From: Long Li leo.lilong@huawei.com
commit 07afd3173d0c6d24a47441839a835955ec6cf0d4 upstream.
Take mp->m_perag_lock for deletions from the perag radix tree in xfs_initialize_perag to prevent racing with tagging operations. Lookups are fine - they are RCU protected so already deal with the tree changing shape underneath the lookup - but tagging operations require the tree to be stable while the tags are propagated back up to the root.
Right now there's nothing stopping radix tree tagging from operating while a growfs operation is progress and adding/removing new entries into the radix tree.
Hence we can have traversals that require a stable tree occurring at the same time we are removing unused entries from the radix tree which causes the shape of the tree to change.
Likely this hasn't caused a problem in the past because we are only doing append addition and removal so the active AG part of the tree is not changing shape, but that doesn't mean it is safe. Just making the radix tree modifications serialise against each other is obviously correct.
Signed-off-by: Long Li leo.lilong@huawei.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: "Darrick J. Wong" djwong@kernel.org Signed-off-by: Chandan Babu R chandanbabu@kernel.org Signed-off-by: Catherine Hoang catherine.hoang@oracle.com Acked-by: Darrick J. Wong djwong@kernel.org --- fs/xfs/libxfs/xfs_ag.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c index f9f4d694640d..cc10a3ca052f 100644 --- a/fs/xfs/libxfs/xfs_ag.c +++ b/fs/xfs/libxfs/xfs_ag.c @@ -424,13 +424,17 @@ xfs_initialize_perag(
out_remove_pag: xfs_defer_drain_free(&pag->pag_intents_drain); + spin_lock(&mp->m_perag_lock); radix_tree_delete(&mp->m_perag_tree, index); + spin_unlock(&mp->m_perag_lock); out_free_pag: kmem_free(pag); out_unwind_new_pags: /* unwind any prior newly initialized pags */ for (index = first_initialised; index < agcount; index++) { + spin_lock(&mp->m_perag_lock); pag = radix_tree_delete(&mp->m_perag_tree, index); + spin_unlock(&mp->m_perag_lock); if (!pag) break; xfs_buf_hash_destroy(pag);