From: Bob Peterson rpeterso@redhat.com
[ Upstream commit 4f36cb36c9d14340bb200d2ad9117b03ce992cfe ]
The GFS2_RDF_UPTODATE flag in the rgrp is used to determine when a rgrp buffer is valid. It's cleared when the glock is invalidated, signifying that the buffer data is now invalid. But before this patch, function update_rgrp_lvb was setting the flag when it determined it had a valid lvb. But that's an invalid assumption: just because you have a valid lvb doesn't mean you have valid buffers. After all, another node may have made the lvb valid, and this node just fetched it from the glock via dlm.
Consider this scenario: 1. The file system is mounted with RGRPLVB option. 2. In gfs2_inplace_reserve it locks the rgrp glock EX, but thanks to GL_SKIP, it skips the gfs2_rgrp_bh_get. 3. Since loops == 0 and the allocation target (ap->target) is bigger than the largest known chunk of blocks in the rgrp (rs->rs_rbm.rgd->rd_extfail_pt) it skips that rgrp and bypasses the call to gfs2_rgrp_bh_get there as well. 4. update_rgrp_lvb sees the lvb MAGIC number is valid, so bypasses gfs2_rgrp_bh_get, but it still sets sets GFS2_RDF_UPTODATE due to this invalid assumption. 5. The next time update_rgrp_lvb is called, it sees the bit is set and just returns 0, assuming both the lvb and rgrp are both uptodate. But since this is a smaller allocation, or space has been freed by another node, thus adjusting the lvb values, it decides to use the rgrp for allocations, with invalid rd_free due to the fact it was never updated.
This patch changes update_rgrp_lvb so it doesn't set the UPTODATE flag anymore. That way, it has no choice but to fetch the latest values.
Signed-off-by: Bob Peterson rpeterso@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/gfs2/rgrp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c index 449d0cb45a845..63e5387c84d26 100644 --- a/fs/gfs2/rgrp.c +++ b/fs/gfs2/rgrp.c @@ -1227,7 +1227,7 @@ static int update_rgrp_lvb(struct gfs2_rgrpd *rgd) rl_flags = be32_to_cpu(rgd->rd_rgl->rl_flags); rl_flags &= ~GFS2_RDF_MASK; rgd->rd_flags &= GFS2_RDF_MASK; - rgd->rd_flags |= (rl_flags | GFS2_RDF_UPTODATE | GFS2_RDF_CHECK); + rgd->rd_flags |= (rl_flags | GFS2_RDF_CHECK); if (rgd->rd_rgl->rl_unlinked == 0) rgd->rd_flags &= ~GFS2_RDF_CHECK; rgd->rd_free = be32_to_cpu(rgd->rd_rgl->rl_free);