From dac7e7ddd11cd1e4cc20c8bd61dcaa7e01e95744 Mon Sep 17 00:00:00 2001 From: Euler Robot Date: Tue, 18 Aug 2020 11:08:15 +0200 Subject: [PATCH] virdevmapper: Don't cache device-mapper major The device mapper major is needed in virIsDevMapperDevice() which determines whether given device is managed by device-mapper. This number is obtained by parsing /proc/devices and then stored in a global variable so that the file doesn't have to be parsed again. However, as it turns out this logic is flawed - the major number is not static and can change as it can be specified as a parameter when loading the dm-mod module. Unfortunately, I was not able to come up with a good solution and thus the /proc/devices file is being parsed every time we need the device mapper major. Signed-off-by: Michal Privoznik Reviewed-by: Peter Krempa Reviewed-by: Christian Ehrhardt Tested-by: Christian Ehrhardt --- ...pper-Don-t-cache-device-mapper-major.patch | 91 +++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 virdevmapper-Don-t-cache-device-mapper-major.patch diff --git a/virdevmapper-Don-t-cache-device-mapper-major.patch b/virdevmapper-Don-t-cache-device-mapper-major.patch new file mode 100644 index 0000000..b080043 --- /dev/null +++ b/virdevmapper-Don-t-cache-device-mapper-major.patch @@ -0,0 +1,91 @@ +From fb5ac9b0db25984b0d54149dc15b87f513523430 Mon Sep 17 00:00:00 2001 +From: Michal Privoznik +Date: Tue, 18 Aug 2020 11:08:15 +0200 +Subject: [PATCH] virdevmapper: Don't cache device-mapper major + +The device mapper major is needed in virIsDevMapperDevice() which +determines whether given device is managed by device-mapper. This +number is obtained by parsing /proc/devices and then stored in a +global variable so that the file doesn't have to be parsed again. +However, as it turns out this logic is flawed - the major number +is not static and can change as it can be specified as a +parameter when loading the dm-mod module. + +Unfortunately, I was not able to come up with a good solution and +thus the /proc/devices file is being parsed every time we need +the device mapper major. + +Signed-off-by: Michal Privoznik +Reviewed-by: Peter Krempa +Reviewed-by: Christian Ehrhardt +Tested-by: Christian Ehrhardt +--- + src/util/virdevmapper.c | 17 +++++------------ + 1 file changed, 5 insertions(+), 12 deletions(-) + +diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c +index a471504176..b43dbefa9a 100644 +--- a/src/util/virdevmapper.c ++++ b/src/util/virdevmapper.c +@@ -46,11 +46,9 @@ + + G_STATIC_ASSERT(BUF_SIZE > sizeof(struct dm_ioctl)); + +-static unsigned int virDMMajor; +- + + static int +-virDevMapperOnceInit(void) ++virDevMapperGetMajor(unsigned int *major) + { + g_autofree char *buf = NULL; + VIR_AUTOSTRINGLIST lines = NULL; +@@ -69,7 +67,7 @@ virDevMapperOnceInit(void) + + if (sscanf(lines[i], "%u %ms\n", &maj, &dev) == 2 && + STREQ(dev, DM_NAME)) { +- virDMMajor = maj; ++ *major = maj; + break; + } + } +@@ -85,9 +83,6 @@ virDevMapperOnceInit(void) + } + + +-VIR_ONCE_GLOBAL_INIT(virDevMapper); +- +- + static void * + virDMIoctl(int controlFD, int cmd, struct dm_ioctl *dm, char **buf) + { +@@ -305,9 +300,6 @@ virDevMapperGetTargets(const char *path, + * consist of devices or yet another targets. If that's the + * case, we have to stop recursion somewhere. */ + +- if (virDevMapperInitialize() < 0) +- return -1; +- + if ((controlFD = virDMOpen()) < 0) + return -1; + +@@ -319,13 +311,14 @@ bool + virIsDevMapperDevice(const char *dev_name) + { + struct stat buf; ++ unsigned int major; + +- if (virDevMapperInitialize() < 0) ++ if (virDevMapperGetMajor(&major) < 0) + return false; + + if (!stat(dev_name, &buf) && + S_ISBLK(buf.st_mode) && +- major(buf.st_rdev) == virDMMajor) ++ major(buf.st_rdev) == major) + return true; + + return false; +-- +2.27.0 +