On Sun, May 23, 2021 at 06:01:33PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > The new online shrink code exposed a gap in the per-AG reservation > code, which is that we only return ENOSPC to callers if the entire fs > doesn't have enough free blocks. Except for debugging mode, the > reservation init code doesn't ever check that there's enough free space > in that AG to cover the reservation. > > Not having enough space is not considered an immediate fatal error that > requires filesystem offlining because (a) it's shouldn't be possible to > wind up in that state through normal file operations and (b) even if > one did, freeing data blocks would recover the situation. > > However, online shrink now needs to know if shrinking would not leave > enough space so that it can abort the shrink operation. Hence we need > to promote this assertion into an actual error return. > > Observed by running xfs/168 with a 1k block size, though in theory this > could happen with any configuration. > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > --- Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> > fs/xfs/libxfs/xfs_ag_resv.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > > diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c > index e32a1833d523..bbfea8022a3b 100644 > --- a/fs/xfs/libxfs/xfs_ag_resv.c > +++ b/fs/xfs/libxfs/xfs_ag_resv.c > @@ -325,10 +325,22 @@ xfs_ag_resv_init( > error2 = xfs_alloc_pagf_init(mp, tp, pag->pag_agno, 0); > if (error2) > return error2; > - ASSERT(xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved + > - xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved <= > - pag->pagf_freeblks + pag->pagf_flcount); > + > + /* > + * If there isn't enough space in the AG to satisfy the > + * reservation, let the caller know that there wasn't enough > + * space. Callers are responsible for deciding what to do > + * next, since (in theory) we can stumble along with > + * insufficient reservation if data blocks are being freed to > + * replenish the AG's free space. > + */ > + if (!error && > + xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved + > + xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved > > + pag->pagf_freeblks + pag->pagf_flcount) > + error = -ENOSPC; > } > + > return error; > } > >
