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authorShaohua Li <shli@fb.com>2017-07-12 11:49:47 -0700
committerJens Axboe <axboe@kernel.dk>2017-07-29 09:00:03 -0600
commit4a3ef68acacf31570066e69593de5cc49cc91638 (patch)
tree5cdcf8c5c9208f323152af655e1da6be0093316a /fs/kernfs/dir.c
parent7d35079f8277b653d6a3075eea9edd4dbf7c2b29 (diff)
downloadlinux-4a3ef68acacf31570066e69593de5cc49cc91638.tar.bz2
kernfs: implement i_generation
Set i_generation for kernfs inode. This is required to implement exportfs operations. The generation is 32-bit, so it's possible the generation wraps up and we find stale files. To reduce the posssibility, we don't reuse inode numer immediately. When the inode number allocation wraps, we increase generation number. In this way generation/inode number consist of a 64-bit number which is unlikely duplicated. This does make the idr tree more sparse and waste some memory. Since idr manages 32-bit keys, idr uses a 6-level radix tree, each level covers 6 bits of the key. In a 100k inode kernfs, the worst case will have around 300k radix tree node. Each node is 576bytes, so the tree will use about ~150M memory. Sounds not too bad, if this really is a problem, we should find better data structure. Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/kernfs/dir.c')
-rw-r--r--fs/kernfs/dir.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8ad7a17895fe..33f711f6b86e 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -623,6 +623,8 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
unsigned flags)
{
struct kernfs_node *kn;
+ u32 gen;
+ int cursor;
int ret;
name = kstrdup_const(name, GFP_KERNEL);
@@ -635,12 +637,17 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
idr_preload(GFP_KERNEL);
spin_lock(&kernfs_idr_lock);
- ret = idr_alloc(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
+ cursor = idr_get_cursor(&root->ino_idr);
+ ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
+ if (ret >= 0 && ret < cursor)
+ root->next_generation++;
+ gen = root->next_generation;
spin_unlock(&kernfs_idr_lock);
idr_preload_end();
if (ret < 0)
goto err_out2;
kn->ino = ret;
+ kn->generation = gen;
atomic_set(&kn->count, 1);
atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
@@ -884,6 +891,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
idr_init(&root->ino_idr);
INIT_LIST_HEAD(&root->supers);
+ root->next_generation = 1;
kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
KERNFS_DIR);