From 2a0f1b2c7c1e920178741f0942734a1b3ec44801 Mon Sep 17 00:00:00 2001 From: Euler Robot 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 --- ...dle-kernel-without-device-mapper-sup.patch | 79 +++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 virdevmapper-Handle-kernel-without-device-mapper-sup.patch diff --git a/virdevmapper-Handle-kernel-without-device-mapper-sup.patch b/virdevmapper-Handle-kernel-without-device-mapper-sup.patch new file mode 100644 index 0000000..ba25626 --- /dev/null +++ b/virdevmapper-Handle-kernel-without-device-mapper-sup.patch @@ -0,0 +1,79 @@ +From 83298f3086380c9b3b3ec39a2d6bf7b33592683b 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 b43dbefa9a..a81e2edee4 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", +@@ -300,8 +308,16 @@ 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); + } +-- +2.27.0 +