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Btrfs: Cache free inode numbers in memory

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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>
This commit is contained in:
Li Zefan
2011-04-20 10:06:11 +08:00
parent 34d52cb6c5
commit 581bb05094
10 changed files with 500 additions and 53 deletions
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4
fs/btrfs/ioctl.c
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@@ -50,6 +50,7 @@
#include "print-tree.h"
#include "volumes.h"
#include "locking.h"
#include "inode-map.h"
/* Mask out flags that are inappropriate for the given type of inode. */
static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
@@ -323,8 +324,7 @@ static noinline int create_subvol(struct btrfs_root *root,
u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
u64 index = 0;
ret = btrfs_find_free_objectid(NULL, root->fs_info->tree_root,
0, &objectid);
ret = btrfs_find_free_objectid(root->fs_info->tree_root, &objectid);
if (ret) {
dput(parent);
return ret;