On Thu, May 17, 2018 at 11:53 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Thu, May 17, 2018 at 10:10:58AM +0200, Miklos Szeredi wrote:
>>
>> Not the only reason: we don't want inode allocation to fail after
>> successful creation. Solution: add a preallocated inode argument to
>> ovl_get_inode() and deal with allocation failure there.
>
> Here's a patch to split a helper out of iget5_locked() that takes a preallocated
> inode. It makes the whole thing more readable, IMO, regardless of overlayfs's
> needs.
>
That looks good. I'll use that.
One suggestion below.
Thanks,
Amir.
>
> ---
> diff --git a/fs/inode.c b/fs/inode.c
> index 13ceb98c3bd3..bb79e3f96147 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1002,6 +1002,52 @@ void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
> }
> EXPORT_SYMBOL(unlock_two_nondirectories);
>
> +struct inode *iget5_prealloc(struct inode *inode,
> + struct super_block *sb, unsigned long hashval,
Maybe no need to pass in @sb...
> + int (*test)(struct inode *, void *),
> + int (*set)(struct inode *, void *), void *data)
> +{
> + struct hlist_head *head = inode_hashtable + hash(sb, hashval);
> + struct inode *old;
> +
> +again:
> + spin_lock(&inode_hash_lock);
> + old = find_inode(sb, head, test, data);
> + if (unlikely(old)) {
> + /*
> + * Uhhuh, somebody else created the same inode under us.
> + * Use the old inode instead of the preallocated one.
> + */
> + spin_unlock(&inode_hash_lock);
> + wait_on_inode(old);
> + if (unlikely(inode_unhashed(old))) {
> + iput(old);
> + goto again;
> + }
> + return old;
> + }
> +
> + if (unlikely(set(inode, data))) {
> + inode = NULL;
> + goto unlock;
> + }
> +
> + /*
> + * Return the locked inode with I_NEW set, the
> + * caller is responsible for filling in the contents
> + */
> + spin_lock(&inode->i_lock);
> + inode->i_state = I_NEW;
> + hlist_add_head(&inode->i_hash, head);
> + spin_unlock(&inode->i_lock);
> + inode_sb_list_add(inode);
> +unlock:
> + spin_unlock(&inode_hash_lock);
> +
> + return inode;
> +}
> +EXPORT_SYMBOL(iget5_prealloc);
> +
> /**
> * iget5_locked - obtain an inode from a mounted file system
> * @sb: super block of file system
> @@ -1026,66 +1072,18 @@ struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
> int (*test)(struct inode *, void *),
> int (*set)(struct inode *, void *), void *data)
> {
> - struct hlist_head *head = inode_hashtable + hash(sb, hashval);
> - struct inode *inode;
> -again:
> - spin_lock(&inode_hash_lock);
> - inode = find_inode(sb, head, test, data);
> - spin_unlock(&inode_hash_lock);
> + struct inode *inode = ilookup5(sb, hashval, test, data);
>
> - if (inode) {
> - wait_on_inode(inode);
> - if (unlikely(inode_unhashed(inode))) {
> - iput(inode);
> - goto again;
> - }
> - return inode;
> - }
> -
> - inode = alloc_inode(sb);
> - if (inode) {
> - struct inode *old;
> -
> - spin_lock(&inode_hash_lock);
> - /* We released the lock, so.. */
> - old = find_inode(sb, head, test, data);
> - if (!old) {
> - if (set(inode, data))
> - goto set_failed;
> -
> - spin_lock(&inode->i_lock);
> - inode->i_state = I_NEW;
> - hlist_add_head(&inode->i_hash, head);
> - spin_unlock(&inode->i_lock);
> - inode_sb_list_add(inode);
> - spin_unlock(&inode_hash_lock);
> -
> - /* Return the locked inode with I_NEW set, the
> - * caller is responsible for filling in the contents
> - */
> - return inode;
> - }
> + if (!inode) {
> + struct inode *new = alloc_inode(sb);
>
> - /*
> - * Uhhuh, somebody else created the same inode under
> - * us. Use the old inode instead of the one we just
> - * allocated.
> - */
> - spin_unlock(&inode_hash_lock);
> - destroy_inode(inode);
> - inode = old;
> - wait_on_inode(inode);
> - if (unlikely(inode_unhashed(inode))) {
> - iput(inode);
> - goto again;
> + if (new) {
> + inode = iget5_prealloc(new, sb, hashval, test, set, data);
> + if (inode != new)
> + destroy_inode(new);
> }
> }
> return inode;
> -
> -set_failed:
> - spin_unlock(&inode_hash_lock);
> - destroy_inode(inode);
> - return NULL;
> }
> EXPORT_SYMBOL(iget5_locked);
>
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