[lvm-devel] LVM2 ./WHATS_NEW_DM libdm/libdevmapper.h libdm ...
prajnoha at sourceware.org
prajnoha at sourceware.org
Wed Jan 11 12:34:48 UTC 2012
CVSROOT: /cvs/lvm2
Module name: LVM2
Changes by: prajnoha at sourceware.org 2012-01-11 12:34:45
Modified files:
. : WHATS_NEW_DM
libdm : libdevmapper.h libdm-common.c
Log message:
Add dm_device_get_name to get map name or block device name for given devno.
This is accomplished by reading associated sysfs information. For a dm device,
this is /sys/dev/block/major:minor/dm/name (supported in kernel version >= 2.6.29,
for older kernels, the behaviour is the same as for non-dm devices).
For a non-dm device, this is a readlink on /sys/dev/block/major:minor, e.g.
/sys/dev/block/253:0 --> ../../devices/virtual/block/dm-0.
The last component of the path is a proper kernel name (block device name).
One can request to read only kernel names by setting the 'prefer_kernel_name'
argument if needed.
Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/WHATS_NEW_DM.diff?cvsroot=lvm2&r1=1.529&r2=1.530
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/libdm/libdevmapper.h.diff?cvsroot=lvm2&r1=1.174&r2=1.175
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/libdm/libdm-common.c.diff?cvsroot=lvm2&r1=1.131&r2=1.132
--- LVM2/WHATS_NEW_DM 2012/01/10 02:03:31 1.529
+++ LVM2/WHATS_NEW_DM 2012/01/11 12:34:44 1.530
@@ -1,5 +1,6 @@
Version 1.02.68 -
==================================
+ Add dm_device_get_name to get map name or block device name for given devno.
Remove empty devices when clearing left-over inactive tables in deptree.
Add dm_uuid_prefix/dm_set_uuid_prefix to override hard-coded LVM- prefix.
Improve dmsetup man page about readahead parameter.
--- LVM2/libdm/libdevmapper.h 2012/01/10 02:03:32 1.174
+++ LVM2/libdm/libdevmapper.h 2012/01/11 12:34:45 1.175
@@ -300,6 +300,21 @@
int dm_is_dm_major(uint32_t major);
/*
+ * Get associated device name for given major and minor number by reading
+ * the sysfs content. If this is a dm device, get associated dm name, the one
+ * that appears in /dev/mapper. DM names could be resolved this way only if
+ * kernel used >= 2.6.29, kernel name is found otherwise (e.g. dm-0).
+ * If prefer_kernel_name is set, the kernel name is always preferred over
+ * device-mapper name for dm devices no matter what the kernel version is.
+ * For non-dm devices, we always get associated kernel name, e.g sda, md0 etc.
+ * Returns 0 on error or if sysfs is not used (or configured incorrectly),
+ * otherwise returns 1 and the supplied buffer holds the device name.
+ */
+int dm_device_get_name(uint32_t major, uint32_t minor,
+ int prefer_kernel_name,
+ char *buf, size_t buf_size);
+
+/*
* Determine whether a device has any holders (devices
* using this device). If sysfs is not used (or configured
* incorrectly), returns 0.
--- LVM2/libdm/libdm-common.c 2012/01/10 02:03:32 1.131
+++ LVM2/libdm/libdm-common.c 2012/01/11 12:34:45 1.132
@@ -1165,6 +1165,133 @@
return _default_uuid_prefix;
}
+static int _sysfs_get_dm_name(uint32_t major, uint32_t minor, char *buf, size_t buf_size)
+{
+ char *sysfs_path, *temp_buf;
+ FILE *fp;
+
+ if (!(sysfs_path = dm_malloc(PATH_MAX)) ||
+ !(temp_buf = dm_malloc(PATH_MAX))) {
+ log_error("_sysfs_get_dm_name: failed to allocate temporary buffers");
+ if (sysfs_path)
+ dm_free(sysfs_path);
+ return 0;
+ }
+
+ if (dm_snprintf(sysfs_path, PATH_MAX, "%sdev/block/%" PRIu32 ":%" PRIu32
+ "/dm/name", _sysfs_dir, major, minor) < 0) {
+ log_error("_sysfs_get_dm_name: dm_snprintf failed");
+ goto error;
+ }
+
+ if (!(fp = fopen(sysfs_path, "r"))) {
