On 13/02/2024 09:36, Nilay Shroff wrote:
+static bool blkdev_atomic_write_valid(struct block_device *bdev, loff_t pos,
+ struct iov_iter *iter)
+{
+ struct request_queue *q = bdev_get_queue(bdev);
+ unsigned int min_bytes = queue_atomic_write_unit_min_bytes(q);
+ unsigned int max_bytes = queue_atomic_write_unit_max_bytes(q);
+
+ if (!iter_is_ubuf(iter))
+ return false;
+ if (iov_iter_count(iter) & (min_bytes - 1))
+ return false;
+ if (!is_power_of_2(iov_iter_count(iter)))
+ return false;
+ if (pos & (iov_iter_count(iter) - 1))
+ return false;
+ if (iov_iter_count(iter) > max_bytes)
+ return false;
+ return true;
+}
Here do we need to also validate whether the IO doesn't straddle
the atmic bondary limit (if it's non-zero)? We do check that IO
doesn't straddle the atomic boundary limit but that happens very
late in the IO code path either during blk-merge or in NVMe driver
code.
It's relied that atomic_write_unit_max is <= atomic_write_boundary and
both are a power-of-2. Please see the NVMe patch, which this is checked.
Indeed, it would not make sense if atomic_write_unit_max >
atomic_write_boundary (when non-zero).
So if the write is naturally aligned and its size is <=
atomic_write_unit_max, then it cannot be straddling a boundary.
Thanks,
John
