vfs: Create function for iterating over block devices

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 41 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c2bbe1fb1326..1e519195d45b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1710,3 +1710,39 @@ int __invalidate_device(struct block_device *bdev, bool kill_dirty)
         return res;
 }
 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;
+
+                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);
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 48548bdd7722..6a6ca85bee23 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2102,6 +2102,7 @@ extern sector_t blkdev_max_block(struct block_device *bdev);
 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 void kill_bdev(struct block_device *);
 extern struct super_block *freeze_bdev(struct block_device *);
@@ -2123,6 +2124,10 @@ static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 {
         return 0;
 }
+
+static inline void iterate_bdevs(void (*f)(struct block_device *, void *), void *arg)
+{
+}
 #endif
 extern int sync_filesystem(struct super_block *);
 extern const struct file_operations def_blk_fops;