f2fs: introduce private bioset

In low memory scenario, we can allocate multiple bios without
submitting any of them.

- f2fs_write_checkpoint()
 - block_operations()
  - f2fs_sync_node_pages()
   step 1) flush cold nodes, allocate new bio from mempool
   - bio_alloc()
    - mempool_alloc()
   step 2) flush hot nodes, allocate a bio from mempool
   - bio_alloc()
    - mempool_alloc()
   step 3) flush warm nodes, be stuck in below call path
   - bio_alloc()
    - mempool_alloc()
     - loop to wait mempool element release, as we only
       reserved memory for two bio allocation, however above
       allocated two bios may never be submitted.

So we need avoid using default bioset, in this patch we introduce a
private bioset, in where we enlarg mempool element count to total
number of log header, so that we can make sure we have enough
backuped memory pool in scenario of allocating/holding multiple
bios.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 3b29451..f89aeaa 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -31,6 +31,47 @@
 static struct kmem_cache *bio_post_read_ctx_cache;
 static struct kmem_cache *bio_entry_slab;
 static mempool_t *bio_post_read_ctx_pool;
+static struct bio_set f2fs_bioset;
+
+#define	F2FS_BIO_POOL_SIZE	NR_CURSEG_TYPE
+
+int __init f2fs_init_bioset(void)
+{
+	if (bioset_init(&f2fs_bioset, F2FS_BIO_POOL_SIZE,
+					0, BIOSET_NEED_BVECS))
+		return -ENOMEM;
+	return 0;
+}
+
+void f2fs_destroy_bioset(void)
+{
+	bioset_exit(&f2fs_bioset);
+}
+
+static inline struct bio *__f2fs_bio_alloc(gfp_t gfp_mask,
+						unsigned int nr_iovecs)
+{
+	return bio_alloc_bioset(gfp_mask, nr_iovecs, &f2fs_bioset);
+}
+
+struct bio *f2fs_bio_alloc(struct f2fs_sb_info *sbi, int npages, bool no_fail)
+{
+	struct bio *bio;
+
+	if (no_fail) {
+		/* No failure on bio allocation */
+		bio = __f2fs_bio_alloc(GFP_NOIO, npages);
+		if (!bio)
+			bio = __f2fs_bio_alloc(GFP_NOIO | __GFP_NOFAIL, npages);
+		return bio;
+	}
+	if (time_to_inject(sbi, FAULT_ALLOC_BIO)) {
+		f2fs_show_injection_info(sbi, FAULT_ALLOC_BIO);
+		return NULL;
+	}
+
+	return __f2fs_bio_alloc(GFP_KERNEL, npages);
+}
 
 static bool __is_cp_guaranteed(struct page *page)
 {
@@ -3317,7 +3358,7 @@ int __init f2fs_init_bio_entry_cache(void)
 	return 0;
 }
 
-void __exit f2fs_destroy_bio_entry_cache(void)
+void f2fs_destroy_bio_entry_cache(void)
 {
 	kmem_cache_destroy(bio_entry_slab);
 }