The patch below does not apply to the 5.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 7e7986f9d3ba69a7375a41080a1f8c8012cb0923 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Tue, 1 Dec 2020 11:07:09 -0500
Subject: [PATCH] block: use gcd() to fix chunk_sectors limit stacking
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")
Reported-by: John Dorminy <jdorminy@xxxxxxxxxx>
Reported-by: Bruce Johnston <bjohnsto@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Reviewed-by: John Dorminy <jdorminy@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
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)) {
