On Mon, Jul 15, 2013 at 05:52:34PM -0500, Chandra Seetharaman wrote:
> While testing and rearranging my pquota/gquota code, I stumbled
> on a xfs_shutdown() during a mount. But the mount just hung.
>
> I debugged and found that there is a deadlock involving
> &log->l_cilp->xc_ctx_lock.
>
> It is in a code path where &log->l_cilp->xc_ctx_lock is first
> acquired in read mode and some levels down the same semaphore
> is being acquired in write mode causing a deadlock.
>
> This is the stack:
> xfs_log_commit_cil -> acquires &log->l_cilp->xc_ctx_lock in read mode
> xlog_print_tic_res
> xfs_force_shutdown
> xfs_log_force_umount
> xlog_cil_force
> xlog_cil_force_lsn
> xlog_cil_push_foreground
> xlog_cil_push - tries to acquire same semaphore in write mode
>
> This patch fixes the deadlock by not calling xfs_force_shutdown() while
> holding the semaphore, instead calling it after dropping teh semaphore.
>
> Thanks to Dave for suggesting this solution.
>
> Signed-off-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
>
> ---
> fs/xfs/xfs_log.c | 6 +++---
> fs/xfs/xfs_log_cil.c | 10 ++++++----
> fs/xfs/xfs_log_priv.h | 2 +-
> fs/xfs/xfs_trans.c | 2 +-
> 4 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index d852a2b..b9fa2da 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1837,7 +1837,7 @@ xlog_state_finish_copy(
> * print out info relating to regions written which consume
> * the reservation
> */
> -void
> +int
> xlog_print_tic_res(
> struct xfs_mount *mp,
> struct xlog_ticket *ticket)
> @@ -1941,7 +1941,7 @@ xlog_print_tic_res(
>
> xfs_alert_tag(mp, XFS_PTAG_LOGRES,
> "xlog_write: reservation ran out. Need to up reservation");
> - xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> + return EFSCORRUPTED;
Note the "SHUTDOWN_CORRUPT_INCORE" reason given here....
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 35a2299..d96022f 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -1547,7 +1547,7 @@ xfs_trans_commit(
> xfs_trans_apply_dquot_deltas(tp);
>
> error = xfs_log_commit_cil(mp, tp, &commit_lsn, flags);
> - if (error == ENOMEM) {
> + if (error) {
> xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
Which is different to the reason given here. The shutdown reason
should be maintained for this particular error....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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