+ if (errno != ENOENT)
+ log_sys_error("fopen", sysfs_path);
+ else
+ log_sys_debug("fopen", sysfs_path);
+ goto error;
+ }
+
+ if (!fgets(temp_buf, PATH_MAX, fp)) {
+ log_sys_error("fgets", sysfs_path);
+ goto error;
+ }
+ temp_buf[strlen(temp_buf) - 1] = '\0';
+
+ if (fclose(fp))
+ log_sys_error("fclose", sysfs_path);
+
+ if (buf_size < strlen(temp_buf) + 1) {
+ log_error("_sysfs_get_dm_name: supplied buffer too small");
+ goto error;
+ }
+
+ strncpy(buf, temp_buf, buf_size);
+ dm_free(sysfs_path);
+ dm_free(temp_buf);
+ return 1;
+
+error:
+ dm_free(sysfs_path);
+ dm_free(temp_buf);
+ return 0;
+}
+
+static int _sysfs_get_kernel_name(uint32_t major, uint32_t minor, char *buf, size_t buf_size)
+{
+ char *sysfs_path, *temp_buf, *name;
+ ssize_t size;
+
+ if (!(sysfs_path = dm_malloc(PATH_MAX)) ||
+ !(temp_buf = dm_malloc(PATH_MAX))) {
+ log_error("_sysfs_get_kernel_name: failed to allocate temporary buffers");
+ if (sysfs_path)
+ dm_free(sysfs_path);
+ return 0;
+ }
+
+ if (dm_snprintf(sysfs_path, PATH_MAX, "%sdev/block/%" PRIu32 ":%" PRIu32,
+ _sysfs_dir, major, minor) < 0) {
+ log_error("_sysfs_get_kernel_name: dm_snprintf failed");
+ goto error;
+ }
+
+ if ((size = readlink(sysfs_path, temp_buf, PATH_MAX)) < 0) {
+ if (errno != ENOENT)
+ log_sys_error("readlink", sysfs_path);
+ else
+ log_sys_debug("readlink", sysfs_path);
+ goto error;
+ }
+ temp_buf[size] = '\0';
+
+ if (!(name = strrchr(temp_buf, '/'))) {
+ log_error("Could not locate device kernel name in sysfs path %s", temp_buf);
+ goto error;
+ }
+ name += 1;
+
+ if (buf_size < strlen(name) + 1) {
+ log_error("_sysfs_get_kernel_name: output buffer too small");
+ goto error;
+ }
+
+ strncpy(buf, name, buf_size);
+ dm_free(sysfs_path);
+ dm_free(temp_buf);
+ return 1;
+
+error:
+ dm_free(sysfs_path);
+ dm_free(temp_buf);
+ return 0;
+}
+
+int dm_device_get_name(uint32_t major, uint32_t minor, int prefer_kernel_name,
+ char *buf, size_t buf_size)
+{
+ if (!*_sysfs_dir)
+ return 0;
+
+ /*
+ * device-mapper devices and prefer_kernel_name = 0
+ * get dm name by reading /sys/dev/block/major:minor/dm/name,
+ * fallback to _sysfs_get_kernel_name if not successful
+ */
+ if (dm_is_dm_major(major) && !prefer_kernel_name) {
+ if (_sysfs_get_dm_name(major, minor, buf, buf_size))
+ return 1;
+ else
+ stack;
+ }
+
+ /*
+ * non-device-mapper devices or prefer_kernel_name = 1
+ * get kernel name using readlink /sys/dev/block/major:minor -> .../dm-X
+ */
+ return _sysfs_get_kernel_name(major, minor, buf, buf_size);
+}
+
int dm_device_has_holders(uint32_t major, uint32_t minor)
{
char sysfs_path[PATH_MAX];
@@ -1235,32 +1362,11 @@
int dm_device_has_mounted_fs(uint32_t major, uint32_t minor)
{
- char sysfs_path[PATH_MAX];
- char temp_path[PATH_MAX];
- char *kernel_dev_name;
- ssize_t size;
-
- if (!*_sysfs_dir)
- return 0;
+ char kernel_dev_name[PATH_MAX];
/* Get kernel device name first */
- if (dm_snprintf(sysfs_path, PATH_MAX, "%sdev/block/%" PRIu32 ":%" PRIu32,
- _sysfs_dir, major, minor) < 0) {
- log_error("sysfs_path dm_snprintf failed");
- return 0;
- }
-
- if ((size = readlink(sysfs_path, temp_path, PATH_MAX)) < 0) {
- log_sys_error("readlink", sysfs_path);
+ if (!dm_device_get_name(major, minor, 1, kernel_dev_name, PATH_MAX))
return 0;
- }
- temp_path[size] = '\0';
-
- if (!(kernel_dev_name = strrchr(temp_path, '/'))) {
- log_error("Could not locate device kernel name in sysfs path %s", temp_path);
- return 0;
- }
- kernel_dev_name += 1;
/* Check /sys/fs/<fs_name>/<kernel_dev_name> presence */
return _mounted_fs_on_device(kernel_dev_name);
More information about the lvm-devel
mailing list