block: don't silently ignore metadata for sync read/write

The block fops don't try to handle metadata for synchronous requests,
probably because the completion handler looks at dio->iocb which is not
valid for synchronous requests.

But silently ignoring metadata (or warning in case of
__blkdev_direct_IO_simple) is a really bad idea as that can cause
silent data corruption if a user ever shows up.

Instead simply handle metadata for synchronous requests as the completion
handler can simply check for bio_integrity() as the block layer default
integrity will already be freed at this point, and thus bio_integrity()
will only return true for user mapped integrity.

Fixes: 3d8b5a22 ("block: add support to pass user meta buffer")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/20250819082517.2038819-3-hch@lst.de


Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>