nilfs2: implement calculation of free inodes count

Currently, NILFS2 returns 0 as free inodes count (f_ffree) and current
used inodes count as total file nodes in file system (f_files):

df -i
Filesystem      Inodes  IUsed   IFree IUse% Mounted on
/dev/loop0           2      2       0  100% /mnt/nilfs2

This patch implements real calculation of free inodes count.  First of
all, it is calculated total file nodes in file system as
(desc_blocks_count * groups_per_desc_block * entries_per_group).  Then, it
is calculated free inodes count as difference the total file nodes and
used inodes count.  As a result, we have such output for NILFS2:

df -i
Filesystem       Inodes   IUsed    IFree IUse% Mounted on
/dev/loop0      4194304 2114701  2079603   51% /mnt/nilfs2

Reported-by: Clemens Eisserer <linuxhippy@gmail.com>
Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Joern Engel <joern@logfs.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 112 insertions, 2 deletions

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index eed4d7b26249..741fd02e0444 100644
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -398,6 +398,69 @@ nilfs_palloc_rest_groups_in_desc_block(const struct inode *inode,
 }
 
 /**
+ * nilfs_palloc_count_desc_blocks - count descriptor blocks number
+ * @inode: inode of metadata file using this allocator
+ * @desc_blocks: descriptor blocks number [out]
+ */
+static int nilfs_palloc_count_desc_blocks(struct inode *inode,
+                                            unsigned long *desc_blocks)
+{
+        unsigned long blknum;
+        int ret;
+
+        ret = nilfs_bmap_last_key(NILFS_I(inode)->i_bmap, &blknum);
+        if (likely(!ret))
+                *desc_blocks = DIV_ROUND_UP(
+                        blknum, NILFS_MDT(inode)->mi_blocks_per_desc_block);
+        return ret;
+}
+
+/**
+ * nilfs_palloc_mdt_file_can_grow - check potential opportunity for
+ *                                      MDT file growing
+ * @inode: inode of metadata file using this allocator
+ * @desc_blocks: known current descriptor blocks count
+ */
+static inline bool nilfs_palloc_mdt_file_can_grow(struct inode *inode,
+                                                    unsigned long desc_blocks)
+{
+        return (nilfs_palloc_groups_per_desc_block(inode) * desc_blocks) <
+                        nilfs_palloc_groups_count(inode);
+}
+
+/**
+ * nilfs_palloc_count_max_entries - count max number of entries that can be
+ *                                      described by descriptor blocks count
+ * @inode: inode of metadata file using this allocator
+ * @nused: current number of used entries
+ * @nmaxp: max number of entries [out]
+ */
+int nilfs_palloc_count_max_entries(struct inode *inode, u64 nused, u64 *nmaxp)
+{
+        unsigned long desc_blocks = 0;
+        u64 entries_per_desc_block, nmax;
+        int err;
+
+        err = nilfs_palloc_count_desc_blocks(inode, &desc_blocks);
+        if (unlikely(err))
+                return err;
+
+        entries_per_desc_block = (u64)nilfs_palloc_entries_per_group(inode) *
+                                nilfs_palloc_groups_per_desc_block(inode);
+        nmax = entries_per_desc_block * desc_blocks;
+
+        if (nused == nmax &&
+                        nilfs_palloc_mdt_file_can_grow(inode, desc_blocks))
+                nmax += entries_per_desc_block;
+
+        if (nused > nmax)
+                return -ERANGE;
+
+        *nmaxp = nmax;
+        return 0;
+}
+
+/**
  * nilfs_palloc_prepare_alloc_entry - prepare to allocate a persistent object
  * @inode: inode of metadata file using this allocator
  * @req: nilfs_palloc_req structure exchanged for the allocation
diff --git a/fs/nilfs2/alloc.h b/fs/nilfs2/alloc.h
index fb7238100548..4bd6451b5703 100644
--- a/fs/nilfs2/alloc.h
+++ b/fs/nilfs2/alloc.h
@@ -48,6 +48,8 @@ int nilfs_palloc_get_entry_block(struct inode *, __u64, int,
 void *nilfs_palloc_block_get_entry(const struct inode *, __u64,
                                    const struct buffer_head *, void *);
 
