xfs: fix fsmap for internal zoned devices

Filesystems with an internal zoned rt section use xfs_rtblock_t values
that are relative to the start of the data device.  When fsmap reports
on internal rt sections, it reports the space used by the data section
as "OWN_FS".

Unfortunately, the logic for resuming a query isn't quite right, so
xfs/273 fails because it stress-tests GETFSMAP with a single-record
buffer.  If we enter the "report fake space as OWN_FS" block with a
nonzero key[0].fmr_length, we should add that to key[0].fmr_physical
and recheck if we still need to emit the fake record.  We should /not/
just return 0 from the whole function because that prevents all rmap
record iteration.

If we don't enter that block, the resumption is still wrong.
keys[*].fmr_physical is a reflection of what we copied out to userspace
on a previous query, which means that it already accounts for rgstart.
It is not correct to add rtstart_daddr when computing start_rtb or
end_rtb, so stop that.

While we're at it, add a xfs_has_zoned to make it clear that this is a
zoned filesystem thing.

Fixes: e50ec7fac81aa2 ("xfs: enable fsmap reporting for internal RT devices")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index a4bc1642fe5615793c2ee611a34a61f1963118e8..414b27a86458864b048fc978f51fee05679df0cf 100644 (file)
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -876,6 +876,7 @@ xfs_getfsmap_rtdev_rmapbt(
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
 {
+       struct xfs_fsmap                key0 = *keys; /* struct copy */
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_rtgroup              *rtg = NULL;
        struct xfs_btree_cur            *bt_cur = NULL;
@@ -887,32 +888,46 @@ xfs_getfsmap_rtdev_rmapbt(
        int                             error = 0;
 
        eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rtstart + mp->m_sb.sb_rblocks);
-       if (keys[0].fmr_physical >= eofs)
+       if (key0.fmr_physical >= eofs)
                return 0;
 
+       /*
+        * On zoned filesystems with an internal rt volume, the volume comes
+        * immediately after the end of the data volume.  However, the
+        * xfs_rtblock_t address space is relative to the start of the data
+        * device, which means that the first @rtstart fsblocks do not actually
+        * point anywhere.  If a fsmap query comes in with the low key starting
+        * below @rtstart, report it as "owned by filesystem".
+        */
        rtstart_daddr = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rtstart);
-       if (keys[0].fmr_physical < rtstart_daddr) {
+       if (xfs_has_zoned(mp) && key0.fmr_physical < rtstart_daddr) {
                struct xfs_fsmap_irec           frec = {
                        .owner                  = XFS_RMAP_OWN_FS,
                        .len_daddr              = rtstart_daddr,
                };
 
-               /* Adjust the low key if we are continuing from where we left off. */
-               if (keys[0].fmr_length > 0) {
-                       info->low_daddr = keys[0].fmr_physical + keys[0].fmr_length;
-                       return 0;
+               /*
+                * Adjust the start of the query range if we're picking up from
+                * a previous round, and only emit the record if we haven't
+                * already gone past.
+                */
+               key0.fmr_physical += key0.fmr_length;
+               if (key0.fmr_physical < rtstart_daddr) {
+                       error = xfs_getfsmap_helper(tp, info, &frec);
+                       if (error)
+                               return error;
+
+                       key0.fmr_physical = rtstart_daddr;
                }
 
-               /* Fabricate an rmap entry for space occupied by the data dev */
-               error = xfs_getfsmap_helper(tp, info, &frec);
-               if (error)
-                       return error;
+               /* Zero the other fields to avoid further adjustments. */
+               key0.fmr_owner = 0;
+               key0.fmr_offset = 0;
+               key0.fmr_length = 0;
        }
 
-       start_rtb = xfs_daddr_to_rtb(mp, rtstart_daddr + keys[0].fmr_physical);
-       end_rtb = xfs_daddr_to_rtb(mp, rtstart_daddr +
-                       min(eofs - 1, keys[1].fmr_physical));
-
+       start_rtb = xfs_daddr_to_rtb(mp, key0.fmr_physical);
+       end_rtb = xfs_daddr_to_rtb(mp, min(eofs - 1, keys[1].fmr_physical));
        info->missing_owner = XFS_FMR_OWN_FREE;
 
        /*
@@ -920,12 +935,12 @@ xfs_getfsmap_rtdev_rmapbt(
         * low to the fsmap low key and max out the high key to the end
         * of the rtgroup.
         */
-       info->low.rm_offset = XFS_BB_TO_FSBT(mp, keys[0].fmr_offset);
-       error = xfs_fsmap_owner_to_rmap(&info->low, &keys[0]);
+       info->low.rm_offset = XFS_BB_TO_FSBT(mp, key0.fmr_offset);
+       error = xfs_fsmap_owner_to_rmap(&info->low, &key0);
        if (error)
                return error;
-       info->low.rm_blockcount = XFS_BB_TO_FSBT(mp, keys[0].fmr_length);
-       xfs_getfsmap_set_irec_flags(&info->low, &keys[0]);
+       info->low.rm_blockcount = XFS_BB_TO_FSBT(mp, key0.fmr_length);
+       xfs_getfsmap_set_irec_flags(&info->low, &key0);
 
        /* Adjust the low key if we are continuing from where we left off. */
        if (info->low.rm_blockcount == 0) {