| Message ID | 20231213031013.390145-1-leo.lilong@huawei.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [v3,1/2] xfs: add lock protection when remove perag from radix tree | expand |
On Wed, Dec 13, 2023 at 11:10:12AM +0800, Long Li wrote: > 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> Looks correct to me, and I didn't find any other suspicious accesses of m_perag_tree so Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D > --- > 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 f62ff125a50a..c730976fdfc0 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); > -- > 2.31.1 > >
diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c index f62ff125a50a..c730976fdfc0 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);