commit 22ada802ede8 ("block: use lcm_not_zero() when stacking
chunk_sectors") broke chunk_sectors limit stacking. chunk_sectors must
reflect the most limited of all devices in the IO stack.
Otherwise malformed IO may result. E.g.: prior to this fix,
->chunk_sectors = lcm_not_zero(8, 128) would result in
blk_max_size_offset() splitting IO at 128 sectors rather than the
required more restrictive 8 sectors.
And since commit 07d098e6bbad ("block: allow 'chunk_sectors' to be
non-power-of-2") care must be taken to properly stack chunk_sectors to
be compatible with the possibility that a non-power-of-2 chunk_sectors
may be stacked. This is why gcd() is used instead of reverting back
to using min_not_zero().
Fixes: 22ada802ede8 ("block: use lcm_not_zero() when stacking chunk_sectors")
Fixes: 07d098e6bbad ("block: allow 'chunk_sectors' to be non-power-of-2")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: John Dorminy <jdorminy@xxxxxxxxxx>
Reported-by: Bruce Johnston <bjohnsto@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
block/blk-settings.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
v2: use gcd(), instead of min_not_zero(), as suggested by John Dorminy
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 9741d1d83e98..659cdb8a07fe 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -547,7 +547,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->io_min = max(t->io_min, b->io_min);
t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
- t->chunk_sectors = lcm_not_zero(t->chunk_sectors, b->chunk_sectors);
+
+ /* Set non-power-of-2 compatible chunk_sectors boundary */
+ if (b->chunk_sectors)
+ t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
/* Physical block size a multiple of the logical block size? */
if (t->physical_block_size & (t->logical_block_size - 1)) {
--
2.15.0
--
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