[PATCH v1 03/14] mm: add noio support in filemap_get_pages

[Stefan Roesch <shr@fb.com>]

This adds noio support for async buffered writes in filemap_get_pages.
The idea is to handle the failure gracefully and return -EAGAIN if we
can't get the memory quickly.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 mm/filemap.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index d2fb817c0845..0ff4278c3961 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2591,10 +2591,15 @@ static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
 		filemap_get_read_batch(mapping, index, last_index, fbatch);
 	}
 	if (!folio_batch_count(fbatch)) {
+		unsigned int pflags;
+
 		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
-			return -EAGAIN;
+			pflags = memalloc_noio_save();
 		err = filemap_create_folio(filp, mapping,
 				iocb->ki_pos >> PAGE_SHIFT, fbatch);
+		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
+			memalloc_noio_restore(pflags);
+
 		if (err == AOP_TRUNCATED_PAGE)
 			goto retry;
 		return err;
-- 
2.30.2