From bf3acae1ba3a2c5011591d3334e316b7a11ea7c9 Mon Sep 17 00:00:00 2001 From: Long Li Date: Mon, 15 Apr 2024 16:07:40 -0700 Subject: [PATCH] xfs: add lock protection when remove perag from radix tree Source kernel commit: 07afd3173d0c6d24a47441839a835955ec6cf0d4 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 Reviewed-by: Christoph Hellwig Reviewed-by: "Darrick J. Wong" Signed-off-by: Chandan Babu R Reviewed-by: Bill O'Donnell --- libxfs/xfs_ag.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/libxfs/xfs_ag.c b/libxfs/xfs_ag.c index bdb8a08bb..1dbc01b97 100644 --- a/libxfs/xfs_ag.c +++ b/libxfs/xfs_ag.c @@ -422,13 +422,17 @@ 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); -- 2.39.5