[PATCH 5/8] vfs: Create function for iterating over block devices

[Jan Kara <jack@suse.cz>]

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/block_dev.c     |   36 ++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |    1 +
 2 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b07f1da..4d6631e 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -196,6 +196,42 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 				    nr_segs, blkdev_get_blocks, NULL, NULL, 0);
 }
 
+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;
+
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
+		    mapping->nrpages == 0) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&inode_sb_list_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.
+		 */
+		iput(old_inode);
+		old_inode = inode;
+
+		func(I_BDEV(inode), arg);
+
+		spin_lock(&inode_sb_list_lock);
+	}
+	spin_unlock(&inode_sb_list_lock);
+	iput(old_inode);
+}
+
 int __sync_blockdev(struct block_device *bdev, int wait)
 {
 	if (!bdev)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0c4df26..0404e7c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2089,6 +2089,7 @@ extern void bd_set_size(struct block_device *, loff_t size);
 extern void bd_forget(struct inode *inode);
 extern void bdput(struct block_device *);
 extern void invalidate_bdev(struct block_device *);
+extern void iterate_bdevs(void (*)(struct block_device *, void *), void *);
 extern int sync_blockdev(struct block_device *bdev);
 extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
-- 
1.7.1