Merge branch 'for-3.6/core' of git://git.kernel.dk/linux-block

Pull core block IO bits from Jens Axboe:
 "The most complicated part if this is the request allocation rework by
  Tejun, which has been queued up for a long time and has been in
  for-next ditto as well.

  There are a few commits from yesterday and today, mostly trivial and
  obvious fixes.  So I'm pretty confident that it is sound.  It's also
  smaller than usual."

* 'for-3.6/core' of git://git.kernel.dk/linux-block:
  block: remove dead func declaration
  block: add partition resize function to blkpg ioctl
  block: uninitialized ioc->nr_tasks triggers WARN_ON
  block: do not artificially constrain max_sectors for stacking drivers
  blkcg: implement per-blkg request allocation
  block: prepare for multiple request_lists
  block: add q->nr_rqs[] and move q->rq.elvpriv to q->nr_rqs_elvpriv
  blkcg: inline bio_blkcg() and friends
  block: allocate io_context upfront
  block: refactor get_request[_wait]()
  block: drop custom queue draining used by scsi_transport_{iscsi|fc}
  mempool: add @gfp_mask to mempool_create_node()
  blkcg: make root blkcg allocation use %GFP_KERNEL
  blkcg: __blkg_lookup_create() doesn't need radix preload

1 files changed, 57 insertions, 0 deletions

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index ae0aaa9d42fa..4f440b3e89fe 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -97,7 +97,13 @@ struct partition_meta_info {
 
 struct hd_struct {
 	sector_t start_sect;
+	/*
+	 * nr_sects is protected by sequence counter. One might extend a
+	 * partition while IO is happening to it and update of nr_sects
+	 * can be non-atomic on 32bit machines with 64bit sector_t.
+	 */
 	sector_t nr_sects;
+	seqcount_t nr_sects_seq;
 	sector_t alignment_offset;
 	unsigned int discard_alignment;
 	struct device __dev;
@@ -647,6 +653,57 @@ static inline void hd_struct_put(struct hd_struct *part)
 		__delete_partition(part);
 }
 
+/*
+ * Any access of part->nr_sects which is not protected by partition
+ * bd_mutex or gendisk bdev bd_mutex, should be done using this
+ * accessor function.
+ *
+ * Code written along the lines of i_size_read() and i_size_write().
+ * CONFIG_PREEMPT case optimizes the case of UP kernel with preemption
+ * on.
+ */
+static inline sector_t part_nr_sects_read(struct hd_struct *part)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_SMP)
+	sector_t nr_sects;
+	unsigned seq;
+	do {
+		seq = read_seqcount_begin(&part->nr_sects_seq);
+		nr_sects = part->nr_sects;
+	} while (read_seqcount_retry(&part->nr_sects_seq, seq));
+	return nr_sects;
+#elif BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_PREEMPT)
+	sector_t nr_sects;
+
+	preempt_disable();
+	nr_sects = part->nr_sects;
+	preempt_enable();
+	return nr_sects;
+#else
+	return part->nr_sects;
+#endif
+}
+
+/*
+ * Should be called with mutex lock held (typically bd_mutex) of partition
+ * to provide mutual exlusion among writers otherwise seqcount might be
+ * left in wrong state leaving the readers spinning infinitely.
+ */
+static inline void part_nr_sects_write(struct hd_struct *part, sector_t size)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_SMP)
+	write_seqcount_begin(&part->nr_sects_seq);
+	part->nr_sects = size;
+	write_seqcount_end(&part->nr_sects_seq);
+#elif BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_PREEMPT)
+	preempt_disable();
+	part->nr_sects = size;
+	preempt_enable();
+#else
+	part->nr_sects = size;
+#endif
+}
+
 #else /* CONFIG_BLOCK */
 
 static inline void printk_all_partitions(void) { }