6.1-stable review patch. If anyone has any objections, please let me know.
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From: David Jeffery djeffery@redhat.com
commit c467e97f079f0019870c314996fae952cc768e82 upstream.
During a reshape or a RAID6 array such as expanding by adding an additional disk, I/Os to the region of the array which have not yet been reshaped can stall indefinitely. This is from errors in the stripe_ahead_of_reshape function causing md to think the I/O is to a region in the actively undergoing the reshape.
stripe_ahead_of_reshape fails to account for the q disk having a sector value of 0. By not excluding the q disk from the for loop, raid6 will always generate a min_sector value of 0, causing a return value which stalls.
The function's max_sector calculation also uses min() when it should use max(), causing the max_sector value to always be 0. During a backwards rebuild this can cause the opposite problem where it allows I/O to advance when it should wait.
Fixing these errors will allow safe I/O to advance in a timely manner and delay only I/O which is unsafe due to stripes in the middle of undergoing the reshape.
Fixes: 486f60558607 ("md/raid5: Check all disks in a stripe_head for reshape progress") Cc: stable@vger.kernel.org # v6.0+ Signed-off-by: David Jeffery djeffery@redhat.com Tested-by: Laurence Oberman loberman@redhat.com Signed-off-by: Song Liu song@kernel.org Link: https://lore.kernel.org/r/20231128181233.6187-1-djeffery@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/raid5.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -5905,11 +5905,11 @@ static bool stripe_ahead_of_reshape(stru int dd_idx;
for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) { - if (dd_idx == sh->pd_idx) + if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx) continue;
min_sector = min(min_sector, sh->dev[dd_idx].sector); - max_sector = min(max_sector, sh->dev[dd_idx].sector); + max_sector = max(max_sector, sh->dev[dd_idx].sector); }
spin_lock_irq(&conf->device_lock);