X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=block%2Fll_rw_blk.c;h=ef42bb2b12b6dd89b0edc1734485e66147920759;hb=e8f3f6cad7e423253090887bc4afe7bc844162da;hp=17e18897342841887ec25b45585cfe49478bf77a;hpb=a9deecba19b8f384d97f82c75379da48bccb2588;p=linux-2.6

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 17e1889734..ef42bb2b12 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -340,6 +340,15 @@ unsigned blk_ordered_req_seq(struct request *rq)
 	if (rq == &q->post_flush_rq)
 		return QUEUE_ORDSEQ_POSTFLUSH;
 
+	/*
+	 * !fs requests don't need to follow barrier ordering.  Always
+	 * put them at the front.  This fixes the following deadlock.
+	 *
+	 * http://thread.gmane.org/gmane.linux.kernel/537473
+	 */
+	if (!blk_fs_request(rq))
+		return QUEUE_ORDSEQ_DRAIN;
+
 	if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
 	    (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
 		return QUEUE_ORDSEQ_DRAIN;
@@ -518,8 +527,6 @@ int blk_do_ordered(request_queue_t *q, struct request **rqp)
 static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
 {
 	request_queue_t *q = bio->bi_private;
-	struct bio_vec *bvec;
-	int i;
 
 	/*
 	 * This is dry run, restore bio_sector and size.  We'll finish
@@ -531,13 +538,6 @@ static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
 	if (bio->bi_size)
 		return 1;
 
-	/* Rewind bvec's */
-	bio->bi_idx = 0;
-	bio_for_each_segment(bvec, bio, i) {
-		bvec->bv_len += bvec->bv_offset;
-		bvec->bv_offset = 0;
-	}
-
 	/* Reset bio */
 	set_bit(BIO_UPTODATE, &bio->bi_flags);
 	bio->bi_size = q->bi_size;
@@ -1295,9 +1295,9 @@ static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
 	if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
 		blk_recount_segments(q, nxt);
 	if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
-	    BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
+	    BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))
 		return 0;
-	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+	if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
 		return 0;
 
 	return 1;
@@ -3116,7 +3116,7 @@ static inline int should_fail_request(struct bio *bio)
  * bi_sector for remaps as it sees fit.  So the values of these fields
  * should NOT be depended on after the call to generic_make_request.
  */
-void generic_make_request(struct bio *bio)
+static inline void __generic_make_request(struct bio *bio)
 {
 	request_queue_t *q;
 	sector_t maxsector;
@@ -3215,6 +3215,57 @@ end_io:
 	} while (ret);
 }
 
+/*
+ * We only want one ->make_request_fn to be active at a time,
+ * else stack usage with stacked devices could be a problem.
+ * So use current->bio_{list,tail} to keep a list of requests
+ * submited by a make_request_fn function.
+ * current->bio_tail is also used as a flag to say if
+ * generic_make_request is currently active in this task or not.
+ * If it is NULL, then no make_request is active.  If it is non-NULL,
+ * then a make_request is active, and new requests should be added
+ * at the tail
+ */
+void generic_make_request(struct bio *bio)
+{
+	if (current->bio_tail) {
+		/* make_request is active */
+		*(current->bio_tail) = bio;
+		bio->bi_next = NULL;
+		current->bio_tail = &bio->bi_next;
+		return;
+	}
+	/* following loop may be a bit non-obvious, and so deserves some
+	 * explanation.
+	 * Before entering the loop, bio->bi_next is NULL (as all callers
+	 * ensure that) so we have a list with a single bio.
+	 * We pretend that we have just taken it off a longer list, so
+	 * we assign bio_list to the next (which is NULL) and bio_tail
+	 * to &bio_list, thus initialising the bio_list of new bios to be
+	 * added.  __generic_make_request may indeed add some more bios
+	 * through a recursive call to generic_make_request.  If it
+	 * did, we find a non-NULL value in bio_list and re-enter the loop
+	 * from the top.  In this case we really did just take the bio
+	 * of the top of the list (no pretending) and so fixup bio_list and
+	 * bio_tail or bi_next, and call into __generic_make_request again.
+	 *
+	 * The loop was structured like this to make only one call to
+	 * __generic_make_request (which is important as it is large and
+	 * inlined) and to keep the structure simple.
+	 */
+	BUG_ON(bio->bi_next);
+	do {
+		current->bio_list = bio->bi_next;
+		if (bio->bi_next == NULL)
+			current->bio_tail = &current->bio_list;
+		else
+			bio->bi_next = NULL;
+		__generic_make_request(bio);
+		bio = current->bio_list;
+	} while (bio);
+	current->bio_tail = NULL; /* deactivate */
+}
+
 EXPORT_SYMBOL(generic_make_request);
 
 /**
@@ -3751,7 +3802,6 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
 
 	return ret;
 }
-EXPORT_SYMBOL(current_io_context);
 
 /*
  * If the current task has no IO context then create one and initialise it.