block: only restrict bio allocation gfp mask asked to block

If the caller is asking for a non-blocking allocation, we should not
further restrict the gfp mask, which just increases the likelihood
of failures.

Fixes: b520c4e ("block: split bio_alloc_bioset more clearly into a fast and slowpath")
Reported-by: Shin'ichiro Kawasaki <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Bart Van Assche <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

block/bio.c

@@ -544,7 +544,8 @@ struct bio *bio_alloc_bioset(struct block_device *bdev, unsigned short nr_vecs,
 	if (WARN_ON_ONCE(!mempool_initialized(&bs->bvec_pool) && nr_vecs > 0))
 		return NULL;
 
-	gfp = try_alloc_gfp(gfp);
+	if (saved_gfp & __GFP_DIRECT_RECLAIM)
+		gfp = try_alloc_gfp(gfp);
 	if (bs->cache && nr_vecs <= BIO_INLINE_VECS) {
 		/*
 		 * Set REQ_ALLOC_CACHE even if no cached bio is available to