Btrfs: Cache free inode numbers in memory

Currently btrfs stores the highest objectid of the fs tree, and it always
returns (highest+1) inode number when we create a file, so inode numbers
won't be reclaimed when we delete files, so we'll run out of inode numbers
as we keep create/delete files in 32bits machines.

This fixes it, and it works similarly to how we cache free space in block
cgroups.

We start a kernel thread to read the file tree. By scanning inode items,
we know which chunks of inode numbers are free, and we cache them in
an rb-tree.

Because we are searching the commit root, we have to carefully handle the
cross-transaction case.

The rb-tree is a hybrid extent+bitmap tree, so if we have too many small
chunks of inode numbers, we'll use bitmaps. Initially we allow 16K ram
of extents, and a bitmap will be used if we exceed this threshold. The
extents threshold is adjusted in runtime.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 27 insertions, 15 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a4157cfdd533..77dd0a776c83 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -51,6 +51,7 @@
 #include "compression.h"
 #include "locking.h"
 #include "free-space-cache.h"
+#include "inode-map.h"
 
 struct btrfs_iget_args {
         u64 ino;
@@ -3809,6 +3810,10 @@ void btrfs_evict_inode(struct inode *inode)
                 BUG_ON(ret);
         }
 
+        if (!(root == root->fs_info->tree_root ||
+              root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID))
+                btrfs_return_ino(root, inode->i_ino);
+
         nr = trans->blocks_used;
         btrfs_end_transaction(trans, root);
         btrfs_btree_balance_dirty(root, nr);
@@ -4538,6 +4543,12 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                 return ERR_PTR(-ENOMEM);
         }
 
+        /*
+         * we have to initialize this early, so we can reclaim the inode
+         * number if we fail afterwards in this function.
+         */
+        inode->i_ino = objectid;
+
         if (dir) {
                 trace_btrfs_inode_request(dir);
 
@@ -4583,7 +4594,6 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                 goto fail;
 
         inode_init_owner(inode, dir, mode);
-        inode->i_ino = objectid;
         inode_set_bytes(inode, 0);
         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
         inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
@@ -4712,10 +4722,6 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
         if (!new_valid_dev(rdev))
                 return -EINVAL;
 
-        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
-        if (err)
-                return err;
-
         /*
          * 2 for inode item and ref
          * 2 for dir items
@@ -4727,6 +4733,10 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
 
         btrfs_set_trans_block_group(trans, dir);
 
+        err = btrfs_find_free_ino(root, &objectid);
+        if (err)
+                goto out_unlock;
+
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len, dir->i_ino, objectid,
                                 BTRFS_I(dir)->block_group, mode, &index);
@@ -4774,9 +4784,6 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
         u64 objectid;
         u64 index = 0;
 
-        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
-        if (err)
-                return err;
         /*
          * 2 for inode item and ref
          * 2 for dir items
@@ -4788,6 +4795,10 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
 
         btrfs_set_trans_block_group(trans, dir);
 
+        err = btrfs_find_free_ino(root, &objectid);
+        if (err)
+                goto out_unlock;
+
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len, dir->i_ino, objectid,
                                 BTRFS_I(dir)->block_group, mode, &index);
@@ -4902,10 +4913,6 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         u64 index = 0;
         unsigned long nr = 1;
 
-        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
-        if (err)
-                return err;
-
         /*
          * 2 items for inode and ref
          * 2 items for dir items
@@ -4916,6 +4923,10 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
                 return PTR_ERR(trans);
         btrfs_set_trans_block_group(trans, dir);
 
+        err = btrfs_find_free_ino(root, &objectid);
+        if (err)
+                goto out_fail;
+
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len, dir->i_ino, objectid,
                                 BTRFS_I(dir)->block_group, S_IFDIR | mode,
@@ -7257,9 +7268,6 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
         if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                 return -ENAMETOOLONG;
 
-        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
-        if (err)
-                return err;
         /*
          * 2 items for inode item and ref
          * 2 items for dir items
@@ -7271,6 +7279,10 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 
         btrfs_set_trans_block_group(trans, dir);
 
+        err = btrfs_find_free_ino(root, &objectid);
+        if (err)
+                goto out_unlock;
+
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len, dir->i_ino, objectid,
                                 BTRFS_I(dir)->block_group, S_IFLNK|S_IRWXUGO,