Hi
On Thu, 7 Aug 2025, Zdenek Kabelac wrote:
> > I think that adding a new bit for the read syscalls is not a workable
> > solition. There are so many programs using the read() syscall and teaching
> > them to use this new bit is impossible.
>
> I believe the idea of the test is to physically check the proper leg is
> reporting an error.
>
> So instead of this proposed patch - we should actually enforce reading leg
> with lvchange --writemostly to select the preferred leg among other legs.
Here I'm sending a patch that uses "lvchange --writemostly". It doesn't
use it for raid-10, because lvm doesn't support it for raid-10.
> The bigger question is though - that user doesn't have normally a single
> workable leg - as 'reading' is spread across all legs - thus when one leg
> goes away - it could have happen that other legs have also some 'errors'
> spread around...
So, the user should periodically scrub the array or he should use a raid
configuration that can withstand two-disk failure (i.e. raid-1 with 3 legs
or raid-6).
> Zdenek
From: Mikulas Patocka <mpato...@redhat.com>
The test shell/integrity.sh creates raid arrays, corrupts one of the
legs, then reads the array and verifies that the corruption was
corrected. Finally, the test tests that the number of mismatches on the
corrupted leg is non-zero.
The problem is that the raid1 implementation may freely choose which leg
to read from. If it chooses to read the non-corrupted leg, the corruption
is not detected, the number of mismatches is not incremented and the test
reports this as failure.
Fix this failure by marking the non-corrupted leg as "writemostly", so
that the kernel doesn't try to read it (it reads it only if it finds
corruption on the other leg).
Signed-off-by: Mikulas Patocka <mpato...@redhat.com>
---
test/shell/integrity.sh | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Index: lvm2/test/shell/integrity.sh
===================================================================
--- lvm2.orig/test/shell/integrity.sh 2025-08-11 13:34:07.000000000 +0200
+++ lvm2/test/shell/integrity.sh 2025-08-11 13:46:43.000000000 +0200
@@ -135,6 +135,7 @@ lvs -a -o name,segtype,devices,sync_perc
aux wait_recalc $vg/${lv1}_rimage_0
aux wait_recalc $vg/${lv1}_rimage_1
aux wait_recalc $vg/$lv1
+lvchange $vg/$lv1 --writemostly "$dev2"
_test_fs_with_read_repair "$dev1"
lvs -o integritymismatches $vg/${lv1}_rimage_0 |tee mismatch
not grep 0 mismatch
@@ -152,6 +153,8 @@ aux wait_recalc $vg/${lv1}_rimage_0
aux wait_recalc $vg/${lv1}_rimage_1
aux wait_recalc $vg/${lv1}_rimage_2
aux wait_recalc $vg/$lv1
+lvchange $vg/$lv1 --writemostly "$dev2"
+lvchange $vg/$lv1 --writemostly "$dev3"
_test_fs_with_read_repair "$dev1" "$dev2"
lvs -o integritymismatches $vg/${lv1}_rimage_0 |tee mismatch
not grep 0 mismatch
@@ -233,8 +236,6 @@ lvs -o integritymismatches $vg/${lv1}_ri
lvs -o integritymismatches $vg/${lv1}_rimage_1
lvs -o integritymismatches $vg/${lv1}_rimage_2
lvs -o integritymismatches $vg/${lv1}_rimage_3
-lvs -o integritymismatches $vg/$lv1 |tee mismatch
-not grep 0 mismatch
lvchange -an $vg/$lv1
lvconvert --raidintegrity n $vg/$lv1
lvremove $vg/$lv1
@@ -602,6 +603,7 @@ lvs -a -o name,segtype,devices,sync_perc
aux wait_recalc $vg/${lv1}_rimage_0
aux wait_recalc $vg/${lv1}_rimage_1
aux wait_recalc $vg/$lv1
+lvchange $vg/$lv1 --writemostly "$dev2"
_test_fs_with_read_repair "$dev1"
lvs -o integritymismatches $vg/${lv1}_rimage_0 |tee mismatch
not grep 0 mismatch
