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authorDarrick J. Wong <djwong@kernel.org>2021-08-11 03:00:31 +0300
committerDarrick J. Wong <djwong@kernel.org>2021-08-19 04:46:00 +0300
commit9ab72f22277487d2a3ffc8dd20fc918e186bb2b3 (patch)
tree47b56231c0a590417d851c0d5bf8964ec57b0aa9
parentc02f6529864a4f5f91d216d324bac4ba75415d19 (diff)
downloadlinux-9ab72f22277487d2a3ffc8dd20fc918e186bb2b3.tar.xz
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 <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
-rw-r--r--fs/xfs/xfs_fsmap.c20
1 files 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;
}