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SubjectRe: [V2] btrfs: drop inode reference count on error path
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On 18.04.19 г. 14:06 ч., Pan Bian wrote:
> The reference count of inode is incremented by ihold. It should be
> dropped if not used. However, the reference count is not dropped if
> error occurs during updating the inode or deleting orphan items. This
> patch fixes the bug.
>
> Signed-off-by: Pan Bian <bianpan2016@163.com>
> ---
> V2: move ihold just before device_initialize to make code clearer
> ---
> fs/btrfs/inode.c | 54 +++++++++++++++++++++++++-----------------------------
> 1 file changed, 25 insertions(+), 29 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 82fdda8..d6630df 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -6579,7 +6579,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
> struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> u64 index;
> int err;
> - int drop_inode = 0;
> + int log_mode;
>
> /* do not allow sys_link's with other subvols of the same device */
> if (root->root_key.objectid != BTRFS_I(inode)->root->root_key.objectid)
> @@ -6616,41 +6616,37 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
> err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry, BTRFS_I(inode),
> 1, index);
>
> - if (err) {
> - drop_inode = 1;
> - } else {
> - struct dentry *parent = dentry->d_parent;
> - int ret;
> + if (err)
> + goto err_link;
>
> - err = btrfs_update_inode(trans, root, inode);
> + err = btrfs_update_inode(trans, root, inode);
> + if (err)
> + goto err_link;
> + if (inode->i_nlink == 1) {
> + /*
> + * If new hard link count is 1, it's a file created
> + * with open(2) O_TMPFILE flag.
> + */
> + err = btrfs_orphan_del(trans, BTRFS_I(inode));
> if (err)
> - goto fail;
> - if (inode->i_nlink == 1) {
> - /*
> - * If new hard link count is 1, it's a file created
> - * with open(2) O_TMPFILE flag.
> - */
> - err = btrfs_orphan_del(trans, BTRFS_I(inode));
> - if (err)
> - goto fail;
> - }
> - BTRFS_I(inode)->last_link_trans = trans->transid;
> - d_instantiate(dentry, inode);
> - ret = btrfs_log_new_name(trans, BTRFS_I(inode), NULL, parent,
> - true, NULL);
> - if (ret == BTRFS_NEED_TRANS_COMMIT) {
> - err = btrfs_commit_transaction(trans);
> - trans = NULL;
> - }
> + goto err_link;
> + }
> + BTRFS_I(inode)->last_link_trans = trans->transid;
> + ihold(inode);
> + d_instantiate(dentry, inode);
> + log_mode = btrfs_log_new_name(trans, BTRFS_I(inode), NULL,
> + dentry->d_parent, true, NULL);
> + if (log_mode == BTRFS_NEED_TRANS_COMMIT) {
> + err = btrfs_commit_transaction(trans);
> + trans = NULL;
> }
>
> +err_link:
> + if (err)
> + inode_dec_link_count(inode);

Any particular reason why you moved this before ending the transaction?
It potentially has an effect during tyransaction commit since doing
inode_dec_link_count does mark_inode_dirty which moves the inode on the
dirty list. Have you explicitly thought about that ? Note, I'm not
saying it's wrong but I want the rationale for the code move.

> fail:
> if (trans)
> btrfs_end_transaction(trans);
> - if (drop_inode) {
> - inode_dec_link_count(inode);
> - iput(inode);
> - }
> btrfs_btree_balance_dirty(fs_info);
> return err;
> }
>

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