md/raid6: use valid sector values to determine if an I/O should wait on the reshape
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: 486f6055 ("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
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