From fb8c44edabd188957fe3e3deb97a605f71c394b8 Mon Sep 17 00:00:00 2001

Message-Id: <fb8c44edabd188957fe3e3deb97a605f71c394b8@dist-git>

From: Michal Privoznik <mprivozn@redhat.com>

Date: Mon, 8 Mar 2021 12:57:32 +0100

Subject: [PATCH] virdevmapper: Don't cache device-mapper major

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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 <mprivozn@redhat.com>

Reviewed-by: Peter Krempa <pkrempa@redhat.com>

Reviewed-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

(cherry picked from commit 82bb167f0d15b733b23931205be3488b83cb9ec6)

Conflicts:

- src/util/virdevmapper.c: The VIR_ONCE_GLOBAL_INIT() call was

  missing a semicolon at EOL which was added there in

  af36f8a641809556ac18dcc076f996033cb2385c which isn't

  backported.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1933557

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Message-Id: <206f7453debcfd7a013317989893be8a0688045c.1615203117.git.mprivozn@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 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 ebf446d966..725de736c1 100644

--- a/src/util/virdevmapper.c

+++ b/src/util/virdevmapper.c

@@ -49,11 +49,9 @@

 verify(BUF_SIZE > sizeof(struct dm_ioctl));

-static unsigned int virDMMajor;

-

 static int

-virDevMapperOnceInit(void)

+virDevMapperGetMajor(unsigned int *major)

 {

     VIR_AUTOFREE(char *) buf = NULL;

     VIR_AUTOSTRINGLIST lines = NULL;

@@ -72,7 +70,7 @@ virDevMapperOnceInit(void)

         if (sscanf(lines[i], "%u %ms\n", &maj, &dev) == 2 &&

             STREQ(dev, DM_NAME)) {

-            virDMMajor = maj;

+            *major = maj;

             break;

         }

     }

@@ -88,9 +86,6 @@ virDevMapperOnceInit(void)

 }

-VIR_ONCE_GLOBAL_INIT(virDevMapper)

-

-

 static void *

 virDMIoctl(int controlFD, int cmd, struct dm_ioctl *dm, char **buf)

 {

@@ -318,9 +313,6 @@ 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;

@@ -332,13 +324,14 @@ 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;

-- 

2.31.0