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block: respect iov_iter::nofault flag in bio_iov_iter_bounce_write()

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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>
This commit is contained in:
Qu Wenruo 2026-06-16 17:42:36 +09:30 committed by Jens Axboe
parent b68d4979c8
commit d5b58fbb2f
1 changed files with 5 additions and 1 deletions
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6
block/bio.c
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@ -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