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Wong" , Dave Chinner , Christoph Hellwig , Eric Sandeen Subject: Re: [PATCH v8 4/5] xfs: support shrinking unused space in the last AG Message-ID: <20210322120722.GC2000812@xiangao.remote.csb> References: <20210305025703.3069469-1-hsiangkao@redhat.com> <20210305025703.3069469-5-hsiangkao@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Mar 22, 2021 at 07:30:40AM -0400, Brian Foster wrote: > On Fri, Mar 05, 2021 at 10:57:02AM +0800, Gao Xiang wrote: > > As the first step of shrinking, this attempts to enable shrinking > > unused space in the last allocation group by fixing up freespace > > btree, agi, agf and adjusting super block and use a helper > > xfs_ag_shrink_space() to fixup the last AG. > > > > This can be all done in one transaction for now, so I think no > > additional protection is needed. > > > > Reviewed-by: Darrick J. Wong > > Signed-off-by: Gao Xiang > > --- > > fs/xfs/xfs_fsops.c | 88 ++++++++++++++++++++++++++++------------------ > > fs/xfs/xfs_trans.c | 1 - > > 2 files changed, 53 insertions(+), 36 deletions(-) > > > > diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c > > index fc9e799b2ae3..71cba61a451c 100644 > > --- a/fs/xfs/xfs_fsops.c > > +++ b/fs/xfs/xfs_fsops.c > > @@ -91,23 +91,28 @@ xfs_growfs_data_private( > > xfs_agnumber_t nagcount; > > xfs_agnumber_t nagimax = 0; > > xfs_rfsblock_t nb, nb_div, nb_mod; > > - xfs_rfsblock_t delta; > > + int64_t delta; > > bool lastag_resetagres; > > xfs_agnumber_t oagcount; > > struct xfs_trans *tp; > > struct aghdr_init_data id = {}; > > > > nb = in->newblocks; > > - if (nb < mp->m_sb.sb_dblocks) > > - return -EINVAL; > > - if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb))) > > + if (nb == mp->m_sb.sb_dblocks) > > + return 0; > > It looks like the caller already does this check. yeah, will remove it. Thanks for pointing out. > > > + > > + error = xfs_sb_validate_fsb_count(&mp->m_sb, nb); > > + if (error) > > return error; > > - error = xfs_buf_read_uncached(mp->m_ddev_targp, > > + > > + if (nb > mp->m_sb.sb_dblocks) { > > + error = xfs_buf_read_uncached(mp->m_ddev_targp, > > XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1), > > XFS_FSS_TO_BB(mp, 1), 0, &bp, NULL); > > - if (error) > > - return error; > > - xfs_buf_relse(bp); > > + if (error) > > + return error; > > + xfs_buf_relse(bp); > > + } > > > > nb_div = nb; > > nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks); > > @@ -115,10 +120,15 @@ xfs_growfs_data_private( > > if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) { > > nagcount--; > > nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks; > > - if (nb < mp->m_sb.sb_dblocks) > > - return -EINVAL; > > } > > delta = nb - mp->m_sb.sb_dblocks; > > + /* > > + * XFS doesn't really support single-AG filesystems, so do not > > + * permit callers to remove the filesystem's second and last AG. > > + */ > > + if (delta < 0 && nagcount < 2) > > + return -EINVAL; > > + > > What if the filesystem is already single AG? Unless I'm missing > something, we already have a check a bit further down that prevents > removal of AGs in the first place. I think it tends to forbid (return -EINVAL) shrinking the filesystem with a single AG only? Am I missing something? Thanks, Gao Xiang > > Otherwise looks reasonable.. > > Brian > > > oagcount = mp->m_sb.sb_agcount; > > > > /* allocate the new per-ag structures */ > > @@ -126,15 +136,22 @@ xfs_growfs_data_private( > > error = xfs_initialize_perag(mp, nagcount, &nagimax); > > if (error) > > return error; > > + } else if (nagcount < oagcount) { > > + /* TODO: shrinking the entire AGs hasn't yet completed */ > > + return -EINVAL; > > } > > > > error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata, > > - XFS_GROWFS_SPACE_RES(mp), 0, XFS_TRANS_RESERVE, &tp); > > + (delta > 0 ? XFS_GROWFS_SPACE_RES(mp) : -delta), 0, > > + XFS_TRANS_RESERVE, &tp); > > if (error) > > return error; > > > > - error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount, > > - delta, &lastag_resetagres); > > + if (delta > 0) > > + error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount, > > + delta, &lastag_resetagres); > > + else > > + error = xfs_ag_shrink_space(mp, &tp, nagcount - 1, -delta); > > if (error) > > goto out_trans_cancel; > > > > @@ -145,7 +162,7 @@ xfs_growfs_data_private( > > */ > > if (nagcount > oagcount) > > xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount); > > - if (delta > 0) > > + if (delta) > > xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS, delta); > > if (id.nfree) > > xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, id.nfree); > > @@ -169,28 +186,29 @@ xfs_growfs_data_private( > > xfs_set_low_space_thresholds(mp); > > mp->m_alloc_set_aside = xfs_alloc_set_aside(mp); > > > > - /* > > - * If we expanded the last AG, free the per-AG reservation > > - * so we can reinitialize it with the new size. > > - */ > > - if (lastag_resetagres) { > > - struct xfs_perag *pag; > > - > > - pag = xfs_perag_get(mp, id.agno); > > - error = xfs_ag_resv_free(pag); > > - xfs_perag_put(pag); > > - if (error) > > - return error; > > + if (delta > 0) { > > + /* > > + * If we expanded the last AG, free the per-AG reservation > > + * so we can reinitialize it with the new size. > > + */ > > + if (lastag_resetagres) { > > + struct xfs_perag *pag; > > + > > + pag = xfs_perag_get(mp, id.agno); > > + error = xfs_ag_resv_free(pag); > > + xfs_perag_put(pag); > > + if (error) > > + return error; > > + } > > + /* > > + * Reserve AG metadata blocks. ENOSPC here does not mean there > > + * was a growfs failure, just that there still isn't space for > > + * new user data after the grow has been run. > > + */ > > + error = xfs_fs_reserve_ag_blocks(mp); > > + if (error == -ENOSPC) > > + error = 0; > > } > > - > > - /* > > - * Reserve AG metadata blocks. ENOSPC here does not mean there was a > > - * growfs failure, just that there still isn't space for new user data > > - * after the grow has been run. > > - */ > > - error = xfs_fs_reserve_ag_blocks(mp); > > - if (error == -ENOSPC) > > - error = 0; > > return error; > > > > out_trans_cancel: > > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c > > index 44f72c09c203..d047f5f26cc0 100644 > > --- a/fs/xfs/xfs_trans.c > > +++ b/fs/xfs/xfs_trans.c > > @@ -434,7 +434,6 @@ xfs_trans_mod_sb( > > tp->t_res_frextents_delta += delta; > > break; > > case XFS_TRANS_SB_DBLOCKS: > > - ASSERT(delta > 0); > > tp->t_dblocks_delta += delta; > > break; > > case XFS_TRANS_SB_AGCOUNT: > > -- > > 2.27.0 > > >