From: Howard McLauchlan <hmclauchlan@fb.com>
Date: Tue, 6 Feb 2018 22:05:39 +0000 (-0800)
Subject: block: Add should_fail_bio() for bpf error injection
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=30abb3a67f4b2aa160feeb3c0b771f730cbcca67;p=openwrt%2Fstaging%2Fblogic.git

block: Add should_fail_bio() for bpf error injection

The classic error injection mechanism, should_fail_request() does not
support use cases where more information is required (from the entire
struct bio, for example).

To that end, this patch introduces should_fail_bio(), which calls
should_fail_request() under the hood but provides a convenient
place for kprobes to hook into if they require the entire struct bio.
This patch also replaces some existing calls to should_fail_request()
with should_fail_bio() with no degradation in performance.

Signed-off-by: Howard McLauchlan <hmclauchlan@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/blk-core.c b/block/blk-core.c
index d0d104268f1a..2d1a7bbe0634 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -34,6 +34,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/blk-cgroup.h>
 #include <linux/debugfs.h>
+#include <linux/bpf.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/block.h>
@@ -2083,6 +2084,14 @@ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part)
 	return false;
 }
 
+static noinline int should_fail_bio(struct bio *bio)
+{
+	if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size))
+		return -EIO;
+	return 0;
+}
+ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
+
 /*
  * Remap block n of partition p to block n+start(p) of the disk.
  */
@@ -2174,7 +2183,7 @@ generic_make_request_checks(struct bio *bio)
 	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_rq_based(q))
 		goto not_supported;
 
-	if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size))
+	if (should_fail_bio(bio))
 		goto end_io;
 
 	if (!bio->bi_partno) {