[PATCH 1/2] fs: Change iterate_bdevs() to iterate over all_bdevs list instead of blockdev_superblock

[Jan Kara <jack@suse.cz>]

It is better to iterate over all_bdevs list in iterate_bdevs() because
inode list of blockdev_super contains also inodes which are not describing
any block device (e.g. root of bdev filesystem).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/block_dev.c |   45 +++++++++++++++++++++++++--------------------
 1 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 38e721b..220391c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1716,36 +1716,41 @@ EXPORT_SYMBOL(__invalidate_device);
 
 void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
 {
-	struct inode *inode, *old_inode = NULL;
-
-	spin_lock(&inode_sb_list_lock);
-	list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
-		struct address_space *mapping = inode->i_mapping;
+	struct block_device *bdev, *old_bdev = NULL;
+	struct inode *inode;
 
+	spin_lock(&bdev_lock);
+	list_for_each_entry(bdev, &all_bdevs, bd_list) {
+		inode = bdev->bd_inode;
 		spin_lock(&inode->i_lock);
+		/*
+		 * With i_lock we can safely check bdev isn't freeing and
+		 * grab our reference.
+		 */
 		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
-		    mapping->nrpages == 0) {
+		    inode->i_mapping->nrpages == 0) {
 			spin_unlock(&inode->i_lock);
 			continue;
 		}
-		__iget(inode);
+		bdgrab(bdev);
 		spin_unlock(&inode->i_lock);
-		spin_unlock(&inode_sb_list_lock);
+		spin_unlock(&bdev_lock);
 		/*
-		 * We hold a reference to 'inode' so it couldn't have been
-		 * removed from s_inodes list while we dropped the
-		 * inode_sb_list_lock.  We cannot iput the inode now as we can
-		 * be holding the last reference and we cannot iput it under
-		 * inode_sb_list_lock. So we keep the reference and iput it
-		 * later.
+		 * We hold a reference to 'bdev' so it couldn't have been
+		 * removed from the list while we dropped the bdev_lock.  We
+		 * cannot put the reference now as we can be holding the last
+		 * reference and we cannot put it under bdev_lock. So we keep
+		 * the reference and put it later.
 		 */
-		iput(old_inode);
-		old_inode = inode;
+		if (old_bdev)
+			bdput(old_bdev);
+		old_bdev = bdev;
 
-		func(I_BDEV(inode), arg);
+		func(bdev, arg);
 
-		spin_lock(&inode_sb_list_lock);
+		spin_lock(&bdev_lock);
 	}
-	spin_unlock(&inode_sb_list_lock);
-	iput(old_inode);
+	spin_unlock(&bdev_lock);
+	if (old_bdev)
+		bdput(old_bdev);
 }
-- 
1.7.1