From 9ab72f22277487d2a3ffc8dd20fc918e186bb2b3 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 10 Aug 2021 17:00:31 -0700 Subject: xfs: fix off-by-one error when the last rt extent is in use The fsmap implementation for realtime devices uses the gap between info->next_daddr and a free rtextent reported by xfs_rtalloc_query_range to feed userspace fsmap records with an "unknown" owner. We use this trick to report to userspace when the last rtextent in the filesystem is in use by synthesizing a null rmap record starting at the next block after the query range. Unfortunately, there's a minor accounting bug in the way that we construct the null rmap record. Originally, ahigh.ar_startext contains the last rtextent for which the user wants records. It's entirely possible that number is beyond the end of the rt volume, so the location synthesized rmap record /must/ be constrained to the minimum of the high key and the number of extents in the rt volume. Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Reviewed-by: Chandan Babu R --- fs/xfs/xfs_fsmap.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c index 7d0b09c1366e..5f603ed3f678 100644 --- a/fs/xfs/xfs_fsmap.c +++ b/fs/xfs/xfs_fsmap.c @@ -523,27 +523,37 @@ xfs_getfsmap_rtdev_rtbitmap_query( { struct xfs_rtalloc_rec alow = { 0 }; struct xfs_rtalloc_rec ahigh = { 0 }; + struct xfs_mount *mp = tp->t_mountp; int error; - xfs_ilock(tp->t_mountp->m_rbmip, XFS_ILOCK_SHARED); + xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED); + /* + * Set up query parameters to return free rtextents covering the range + * we want. + */ alow.ar_startext = info->low.rm_startblock; ahigh.ar_startext = info->high.rm_startblock; - do_div(alow.ar_startext, tp->t_mountp->m_sb.sb_rextsize); - if (do_div(ahigh.ar_startext, tp->t_mountp->m_sb.sb_rextsize)) + do_div(alow.ar_startext, mp->m_sb.sb_rextsize); + if (do_div(ahigh.ar_startext, mp->m_sb.sb_rextsize)) ahigh.ar_startext++; error = xfs_rtalloc_query_range(tp, &alow, &ahigh, xfs_getfsmap_rtdev_rtbitmap_helper, info); if (error) goto err; - /* Report any gaps at the end of the rtbitmap */ + /* + * Report any gaps at the end of the rtbitmap by simulating a null + * rmap starting at the block after the end of the query range. + */ info->last = true; + ahigh.ar_startext = min(mp->m_sb.sb_rextents, ahigh.ar_startext); + error = xfs_getfsmap_rtdev_rtbitmap_helper(tp, &ahigh, info); if (error) goto err; err: - xfs_iunlock(tp->t_mountp->m_rbmip, XFS_ILOCK_SHARED); + xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED); return error; } -- cgit v1.2.3-59-g8ed1b