On Tue, 2013-07-16 at 10:54 +1000, Dave Chinner wrote:
> 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....
I see.
Is it ok if the error reason is not propagated to the xlog_write() code
path ?
>
> Cheers,
>
> Dave.
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