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authorNeilBrown <neilb@suse.com>2017-06-18 14:38:58 +1000
committerJens Axboe <axboe@kernel.dk>2017-06-18 12:40:59 -0600
commita8821f3f32bea173c7f9546b3b025898f0e09f58 (patch)
treed911354d3c07a5663256d5684d87f8d27435bdb6 /block/bounce.c
parent93b27e72904a9869e648c870bf0d04b124fda1c7 (diff)
block: Improvements to bounce-buffer handling
Since commit 23688bf4f830 ("block: ensure to split after potentially bouncing a bio") blk_queue_bounce() is called *before* blk_queue_split(). This means that: 1/ the comments blk_queue_split() about bounce buffers are irrelevant, and 2/ a very large bio (more than BIO_MAX_PAGES) will no longer be split before it arrives at blk_queue_bounce(), leading to the possibility that bio_clone_bioset() will fail and a NULL will be dereferenced. Separately, blk_queue_bounce() shouldn't use fs_bio_set as the bio being copied could be from the same set, and this could lead to a deadlock. So: - allocate 2 private biosets for blk_queue_bounce, one for splitting enormous bios and one for cloning bios. - add code to split a bio that exceeds BIO_MAX_PAGES. - Fix up the comments in blk_queue_split() Credit-to: Ming Lei <tom.leiming@gmail.com> (suggested using single bio_for_each_segment loop) Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bounce.c')
-rw-r--r--block/bounce.c32
1 files changed, 26 insertions, 6 deletions
diff --git a/block/bounce.c b/block/bounce.c
index e4703181d97f..17d77613c471 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -26,6 +26,7 @@
#define POOL_SIZE 64
#define ISA_POOL_SIZE 16
+struct bio_set *bounce_bio_set, *bounce_bio_split;
static mempool_t *page_pool, *isa_page_pool;
#if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
@@ -40,6 +41,14 @@ static __init int init_emergency_pool(void)
BUG_ON(!page_pool);
pr_info("pool size: %d pages\n", POOL_SIZE);
+ bounce_bio_set = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
+ BUG_ON(!bounce_bio_set);
+ if (bioset_integrity_create(bounce_bio_set, BIO_POOL_SIZE))
+ BUG_ON(1);
+
+ bounce_bio_split = bioset_create(BIO_POOL_SIZE, 0, 0);
+ BUG_ON(!bounce_bio_split);
+
return 0;
}
@@ -186,15 +195,26 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
int rw = bio_data_dir(*bio_orig);
struct bio_vec *to, from;
struct bvec_iter iter;
- unsigned i;
+ unsigned i = 0;
+ bool bounce = false;
+ int sectors = 0;
- bio_for_each_segment(from, *bio_orig, iter)
+ bio_for_each_segment(from, *bio_orig, iter) {
+ if (i++ < BIO_MAX_PAGES)
+ sectors += from.bv_len >> 9;
if (page_to_pfn(from.bv_page) > queue_bounce_pfn(q))
- goto bounce;
+ bounce = true;
+ }
+ if (!bounce)
+ return;
- return;
-bounce:
- bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
+ if (sectors < bio_sectors(*bio_orig)) {
+ bio = bio_split(*bio_orig, sectors, GFP_NOIO, bounce_bio_split);
+ bio_chain(bio, *bio_orig);
+ generic_make_request(*bio_orig);
+ *bio_orig = bio;
+ }
+ bio = bio_clone_bioset(*bio_orig, GFP_NOIO, bounce_bio_set);
bio_for_each_segment_all(to, bio, i) {
struct page *page = to->bv_page;