On Fri, Feb 03, 2017 at 01:34:24PM -0500, Brian Foster wrote: > When a delalloc extent is created, it can be merged with pre-existing, > contiguous, delalloc extents. When this occurs, > xfs_bmap_add_extent_hole_delay() merges the extents along with the > associated indirect block reservations. The expectation here is that the > combined worst case indlen reservation is always less than or equal to > the indlen reservation for the individual extents. > > This is not always the case, however, as existing extents can less than > the expected indlen reservation if the extent was previously split due > to a hole punch. If a new extent merges with such an extent, the total > indlen requirement may be larger than the sum of the indlen reservations > held by both extents. > > xfs_bmap_add_extent_hole_delay() assumes that the worst case indlen > reservation is always available and assigns it to the merged extent > without consideration for the indlen held by the pre-existing extent. As > a result, the subsequent xfs_mod_fdblocks() call can attempt an > unintentional allocation rather than a free (indicated by an ASSERT() > failure). Further, if the allocation happens to fail in this context, > the failure goes unhandled and creates a filesystem wide block > accounting inconsistency. > > Fix xfs_bmap_add_extent_hole_delay() to function as designed. Cap the > indlen reservation assigned to the merged extent to the sum of the > indlen reservations held by each of the individual extents. > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --- > fs/xfs/libxfs/xfs_bmap.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c > index bfc00de..d2e48ed 100644 > --- a/fs/xfs/libxfs/xfs_bmap.c > +++ b/fs/xfs/libxfs/xfs_bmap.c > @@ -2809,7 +2809,8 @@ xfs_bmap_add_extent_hole_delay( > oldlen = startblockval(left.br_startblock) + > startblockval(new->br_startblock) + > startblockval(right.br_startblock); > - newlen = xfs_bmap_worst_indlen(ip, temp); > + newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp), > + oldlen); > xfs_bmbt_set_startblock(xfs_iext_get_ext(ifp, *idx), > nullstartblock((int)newlen)); > trace_xfs_bmap_post_update(ip, *idx, state, _THIS_IP_); > @@ -2830,7 +2831,8 @@ xfs_bmap_add_extent_hole_delay( > xfs_bmbt_set_blockcount(xfs_iext_get_ext(ifp, *idx), temp); > oldlen = startblockval(left.br_startblock) + > startblockval(new->br_startblock); > - newlen = xfs_bmap_worst_indlen(ip, temp); > + newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp), > + oldlen); > xfs_bmbt_set_startblock(xfs_iext_get_ext(ifp, *idx), > nullstartblock((int)newlen)); > trace_xfs_bmap_post_update(ip, *idx, state, _THIS_IP_); > @@ -2846,7 +2848,8 @@ xfs_bmap_add_extent_hole_delay( > temp = new->br_blockcount + right.br_blockcount; > oldlen = startblockval(new->br_startblock) + > startblockval(right.br_startblock); > - newlen = xfs_bmap_worst_indlen(ip, temp); > + newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp), > + oldlen); > xfs_bmbt_set_allf(xfs_iext_get_ext(ifp, *idx), > new->br_startoff, > nullstartblock((int)newlen), temp, right.br_state); > -- > 2.7.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
