[PARISC] fix null ptr deref in unwind.c

[sfrench/cifs-2.6.git] / block / ll_rw_blk.c

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 17e18897342841887ec25b45585cfe49478bf77a..6b5173ac81313d8adb5c1d7b521559f565bb209b 100644 (file)
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -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.