On Thu, Oct 27, 2022 at 02:32:42PM -0700, Darrick J. Wong wrote: > On Fri, Oct 28, 2022 at 07:49:57AM +1100, Dave Chinner wrote: > > On Thu, Oct 27, 2022 at 10:14:14AM -0700, Darrick J. Wong wrote: > > > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > > > If we're in the middle of a deferred refcount operation and decide to > > > roll the transaction to avoid overflowing the transaction space, we need > > > to check the new agbno/aglen parameters that we're about to record in > > > the new intent. Specifically, we need to check that the new extent is > > > completely within the filesystem, and that continuation does not put us > > > into a different AG. > > > > > > If the keys of a node block are wrong, the lookup to resume an > > > xfs_refcount_adjust_extents operation can put us into the wrong record > > > block. If this happens, we might not find that we run out of aglen at > > > an exact record boundary, which will cause the loop control to do the > > > wrong thing. > > > > > > The previous patch should take care of that problem, but let's add this > > > extra sanity check to stop corruption problems sooner than later. > > > > > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > --- > > > fs/xfs/libxfs/xfs_refcount.c | 48 ++++++++++++++++++++++++++++++++++++++++-- > > > 1 file changed, 46 insertions(+), 2 deletions(-) > > > > > > > > > diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c > > > index 831353ba96dc..c6aa832a8713 100644 > > > --- a/fs/xfs/libxfs/xfs_refcount.c > > > +++ b/fs/xfs/libxfs/xfs_refcount.c > > > @@ -1138,6 +1138,44 @@ xfs_refcount_finish_one_cleanup( > > > xfs_trans_brelse(tp, agbp); > > > } > > > > > > +/* > > > + * Set up a continuation a deferred refcount operation by updating the intent. > > > + * Checks to make sure we're not going to run off the end of the AG. > > > + */ > > > +static inline int > > > +xfs_refcount_continue_op( > > > + struct xfs_btree_cur *cur, > > > + xfs_fsblock_t startblock, > > > + xfs_agblock_t new_agbno, > > > + xfs_extlen_t new_len, > > > + xfs_fsblock_t *fsbp) > > > +{ > > > + struct xfs_mount *mp = cur->bc_mp; > > > + struct xfs_perag *pag = cur->bc_ag.pag; > > > + xfs_fsblock_t new_fsbno; > > > + xfs_agnumber_t old_agno; > > > + > > > + old_agno = XFS_FSB_TO_AGNO(mp, startblock); > > > + new_fsbno = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno); > > > + > > > + /* > > > + * If we don't have any work left to do, then there's no need > > > + * to perform the validation of the new parameters. > > > + */ > > > + if (!new_len) > > > + goto done; > > > > Shouldn't we be validating new_fsbno rather than just returning > > whatever we calculated here? Thinking further about this, let's elide the call if there isn't any work to continue. IOWs, the function shortens to: static inline int xfs_refcount_continue_op( struct xfs_btree_cur *cur, xfs_fsblock_t startblock, xfs_agblock_t new_agbno, xfs_extlen_t new_len, xfs_fsblock_t *fsbp) { struct xfs_mount *mp = cur->bc_mp; struct xfs_perag *pag = cur->bc_ag.pag; xfs_fsblock_t new_fsbno; new_fsbno = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno); if (XFS_IS_CORRUPT(mp, !xfs_verify_fsbext(mp, new_fsbno, new_len))) return -EFSCORRUPTED; if (XFS_IS_CORRUPT(mp, pag->pag_agno != XFS_FSB_TO_AGNO(mp, new_fsbno))) return -EFSCORRUPTED; *fsbp = new_fsbno; return 0; } and the call sites now look like: error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno, new_len, XFS_REFCOUNT_ADJUST_INCREASE); if (error) goto out_drop; if (*new_len > 0) error = xfs_refcount_continue_op(rcur, startblock, new_agbno, *new_len, new_fsb); --D > No. Imagine that the deferred work is performed against the last 30 > blocks of the last AG in the filesystem. Let's say that the last AG is > AG 3 and the AG has 100 blocks. fsblock 3:99 is the last fsblock in the > filesystem. > > Before we start the deferred work, startblock == 3:70 and > blockcount == 30. We adjust the refcount of those 30 blocks, so we're > done now. The adjust function passes out new_agbno == 70 + 30 and > new_len == 30 - 30. > > The agbno to fsbno conversion sets new_fsbno to 3:100 and new_len is 0. > However, fsblock 3/100 is one block past the end of both AG 3 and the > filesystem, so the check below will fail: > > > > + if (XFS_IS_CORRUPT(mp, !xfs_verify_fsbext(mp, new_fsbno, new_len))) > > > + return -EFSCORRUPTED; > > > + > > > + if (XFS_IS_CORRUPT(mp, old_agno != XFS_FSB_TO_AGNO(mp, new_fsbno))) > > > + return -EFSCORRUPTED; > > > > We already know what agno new_fsbno sits in - we calculated it > > directly from pag->pag_agno above, so this can jsut check against > > pag->pag_agno directly, right? > > We don't actually know what agno new_fsbno sits in because of the way > that the agblock -> fsblock conversion works: > > #define XFS_AGB_TO_FSB(mp,agno,agbno) \ > (((xfs_fsblock_t)(agno) << (mp)->m_sb.sb_agblklog) | (agbno)) > > Notice how we don't mask off the bits of agbno above sb_agblklog? If > sb_agblklog is (say) 20 but agbno has bit 31 set, that bit 31 will bump > the AG number by 2^11 AGs. > > The genesis of this patch was from the old days when rc_startblock had > bit 31 set on COW staging extents. Splitting out the cow/shared domain > later in the series makes this patch sort of redundant, but I still want > to catch the cases where agbno has some bit set above agblklog due to > corruption/bitflips/shenanigans. > > > i.e. > > > > if (XFS_IS_CORRUPT(mp, > > XFS_FSB_TO_AGNO(mp, startblock) != pag->pag_agno)) > > return -EFSCORRUPTED; > > > > and we don't need the local variable for it.... > > Not quite -- we need to compare new_fsbno's agnumber against the perag > structure. But you're right that @old_agno isn't necessary. > > if (XFS_IS_CORRUPT(mp, > XFS_FSB_TO_AGNO(mp, new_fsbno) != pag->pag_agno)) > /* fail */ > > I'll change it to the above. > > --D > > > Cheers, > > > > Dave. > > > > -- > > Dave Chinner > > david@xxxxxxxxxxxxx