fstests: add helper to canonicalize devices used to enable persistent disks

The filesystem configuration file does not allow you to use symlinks to
real devices given the existing sanity checks verify that the target end
device matches the source. Device mapper links work but not symlinks for
real drives do not.

Using a symlink is desirable if you want to enable persistent tests
across reboots. For example you may want to use /dev/disk/by-id/nvme-eui.*
so to ensure that the same drives are used even after reboot. This
is very useful if you are testing for example with a virtualized
environment and are using PCIe passthrough with other qemu NVMe drives
with one or many NVMe drives.

To enable support just add a helper to canonicalize devices prior to
running the tests.

This allows one test runner, kdevops, which I just extended with
support to use real NVMe drives it has support now to use nvme EUI
symlinks and fallbacks to nvme model + serial symlinks as not all
NVMe drives support EUIs. The drives it uses for the filesystem
configuration optionally is with NVMe eui symlinks so to allow
the same drives to be used over reboots.

For instance this works today with real nvme drives:

mkfs.xfs -f /dev/nvme0n1
mount /dev/nvme0n1 /mnt
TEST_DIR=/mnt TEST_DEV=/dev/nvme0n1 FSTYP=xfs ./check generic/110

FSTYP         -- xfs (debug)
PLATFORM      -- Linux/x86_64 flax-mtr01 6.5.0-rc3-djwx #rc3 SMP PREEMPT_DYNAMIC Wed Jul 26 14:26:48 PDT 2023

generic/110        2s
Ran: generic/110
Passed all 1 tests

But this does not:

TEST_DIR=/mnt TEST_DEV=/dev/disk/by-id/nvme-eui.0035385411904c1e FSTYP=xfs ./check generic/110
mount: /mnt: /dev/disk/by-id/nvme-eui.0035385411904c1e already mounted on /mnt.
common/rc: retrying test device mount with external set
mount: /mnt: /dev/disk/by-id/nvme-eui.0035385411904c1e already mounted on /mnt.
common/rc: could not mount /dev/disk/by-id/nvme-eui.0035385411904c1e on /mnt

umount /mnt
TEST_DIR=/mnt TEST_DEV=/dev/disk/by-id/nvme-eui.0035385411904c1e FSTYP=xfs ./check generic/110
TEST_DEV=/dev/disk/by-id/nvme-eui.0035385411904c1e is mounted but not on TEST_DIR=/mnt - aborting
Already mounted result:
/dev/disk/by-id/nvme-eui.0035385411904c1e /mnt

This fixes this. This allows the same real drives for a test to be
used over and over after reboots.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

3 files changed, 35 insertions, 1 deletions

diff --git a/README b/README
index ccfdcbe703..d9db96755a 100644
--- a/README
+++ b/README
@@ -285,6 +285,9 @@ Misc:
  - Set REPORT_VARS_FILE to a file containing colon-separated name-value pairs
    that will be recorded in the test section report.  Names must be unique.
    Whitespace surrounding the colon will be removed.
+ - set CANON_DEVS=yes to canonicalize device symlinks. This will let you
+   for example use something like TEST_DEV/dev/disk/by-id/nvme-* so the
+   device remains persistent between reboots. This is disabled by default.
 
 ______________________
 USING THE FSQA SUITE
diff --git a/check b/check
index 287cd8955e..549725eb8d 100755
--- a/check
+++ b/check
@@ -751,6 +751,7 @@ function run_section()
 	fi
 
 	get_next_config $section
+	_canonicalize_devices
 
 	mkdir -p $RESULT_BASE
 	if [ ! -d $RESULT_BASE ]; then
diff --git a/common/config b/common/config
index 936ac225f4..c9771ff934 100644
--- a/common/config
+++ b/common/config
@@ -25,6 +25,9 @@
 # KEEP_DMESG -      whether to keep all dmesg for each test case.
 #                   yes: keep all dmesg
 #                   no: only keep dmesg with error/warning (default)
+# CANON_DEVS -      whether or not to canonicalize device symlinks
+#                   yes: canonicalize device symlinks
+#                   no (default) do not canonicalize device if they are symlinks
 #
 # - These can be added to $HOST_CONFIG_DIR (witch default to ./config)
 #   below or a separate local configuration file can be used (using
@@ -655,6 +658,32 @@ _canonicalize_mountpoint()
 	echo "$parent/$base"
 }
 
+# Enables usage of /dev/disk/by-id/ symlinks to persist target devices
+# over reboots
+_canonicalize_devices()
+{
+	if [ "$CANON_DEVS" != "yes" ]; then
+		return
+	fi
+	[ -L "$TEST_DEV" ]	&& TEST_DEV=$(readlink -e "$TEST_DEV")
+	[ -L "$SCRATCH_DEV" ]	&& SCRATCH_DEV=$(readlink -e "$SCRATCH_DEV")
+	[ -L "$TEST_LOGDEV" ]	&& TEST_LOGDEV=$(readlink -e "$TEST_LOGDEV")
+	[ -L "$TEST_RTDEV" ]	&& TEST_RTDEV=$(readlink -e "$TEST_RTDEV")
+	[ -L "$SCRATCH_RTDEV" ]	&& SCRATCH_RTDEV=$(readlink -e "$SCRATCH_RTDEV")
+	[ -L "$LOGWRITES_DEV" ]	&& LOGWRITES_DEV=$(readlink -e "$LOGWRITES_DEV")
+	if [ ! -z "$SCRATCH_DEV_POOL" ]; then
+		local NEW_SCRATCH_POOL=""
+		for i in $SCRATCH_DEV_POOL; do
+			if [ -L $i ]; then
+				NEW_SCRATCH_POOL="$NEW_SCRATCH_POOL $(readlink -e $i)"
+			else
+				NEW_SCRATCH_POOL="$NEW_SCRATCH_POOL $i)"
+			fi
+		done
+		SCRATCH_DEV_POOL="$NEW_SCRATCH_POOL"
+	fi
+}
+
 # On check -overlay, for the non multi section config case, this
 # function is called on every test, before init_rc().
 # When SCRATCH/TEST_* vars are defined in config file, config file
@@ -785,7 +814,6 @@ get_next_config() {
 	fi
 
 	parse_config_section $1
-
 	if [ ! -z "$OLD_FSTYP" ] && [ $OLD_FSTYP != $FSTYP ]; then
 		[ -z "$MOUNT_OPTIONS" ] && _mount_opts
 		[ -z "$TEST_FS_MOUNT_OPTS" ] && _test_mount_opts
@@ -901,5 +929,7 @@ else
 	fi
 fi
 
+_canonicalize_devices
+
 # make sure this script returns success
 /bin/true