[PATCH v2 2/5] ovl: use a private non-persistent ino pool

[Amir Goldstein <amir73il@xxxxxxxxx>]

There is no reason to deplete the system's global get_next_ino() pool
for overlay non-persistent inode numbers and there is no reason at all
to allocate non-persistent inode numbers for non-directories.

For non-directories, it is much better to leave i_ino the same as
real i_ino, to be consistent with st_ino/d_ino.

Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
 fs/overlayfs/inode.c     | 15 ++++++++++++---
 fs/overlayfs/ovl_entry.h |  2 ++
 fs/overlayfs/super.c     |  1 +
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 13219a5864c4..1d555cb1a5cd 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -561,6 +561,15 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
 #endif
 }
 
+static void ovl_next_ino(struct inode *inode)
+{
+	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
+
+	inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
+	if (unlikely(!inode->i_ino))
+		inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
+}
+
 static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
 {
 	int xinobits = ovl_xino_bits(inode->i_sb);
@@ -572,12 +581,12 @@ static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
 	 * consistent with d_ino and st_ino values. An i_ino value inconsistent
 	 * with d_ino also causes nfsd readdirplus to fail.
 	 */
+	inode->i_ino = ino;
 	if (ovl_same_dev(inode->i_sb)) {
-		inode->i_ino = ino;
 		if (xinobits && fsid && !(ino >> (64 - xinobits)))
 			inode->i_ino |= (unsigned long)fsid << (64 - xinobits);
-	} else {
-		inode->i_ino = get_next_ino();
+	} else if (S_ISDIR(inode->i_mode)) {
+		ovl_next_ino(inode);
 	}
 }
 
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 89015ea822e7..5762d802fe01 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -75,6 +75,8 @@ struct ovl_fs {
 	struct inode *indexdir_trap;
 	/* -1: disabled, 0: same fs, 1..32: number of unused ino bits */
 	int xino_mode;
+	/* For allocation of non-persistent inode numbers */
+	atomic_long_t last_ino;
 };
 
 static inline struct ovl_fs *OVL_FS(struct super_block *sb)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f4c0ad69f9a6..18b710344dd2 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1736,6 +1736,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
 	sb->s_stack_depth = 0;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	atomic_long_set(&ofs->last_ino, 1);
 	/* Assume underlaying fs uses 32bit inodes unless proven otherwise */
 	if (ofs->config.xino != OVL_XINO_OFF) {
 		ofs->xino_mode = BITS_PER_LONG - 32;
-- 
2.17.1