+int nilfs_palloc_count_max_entries(struct inode *, u64, u64 *);
+
 /**
  * nilfs_palloc_req - persistent allocator request and reply
  * @pr_entry_nr: entry number (vblocknr or inode number)
diff --git a/fs/nilfs2/ifile.c b/fs/nilfs2/ifile.c
index d8e65bde083c..d788a5928351 100644
--- a/fs/nilfs2/ifile.c
+++ b/fs/nilfs2/ifile.c
@@ -160,6 +160,28 @@ int nilfs_ifile_get_inode_block(struct inode *ifile, ino_t ino,
 }
 
 /**
+ * nilfs_ifile_count_free_inodes - calculate free inodes count
+ * @ifile: ifile inode
+ * @nmaxinodes: current maximum of available inodes count [out]
+ * @nfreeinodes: free inodes count [out]
+ */
+int nilfs_ifile_count_free_inodes(struct inode *ifile,
+                                    u64 *nmaxinodes, u64 *nfreeinodes)
+{
+        u64 nused;
+        int err;
+
+        *nmaxinodes = 0;
+        *nfreeinodes = 0;
+
+        nused = atomic_read(&NILFS_I(ifile)->i_root->inodes_count);
+        err = nilfs_palloc_count_max_entries(ifile, nused, nmaxinodes);
+        if (likely(!err))
+                *nfreeinodes = *nmaxinodes - nused;
+        return err;
+}
+
+/**
  * nilfs_ifile_read - read or get ifile inode
  * @sb: super block instance
  * @root: root object
diff --git a/fs/nilfs2/ifile.h b/fs/nilfs2/ifile.h
index 59b6f2b51df6..679674d13372 100644
--- a/fs/nilfs2/ifile.h
+++ b/fs/nilfs2/ifile.h
@@ -49,6 +49,8 @@ int nilfs_ifile_create_inode(struct inode *, ino_t *, struct buffer_head **);
 int nilfs_ifile_delete_inode(struct inode *, ino_t);
 int nilfs_ifile_get_inode_block(struct inode *, ino_t, struct buffer_head **);
 
+int nilfs_ifile_count_free_inodes(struct inode *, u64 *, u64 *);
+
 int nilfs_ifile_read(struct super_block *sb, struct nilfs_root *root,
                      size_t inode_size, struct nilfs_inode *raw_inode,
                      struct inode **inodep);
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index c7d1f9f18b09..7d257e78fbad 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -609,6 +609,7 @@ static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
         unsigned long overhead;
         unsigned long nrsvblocks;
         sector_t nfreeblocks;
+        u64 nmaxinodes, nfreeinodes;
         int err;
 
         /*
@@ -633,14 +634,34 @@ static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
         if (unlikely(err))
                 return err;
 
+        err = nilfs_ifile_count_free_inodes(root->ifile,
+                                            &nmaxinodes, &nfreeinodes);
+        if (unlikely(err)) {
+                printk(KERN_WARNING
+                        "NILFS warning: fail to count free inodes: err %d.\n",
+                        err);
+                if (err == -ERANGE) {
+                        /*
+                         * If nilfs_palloc_count_max_entries() returns
+                         * -ERANGE error code then we simply treat
+                         * curent inodes count as maximum possible and
+                         * zero as free inodes value.
+                         */
+                        nmaxinodes = atomic_read(&root->inodes_count);
+                        nfreeinodes = 0;
+                        err = 0;
+                } else
+                        return err;
+        }
+
         buf->f_type = NILFS_SUPER_MAGIC;
         buf->f_bsize = sb->s_blocksize;
         buf->f_blocks = blocks - overhead;
         buf->f_bfree = nfreeblocks;
         buf->f_bavail = (buf->f_bfree >= nrsvblocks) ?
                 (buf->f_bfree - nrsvblocks) : 0;
-        buf->f_files = atomic_read(&root->inodes_count);
-        buf->f_ffree = 0; /* nilfs_count_free_inodes(sb); */
+        buf->f_files = nmaxinodes;
+        buf->f_ffree = nfreeinodes;
         buf->f_namelen = NILFS_NAME_LEN;
         buf->f_fsid.val[0] = (u32)id;
         buf->f_fsid.val[1] = (u32)(id >> 32);