GFS2: Drop inadequate rgrps from the reservation tree

This is just basically a resend of a patch I posted earlier.
It didn't change from its original, except in diff offsets, etc:

This patch fixes a bug in the GFS2 block allocation code. The problem
starts if a process already has a multi-block reservation, but for
some reason, another process disqualifies it from further allocations.
For example, the other process might set on the GFS2_RDF_ERROR bit.
The process holding the reservation jumps to label skip_rgrp, but
that label comes after the code that removes the reservation from the
tree. Therefore, the no longer usable reservation is not removed from
the rgrp's reservations tree; it's lost. Eventually, the lost reservation
causes the count of reserved blocks to get off, and eventually that
causes a BUG_ON(rs->rs_rbm.rgd->rd_reserved < rs->rs_free) to trigger.
This patch moves the call to after label skip_rgrp so that the
disqualified reservation is properly removed from the tree, thus keeping
the rgrp rd_reserved count sane.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 809fecd8297038f94f35e4935cc068e265c67f7d..1ccf89ab42b676c4abd7047819074316c9255fc8 100644 (file)
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1944,15 +1944,16 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
                        return 0;
                }
 
-               /* Drop reservation, if we couldn't use reserved rgrp */
-               if (gfs2_rs_active(rs))
-                       gfs2_rs_deltree(rs);
 check_rgrp:
                /* Check for unlinked inodes which can be reclaimed */
                if (rs->rs_rbm.rgd->rd_flags & GFS2_RDF_CHECK)
                        try_rgrp_unlink(rs->rs_rbm.rgd, &last_unlinked,
                                        ip->i_no_addr);
 skip_rgrp:
+               /* Drop reservation, if we couldn't use reserved rgrp */
+               if (gfs2_rs_active(rs))
+                       gfs2_rs_deltree(rs);
+
                /* Unlock rgrp if required */
                if (!rg_locked)
                        gfs2_glock_dq_uninit(&rs->rs_rgd_gh);