[PATCH 02/24] GFS2: Drop inadequate rgrps from the reservation tree

From: Steven Whitehouse
Date: Mon Jan 20 2014 - 07:24:17 EST

From: Bob Peterson <rpeterso@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Steven Whitehouse <swhiteho@xxxxxxxxxx>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 809fecd..1ccf89a 100644
--- 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 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,
+ /* 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)

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