vfs: count unlinked inodes

Add a new counter to the superblock that keeps track of unlinked but
not yet deleted inodes.

Do not WARN_ON if set_nlink is called with zero count, just do a
ratelimited printk.  This happens on xfs and probably other
filesystems after an unclean shutdown when the filesystem reads inodes
which already have zero i_nlink.  Reported by Christoph Hellwig.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 54 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7b8a681b1ef..8ac40921f5a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1483,6 +1483,9 @@ struct super_block {
 
 	struct shrinker s_shrink;	/* per-sb shrinker handle */
 
+	/* Number of inodes with nlink == 0 but still referenced */
+	atomic_long_t s_remove_count;
+
 	/* Being remounted read-only */
 	int s_readonly_remount;
 };
@@ -1768,31 +1771,10 @@ static inline void mark_inode_dirty_sync(struct inode *inode)
 	__mark_inode_dirty(inode, I_DIRTY_SYNC);
 }
 
-/**
- * set_nlink - directly set an inode's link count
- * @inode: inode
- * @nlink: new nlink (should be non-zero)
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink.
- */
-static inline void set_nlink(struct inode *inode, unsigned int nlink)
-{
-	inode->__i_nlink = nlink;
-}
-
-/**
- * inc_nlink - directly increment an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink.  Currently,
- * it is only here for parity with dec_nlink().
- */
-static inline void inc_nlink(struct inode *inode)
-{
-	inode->__i_nlink++;
-}
+extern void inc_nlink(struct inode *inode);
+extern void drop_nlink(struct inode *inode);
+extern void clear_nlink(struct inode *inode);
+extern void set_nlink(struct inode *inode, unsigned int nlink);
 
 static inline void inode_inc_link_count(struct inode *inode)
 {
@@ -1800,35 +1782,6 @@ static inline void inode_inc_link_count(struct inode *inode)
 	mark_inode_dirty(inode);
 }
 
-/**
- * drop_nlink - directly drop an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink.  In cases
- * where we are attempting to track writes to the
- * filesystem, a decrement to zero means an imminent
- * write when the file is truncated and actually unlinked
- * on the filesystem.
- */
-static inline void drop_nlink(struct inode *inode)
-{
-	inode->__i_nlink--;
-}
-
-/**
- * clear_nlink - directly zero an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink.  See
- * drop_nlink() for why we care about i_nlink hitting zero.
- */
-static inline void clear_nlink(struct inode *inode)
-{
-	inode->__i_nlink = 0;
-}
-
 static inline void inode_dec_link_count(struct inode *inode)
 {
 	drop_nlink(inode);