From: Karel Zak Subject: [PATCH] blkid: use /sys/block/dm-/dm/name Date: Mon, 27 Apr 2009 15:00:58 +0200 Message-ID: <1240837258-5440-2-git-send-email-kzak@redhat.com> References: <1240837258-5440-1-git-send-email-kzak@redhat.com> Cc: Eric Sandeen , Theodore Tso , Karel Zak , Milan Broz To: linux-ext4@vger.kernel.org Return-path: Received: from mx2.redhat.com ([66.187.237.31]:41727 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753346AbZD0NBK (ORCPT ); Mon, 27 Apr 2009 09:01:10 -0400 In-Reply-To: <1240837258-5440-1-git-send-email-kzak@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: The Linux kernel (since 2.6.29, patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) exports the real DM device names in /sys/block//dm/name. The sysfs based solution is nicer and faster than scan for devno in /dev/mapper/. CC: Milan Broz Signed-off-by: Karel Zak --- lib/blkid/devname.c | 28 +++++++++++++++++++++++++++- 1 files changed, 27 insertions(+), 1 deletions(-) diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c index 59c0919..4dde766 100644 --- a/lib/blkid/devname.c +++ b/lib/blkid/devname.c @@ -153,6 +153,30 @@ static int is_dm_leaf(const char *devname) } /* + * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs + * provides the real DM device names in /sys/block//dm/name + */ +static char *get_dm_name(const char *ptname) +{ + FILE *f; + size_t sz; + char path[256], name[256], *res = NULL; + + snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname); + if ((f = fopen(path, "r")) == NULL) + return NULL; + + /* read "\n" from sysfs */ + if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) { + name[sz - 1] = '\0'; + snprintf(path, sizeof(path), "/dev/mapper/%s", name); + res = blkid_strdup(path); + } + fclose(f); + return res; +} + +/* * Probe a single block device to add to the device cache. */ static void probe_one(blkid_cache cache, const char *ptname, @@ -183,7 +207,9 @@ static void probe_one(blkid_cache cache, const char *ptname, * to standard /dev/mapper/. */ if (!strncmp(ptname, "dm-", 3) && isdigit(ptname[3])) { - blkid__scan_dir("/dev/mapper", devno, 0, &devname); + devname = get_dm_name(ptname); + if (!devname) + blkid__scan_dir("/dev/mapper", devno, 0, &devname); if (devname) goto get_dev; } -- 1.6.0.6