From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Rajnoha Date: Mon, 07 Nov 2011 13:49:23 +0100 Subject: [PATCH 1/2] dev names: Add dm_device_get_name to acquire device name for given major:minor pair Message-ID: <4EB7D3D3.1030507@redhat.com> List-Id: To: lvm-devel@redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit The code to acquire device's kernel name using sysfs is already upstream, this is just a tiny refactor that exports this functionality as libdevmapper fn. In addition, it adds a possibility to read the device-mapper name from sysfs using given major:minor pair (which is a quick operation). The new fn "int dm_device_get_name(uint32_t major, uint32_t minor, int prefer_kernel_name, char *buf, size_t buf_size)" has a "pefer_kernel_name" switch with which it's possible to prefer kernel "dm-X" names over device-mapper names if this is a device-mapper device (for non-dm devices, only kernel name is possible). Note: Since the /sys/block/major:minor/dm/name item was added later (kernel 2.6.29 iirc), there's a fallback to return kernel "dm-X" name if we're not able to get the dm name via sysfs (with some log_debug in place). Peter --- libdm/libdevmapper.h | 9 ++++ libdm/libdm-common.c | 122 ++++++++++++++++++++++++++++++++++++++++--------- 2 files changed, 108 insertions(+), 23 deletions(-) diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h index c865f6f..d71d61e 100644 --- a/libdm/libdevmapper.h +++ b/libdm/libdevmapper.h @@ -267,6 +267,15 @@ const char *dm_sysfs_dir(void); int dm_is_dm_major(uint32_t major); /* + * Get device name for given major and minor number. If prefer_kernel_name + * is set, kernel name is preferred over dm name for dm devices. If sysfs + * is not used (or configured incorrectly), returns 0. + */ +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. diff --git a/libdm/libdm-common.c b/libdm/libdm-common.c index 23539d7..5b9ba0b 100644 --- a/libdm/libdm-common.c +++ b/libdm/libdm-common.c @@ -1056,6 +1056,103 @@ const char *dm_sysfs_dir(void) return _sysfs_dir; } +static int _sysfs_get_dm_name(uint32_t major, uint32_t minor, char *buf, size_t buf_size) +{ + char sysfs_path[PATH_MAX]; + char temp_buf[PATH_MAX]; + FILE *fp; + + 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"); + return 0; + } + + if (!(fp = fopen(sysfs_path, "r"))) { + if (errno != ENOENT) + log_sys_error("fopen", sysfs_path); + else + log_sys_debug("fopen", sysfs_path); + return 0; + } + + if (!fgets(temp_buf, sizeof(temp_buf), fp)) { + log_sys_debug("fgets", sysfs_path); + return 0; + } + 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: output buffer too small"); + return 0; + } + + strcpy(buf, temp_buf); + return 1; +} + +static int _sysfs_get_kernel_name(uint32_t major, uint32_t minor, char *buf, size_t buf_size) +{ + char sysfs_path[PATH_MAX]; + char temp_buf[PATH_MAX]; + ssize_t size; + char *name; + + if (dm_snprintf(sysfs_path, PATH_MAX, "%sdev/block/%" PRIu32 ":%" PRIu32, + _sysfs_dir, major, minor) < 0) { + log_error("_sysfs_get_kerne_name: dm_snprintf failed"); + return 0; + } + + 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); + return 0; + } + temp_buf[size] = '\0'; + + if (!(name = strrchr(temp_buf, '/'))) { + log_error("Could not locate device kernel name in sysfs path %s", temp_buf); + return 0; + } + name += 1; + + if (buf_size < strlen(name) + 1) { + log_error("_sysfs_get_kernel_name: output buffer too small"); + return 0; + } + + strcpy(buf, name); + return 1; +} + +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 && + _sysfs_get_dm_name(major, minor, buf, buf_size)) + return 1; + + /* + * 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]; @@ -1126,32 +1223,11 @@ static int _mounted_fs_on_device(const char *kernel_dev_name) 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// presence */ return _mounted_fs_on_device(kernel_dev_name);