On Tuesday 30 June 2020 9:12:02 PM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> xfs_trans_dqresv is the function that we use to make reservations
> against resource quotas. Each resource contains two counters: the
> q_core counter, which tracks resources allocated on disk; and the dquot
> reservation counter, which tracks how much of that resource has either
> been allocated or reserved by threads that are working on metadata
> updates.
>
> For disk blocks, we compare the proposed reservation counter against the
> hard and soft limits to decide if we're going to fail the operation.
> However, for inodes we inexplicably compare against the q_core counter,
> not the incore reservation count.
>
> Since the q_core counter is always lower than the reservation count and
> we unlock the dquot between reservation and transaction commit, this
> means that multiple threads can reserve the last inode count before we
> hit the hard limit, and when they commit, we'll be well over the hard
> limit.
>
> Fix this by checking against the incore inode reservation counter, since
> we would appear to maintain that correctly (and that's what we report in
> GETQUOTA).
>
As mentioned above, q_core.d_icount's value can be less than what has been
reserved by various running tasks. Hence deriving new reservation count from
q_core.d_icount is incorrect.
Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_trans_dquot.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>
> diff --git a/fs/xfs/xfs_trans_dquot.c b/fs/xfs/xfs_trans_dquot.c
> index c0f73b82c055..ed0ce8b301b4 100644
> --- a/fs/xfs/xfs_trans_dquot.c
> +++ b/fs/xfs/xfs_trans_dquot.c
> @@ -647,7 +647,7 @@ xfs_trans_dqresv(
> }
> }
> if (ninos > 0) {
> - total_count = be64_to_cpu(dqp->q_core.d_icount) + ninos;
> + total_count = dqp->q_res_icount + ninos;
> timer = be32_to_cpu(dqp->q_core.d_itimer);
> warns = be16_to_cpu(dqp->q_core.d_iwarns);
> warnlimit = defq->iwarnlimit;
>
>
--
chandan
