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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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16
fs/btrfs/free-space-cache.h
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@@ -64,15 +64,25 @@ int btrfs_write_out_cache(struct btrfs_root *root,
struct btrfs_trans_handle *trans,
struct btrfs_block_group_cache *block_group,
struct btrfs_path *path);
void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group);
int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
u64 bytenr, u64 size);
int __btrfs_add_free_space(struct btrfs_free_space_ctl *ctl,
u64 bytenr, u64 size);
static inline int
btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
u64 bytenr, u64 size)
{
return __btrfs_add_free_space(block_group->free_space_ctl,
bytenr, size);
}
int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
u64 bytenr, u64 size);
void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl);
void btrfs_remove_free_space_cache(struct btrfs_block_group_cache
*block_group);
*block_group);
u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
u64 offset, u64 bytes, u64 empty_size);
u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root);
void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
u64 bytes);
int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,