The atomic write unit max is limited by any stack device stripe size. It is required that the atomic write unit is a power-of-2 factor of the stripe size.
Currently we use io_min limit to hold the stripe size, and check for a io_min <= SECTOR_SIZE when deciding if we have a striped stacked device. Nilay reports that this causes a problem when the physical block size is greater than SECTOR_SIZE [0]. Furthermore, io_min may be mutated when stacking devices, and this makes it a poor candidate to hold the stripe size. Such an example would be when the io_min is less than the physical block size. Use chunk_sectors to hold the stripe size, which is more appropriate. [0] https://lore.kernel.org/linux-block/888f3b1d-7817-4007-b3b3-1a2ea04df...@linux.ibm.com/T/#mecca17129f72811137d3c2f1e477634e77f06781 Signed-off-by: John Garry <john.g.ga...@oracle.com> --- block/blk-settings.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/block/blk-settings.c b/block/blk-settings.c index a000daafbfb4..5b0f1a854e81 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -594,11 +594,13 @@ static bool blk_stack_atomic_writes_boundary_head(struct queue_limits *t, static bool blk_stack_atomic_writes_head(struct queue_limits *t, struct queue_limits *b) { + unsigned int chunk_size = t->chunk_sectors << SECTOR_SHIFT; + if (b->atomic_write_hw_boundary && !blk_stack_atomic_writes_boundary_head(t, b)) return false; - if (t->io_min <= SECTOR_SIZE) { + if (!t->chunk_sectors) { /* No chunk sectors, so use bottom device values directly */ t->atomic_write_hw_unit_max = b->atomic_write_hw_unit_max; t->atomic_write_hw_unit_min = b->atomic_write_hw_unit_min; @@ -617,12 +619,12 @@ static bool blk_stack_atomic_writes_head(struct queue_limits *t, * aligned with both limits, i.e. 8K in this example. */ t->atomic_write_hw_unit_max = b->atomic_write_hw_unit_max; - while (t->io_min % t->atomic_write_hw_unit_max) + while (chunk_size % t->atomic_write_hw_unit_max) t->atomic_write_hw_unit_max /= 2; t->atomic_write_hw_unit_min = min(b->atomic_write_hw_unit_min, t->atomic_write_hw_unit_max); - t->atomic_write_hw_max = min(b->atomic_write_hw_max, t->io_min); + t->atomic_write_hw_max = min(b->atomic_write_hw_max, chunk_size); return true; } -- 2.31.1
