From: Sami Kerola <kerolasa@iki.fi>
Date: Wed, 5 Oct 2011 13:37:48 +0000 (+0200)
Subject: lsblk: inform about depencency to /sys/dev/block
X-Git-Tag: v2.21-rc1~349
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f65b3bb6257bb0885fd8bfe3bd6f0f4b2739d4b4;p=thirdparty%2Futil-linux.git

lsblk: inform about depencency to /sys/dev/block

The lsblk depends on /sys/dev/block/ symlinks, which appeared in
kernel 2.6.27.  Users with old, or non-sysfs configured, kernel
got ealier message

lsblk: md0: failed to initialize sysfs handler
lsblk: xvda: failed to initialize sysfs handler
[...]

that I found a little too difficult to understand.  This patch will
change the message to

lsblk: failed to access sysfs directory: /sys/dev/block: No such file or directory

and informs in manual page what could be reason to that.

[kzak@redhat.com: - use access() rather than opendir()]

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/misc-utils/lsblk.8 b/misc-utils/lsblk.8
index 72085ac28d..028b19f108 100644
--- a/misc-utils/lsblk.8
+++ b/misc-utils/lsblk.8
@@ -63,6 +63,15 @@ This option is equivalent to "-o NAME,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-SEC,RO
 .SH NOTES
 For the partitions are some information (e.g. queue attributes) inherited from
 parental device.
+.PP
+The
+.B lsblk
+needs to be able to lookup sysfs path by major:minor, which is done
+done by using
+.BR /sys/dev/block .
+The block sysfs appeared in kernel 2.6.27 (October 2008).  In case of
+problem with new enough kernel check that CONFIG_SYSFS was enabled at
+the time of kernel build.
 .SH AUTHORS
 .nf
 Milan Broz <mbroz@redhat.com>
diff --git a/misc-utils/lsblk.c b/misc-utils/lsblk.c
index f9c06fe075..74a1850878 100644
--- a/misc-utils/lsblk.c
+++ b/misc-utils/lsblk.c
@@ -947,6 +947,13 @@ errx_mutually_exclusive(const char *opts)
 	errx(EXIT_FAILURE, "%s %s", opts, _("options are mutually exclusive"));
 }
 
+static void check_sysdevblock(void)
+{
+	if (access(_PATH_SYS_DEVBLOCK, R_OK) != 0)
+		err(EXIT_FAILURE, _("failed to access sysfs directory: %s"),
+		    _PATH_SYS_DEVBLOCK);
+}
+
 int main(int argc, char *argv[])
 {
 	struct lsblk _ls;
@@ -1059,6 +1066,8 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	check_sysdevblock();
+
 	if (!ncolumns) {
 		columns[ncolumns++] = COL_NAME;
 		columns[ncolumns++] = COL_MAJMIN;