src/util/virdevmapper.c +++ b/src/util/virdevmapper.c @@ -54,6 +54,9 @@ virDevMapperGetMajor(unsigned int *major) VIR_AUTOSTRINGLIST lines = NULL; size_t i; + if (!virFileExists(CONTROL_PATH)) + return -2; + if (virFileReadAll(PROC_DEVICES, BUF_SIZE, &buf) < 0) return -1; @@ -126,8 +129,13 @@ virDMOpen(void) memset(&dm, 0, sizeof(dm)); - if ((controlFD = open(CONTROL_PATH, O_RDWR)) < 0) + if ((controlFD = open(CONTROL_PATH, O_RDWR)) < 0) { + if (errno == ENOENT) + return -2; + + virReportSystemError(errno, _("Unable to open %s"), CONTROL_PATH); return -1; + } if (!virDMIoctl(controlFD, DM_VERSION, &dm, &tmp)) { virReportSystemError(errno, "%s", @@ -299,8 +307,16 @@ virDevMapperGetTargets(const char *path, * consist of devices or yet another targets. If that's the * case, we have to stop recursion somewhere. */ - if ((controlFD = virDMOpen()) < 0) + if ((controlFD = virDMOpen()) < 0) { + if (controlFD == -2) { + /* The CONTROL_PATH doesn't exist. Probably the + * module isn't loaded, yet. Don't error out, just + * exit. */ + return 0; + } + return -1; + } return virDevMapperGetTargetsImpl(controlFD, path, devPaths, ttl); }