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Use hard-coded /dev/mapper/control details for 2.6.36+ kernels and simplify

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associated code.  (Some obscure configurations that happened to work before
are no longer supported.)
This commit is contained in:
Alasdair Kergon 2011-03-25 23:50:35 +00:00
parent be226be635
commit 76c13d16eb
2 changed files with 32 additions and 62 deletions
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2
WHATS_NEW_DM
View File

@ -1,5 +1,7 @@
Version 1.02.64 -
===================================
Streamline /dev/mapper/control node code for common cases.
Use hard-coded dm control node device number for 2.6.36 kernels and above.
Improve stack debug reporting in dm_task_create().
Fallback to control node creation only if node doesn't exist yet.
Change dm_hash API for binary data to accept const void *key.

92
libdm/ioctl/libdm-iface.c
View File

@ -228,7 +228,7 @@ static int _control_device_number(uint32_t *major, uint32_t *minor)
}
/*
* Returns 1 if exists; 0 if it doesn't; -1 if it's wrong
* Returns 1 if it exists on returning; 0 if it doesn't; -1 if it's wrong.
*/
static int _control_exists(const char *control, uint32_t major, uint32_t minor)
{
@ -267,8 +267,15 @@ static int _create_control(const char *control, uint32_t major, uint32_t minor)
int ret;
mode_t old_umask;
if (!major)
return 0;
/*
* Return if the control already exists with intended major/minor
* or there's an error unlinking an apparently incorrect one.
*/
ret = _control_exists(control, major, minor);
if (ret == -1)
return 0; /* Failed to unlink existing incorrect node */
if (ret)
return 1; /* Already exists and correct */
(void) dm_prepare_selinux_context(dm_dir(), S_IFDIR);
old_umask = umask(DM_DEV_DIR_UMASK);
@ -359,14 +366,9 @@ static void _close_control_fd(void)
}
}
static int _open_and_assign_control_fd(const char *control,
int ignore_nodev)
static int _open_and_assign_control_fd(const char *control)
{
_close_control_fd();
if ((_control_fd = open(control, O_RDWR)) < 0) {
if (ignore_nodev && errno == ENODEV)
return 1;
log_sys_error("open", control);
return 0;
}
@ -378,8 +380,8 @@ static int _open_control(void)
{
#ifdef DM_IOCTLS
char control[PATH_MAX];
uint32_t major = 0, minor;
int dm_mod_autoload_support, needs_open;
uint32_t major = MISC_MAJOR;
uint32_t minor = MAPPER_CTRL_MINOR;
if (_control_fd != -1)
return 1;
@ -390,63 +392,27 @@ static int _open_control(void)
snprintf(control, sizeof(control), "%s/%s", dm_dir(), DM_CONTROL_NODE);
/*
* dm-mod autoloading is supported since kernel 2.6.36.
* Udev daemon will try to read modules.devname file extracted
* by depmod and create any static nodes needed.
* The /dev/mapper/control node can be created and prepared this way.
* First access to such node should load dm-mod module automatically.
* Prior to 2.6.36 the minor number should be looked up in /proc.
*/
dm_mod_autoload_support = KERNEL_VERSION(_kernel_major, _kernel_minor,
_kernel_release) >= KERNEL_VERSION(2, 6, 36);
if ((KERNEL_VERSION(_kernel_major, _kernel_minor, _kernel_release) <
KERNEL_VERSION(2, 6, 36)) &&
!_control_device_number(&major, &minor))
goto_bad;
/*
* If dm-mod autoloading is supported and the control node exists
* already try to open it now. This should autoload dm-mod module.
* Create the node with correct major and minor if not already done.
* Udev may already have created /dev/mapper/control
* from the modules.devname file generated by depmod.
*/
if (dm_mod_autoload_support) {
if (!_get_proc_number(PROC_DEVICES, MISC_NAME, &major))
/* If major not found, just fallback to hardcoded value. */
major = MISC_MAJOR;
/* Recreate the node with correct major and minor if needed. */
if (!_control_exists(control, major, MAPPER_CTRL_MINOR) &&
!_create_control(control, major, MAPPER_CTRL_MINOR))
goto error;
/* Fallback to old code only if control node doesn't exist */
if (!_open_and_assign_control_fd(control, 1))
goto error;
}
if (!_create_control(control, major, minor))
goto_bad;
/*
* Get major and minor number assigned for the control node.
* In case we make use of the module autoload support, this
* information should be accessible now as well.
* As of 2.6.36 kernels, the open can trigger autoloading dm-mod.
*/
if (!_control_device_number(&major, &minor))
log_error("Is device-mapper driver missing from kernel?");
/*
* Check the control node and its major and minor number.
* If there's anything wrong, remove the old node and create
* a correct one.
*/
if ((needs_open = !_control_exists(control, major, minor)) &&
!_create_control(control, major, minor)) {
_close_control_fd();
goto error;
}
/*
* For older kernels without dm-mod autoloading support, we always
* need to open the control node here - we still haven't done that!
* For newer kernels with dm-mod autoloading, we open it only if the
* node was recreated and corrected in previous step.
*/
if ((!dm_mod_autoload_support || needs_open) &&
!_open_and_assign_control_fd(control, 0))
goto error;
if (!_open_and_assign_control_fd(control))
goto_bad;
if (!_create_dm_bitset()) {
log_error("Failed to set up list of device-mapper major numbers");
return 0;
@ -454,8 +420,10 @@ static int _open_control(void)
return 1;
error:
bad:
log_error("Failure to communicate with kernel device-mapper driver.");
if (!geteuid())
log_error("Check that device-mapper is available in the kernel.");
return 0;
#else
return 1;