Merge tag 'md/3.16' of git://neil.brown.name/md

Pull md updates from Neil Brown:
 "Assorted md fixes for 3.16

  Mostly performance improvements with a few corner-case bug fixes"

* tag 'md/3.16' of git://neil.brown.name/md:
  raid5: speedup sync_request processing
  md/raid5: deadlock between retry_aligned_read with barrier io
  raid5: add an option to avoid copy data from bio to stripe cache
  md/bitmap: remove confusing code from filemap_get_page.
  raid5: avoid release list until last reference of the stripe
  md: md_clear_badblocks should return an error code on failure.
  md/raid56: Don't perform reads to support writes until stripe is ready.
  md: refuse to change shape of array if it is active but read-only

drivers/md/bitmap.c

@@ -669,17 +669,13 @@ static inline unsigned long file_page_offset(struct bitmap_storage *store,
 /*
  * return a pointer to the page in the filemap that contains the given bit
  *
- * this lookup is complicated by the fact that the bitmap sb might be exactly
- * 1 page (e.g., x86) or less than 1 page -- so the bitmap might start on page
- * 0 or page 1
  */
 static inline struct page *filemap_get_page(struct bitmap_storage *store,
 					    unsigned long chunk)
 {
 	if (file_page_index(store, chunk) >= store->file_pages)
 		return NULL;
-	return store->filemap[file_page_index(store, chunk)
-			      - file_page_index(store, 0)];
+	return store->filemap[file_page_index(store, chunk)];
 }
 
 static int bitmap_storage_alloc(struct bitmap_storage *store,

drivers/md/md.c

@@ -3448,6 +3448,8 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->level = LEVEL_NONE;
 		return rv;
 	}
+	if (mddev->ro)
+		return  -EROFS;
 
 	/* request to change the personality.  Need to ensure:
 	 *  - array is not engaged in resync/recovery/reshape
@@ -3634,6 +3636,8 @@ layout_store(struct mddev *mddev, const char *buf, size_t len)
 		int err;
 		if (mddev->pers->check_reshape == NULL)
 			return -EBUSY;
+		if (mddev->ro)
+			return -EROFS;
 		mddev->new_layout = n;
 		err = mddev->pers->check_reshape(mddev);
 		if (err) {
@@ -3723,6 +3727,8 @@ chunk_size_store(struct mddev *mddev, const char *buf, size_t len)
 		int err;
 		if (mddev->pers->check_reshape == NULL)
 			return -EBUSY;
+		if (mddev->ro)
+			return -EROFS;
 		mddev->new_chunk_sectors = n >> 9;
 		err = mddev->pers->check_reshape(mddev);
 		if (err) {
@@ -6135,6 +6141,8 @@ static int update_size(struct mddev *mddev, sector_t num_sectors)
 	 */
 	if (mddev->sync_thread)
 		return -EBUSY;
+	if (mddev->ro)
+		return -EROFS;
 
 	rdev_for_each(rdev, mddev) {
 		sector_t avail = rdev->sectors;
@@ -6157,6 +6165,8 @@ static int update_raid_disks(struct mddev *mddev, int raid_disks)
 	/* change the number of raid disks */
 	if (mddev->pers->check_reshape == NULL)
 		return -EINVAL;
+	if (mddev->ro)
+		return -EROFS;
 	if (raid_disks <= 0 ||
 	    (mddev->max_disks && raid_disks >= mddev->max_disks))
 		return -EINVAL;
@@ -8333,7 +8343,7 @@ static int md_clear_badblocks(struct badblocks *bb, sector_t s, int sectors)
 			if (a < s) {
 				/* we need to split this range */
 				if (bb->count >= MD_MAX_BADBLOCKS) {
-					rv = 0;
+					rv = -ENOSPC;
 					goto out;
 				}
 				memmove(p+lo+1, p+lo, (bb->count - lo) * 8);

drivers/md/raid5.h

@@ -232,7 +232,7 @@ struct stripe_head {
 		 */
 		struct bio	req, rreq;
 		struct bio_vec	vec, rvec;
-		struct page	*page;
+		struct page	*page, *orig_page;
 		struct bio	*toread, *read, *towrite, *written;
 		sector_t	sector;			/* sector of this page */
 		unsigned long	flags;
@@ -299,6 +299,7 @@ enum r5dev_flags {
 			 * data in, and now is a good time to write it out.
 			 */
 	R5_Discard,	/* Discard the stripe */
+	R5_SkipCopy,	/* Don't copy data from bio to stripe cache */
 };
 
 /*
@@ -436,6 +437,7 @@ struct r5conf {
 	atomic_t		pending_full_writes; /* full write backlog */
 	int			bypass_count; /* bypassed prereads */
 	int			bypass_threshold; /* preread nice */
+	int			skip_copy; /* Don't copy data from bio to stripe cache */
 	struct list_head	*last_hold; /* detect hold_list promotions */
 
 	atomic_t		reshape_stripes; /* stripes with pending writes for reshape */