For the incoming usage of IOMAP_DIO_BOUNCE in btrfs, btrfs has set
iov_iter::nofault to prevent deadlock when a page fault is needed to
read out the buffer.
However bio_iov_iter_bounce_write() doesn't respect iov_iter::nofault
flag, and just call a plain copy_from_iter() so it can still trigger
page fault and cause deadlock in btrfs.
Fix it by utilizing copy_folio_from_iter_atomic() if nofault flag is
set, otherwise use copy_folio_from_iter().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/9c165a314022b61566eb247852eb773ca6c70889.1781597506.git.wqu@suse.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
d5b58fbb2f