N48

The fix makes me feel a little uneasy.

It changes the behaviour of swap_page_sector() to take into account the offset. But swap_page_sector() was already used before the bug was introduced, a few lines earlier in the bdev_write_page() fast path, as introduced by this commit from 2014: https://github.com/torvalds/linux/commit/dd6bd0d9c7dbb395100...

So either:

1. The bdev_write_page() call was also broken, and has been for years, or

2. The bdev_write_page() uses the sector value differently, worked fine with the old swap_page_sector(), but is now broken with the new version, or

3. The change in swap_page_sector() somehow doesn't affect bdev_write_page(); maybe it's a noop when using swap files?