alinux: block: replace reserved field with extended bio_flags

task #28327019

Commit bc0cc360 ("alinux: blk-throttle: fix tg NULL pointer
dereference") add an self-defined bio flags to fix an issue of
use-after-free. But it is limited to 13 entry and has used up,
hence it will fails to sync related patch.

The patch replace reserved field with extended bio_flags to allow
us to define more bio flags.
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
Signed-off-by: Nzhongjiang-ali <zhongjiang-ali@linux.alibaba.com>

block/blk-throttle.c

@@ -1120,7 +1120,7 @@ static void throtl_bio_end_io(struct bio *bio)
 
 	rcu_read_lock();
 	/* see comments in throtl_bio_stats_start() */
-	if (!bio_flagged(bio, BIO_THROTL_STATED))
+	if (!bio_ext_flagged(bio, BIO_THROTL_STATED))
 		goto out;
 
 	tg = (struct throtl_grp *)bio->bi_tg_private;
@@ -1131,7 +1131,7 @@ static void throtl_bio_end_io(struct bio *bio)
 				       bio_io_start_time_ns(bio),
 				       bio_op(bio));
 	blkg_put(tg_to_blkg(tg));
-	bio_clear_flag(bio, BIO_THROTL_STATED);
+	bio_clear_ext_flag(bio, BIO_THROTL_STATED);
 out:
 	rcu_read_unlock();
 }
@@ -1147,9 +1147,9 @@ static inline void throtl_bio_stats_start(struct bio *bio, struct throtl_grp *tg
 	 * BIO_THROTL_STATED to do only once statistics.
 	 */
 	if ((op == REQ_OP_READ || op == REQ_OP_WRITE) &&
-	    !bio_flagged(bio, BIO_THROTL_STATED)) {
+	    !bio_ext_flagged(bio, BIO_THROTL_STATED)) {
 		blkg_get(tg_to_blkg(tg));
-		bio_set_flag(bio, BIO_THROTL_STATED);
+		bio_set_ext_flag(bio, BIO_THROTL_STATED);
 		bio->bi_tg_end_io = throtl_bio_end_io;
 		bio->bi_tg_private = tg;
 		bio_set_start_time_ns(bio);

include/linux/bio.h

@@ -291,6 +291,21 @@ static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
 	bio->bi_flags &= ~(1U << bit);
 }
 
+static inline bool bio_ext_flagged(struct bio *bio, unsigned int bit)
+{
+	return (bio->bi_ext_flags & (1U << bit)) != 0;
+}
+
+static inline void bio_set_ext_flag(struct bio *bio, unsigned int bit)
+{
+	bio->bi_ext_flags |= (1U << bit);
+}
+
+static inline void bio_clear_ext_flag(struct bio *bio, unsigned int bit)
+{
+	bio->bi_ext_flags &= ~(1U << bit);
+}
+
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
 	*bv = bio_iovec(bio);

include/linux/blk_types.h

@@ -214,8 +214,9 @@ struct bio {
 
 	struct bio_set		*bi_pool;
 
+	unsigned long		bi_ext_flags;	/* extend the bi_flags */
+
 	ALI_HOTFIX_RESERVE(1)
-	ALI_HOTFIX_RESERVE(2)
 
 	/*
 	 * We can inline a number of vecs at the end of the bio, to avoid
@@ -244,7 +245,11 @@ struct bio {
 #define BIO_TRACE_COMPLETION 10	/* bio_endio() should trace the final completion
 				 * of this bio. */
 #define BIO_QUEUE_ENTERED 11	/* can use blk_queue_enter_live() */
-#define BIO_THROTL_STATED 12	/* bio already stated */
+
+/*
+ * Extend bio flags should be added in here
+ */
+#define BIO_THROTL_STATED 0	/* bio already stated */
 
 /* See BVEC_POOL_OFFSET below before adding new flags */