From d5b58fbb2fd7ac25fcd7e1c14730f998a90b0322 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 16 Jun 2026 17:42:36 +0930 Subject: [PATCH] block: respect iov_iter::nofault flag in bio_iov_iter_bounce_write() 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 Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/9c165a314022b61566eb247852eb773ca6c70889.1781597506.git.wqu@suse.com Signed-off-by: Jens Axboe --- block/bio.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/bio.c b/block/bio.c index 96f40d39b62b..f2a5f4d0a967 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1335,7 +1335,11 @@ static int bio_iov_iter_bounce_write(struct bio *bio, struct iov_iter *iter, break; bio_add_folio_nofail(bio, folio, this_len, 0); - copied = copy_from_iter(folio_address(folio), this_len, iter); + if (iter->nofault) + copied = copy_folio_from_iter_atomic(folio, 0, this_len, + iter); + else + copied = copy_folio_from_iter(folio, 0, this_len, iter); if (copied < this_len) { /* * Need to revert the iov iter for all bytes we have