From 3f5f6321f129ad5a30aa03c99c196b4612be68a8 Mon Sep 17 00:00:00 2001 From: Or Har-Toov Date: Mon, 16 Jun 2025 11:16:03 +0300 Subject: [PATCH] IB/core: Annotate umem_mutex acquisition under fs_reclaim for lockdep MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Following the fix in the previous commit ("IB/mlx5: Fix potential deadlock in MR deregistration"), teach lockdep explicitly about the locking order between fs_reclaim and umem_mutex. The previous commit resolved a potential deadlock scenario where kzalloc(GFP_KERNEL) was called while holding umem_mutex, which could lead to reclaim and eventually invoke the MMU notifier (mlx5_ib_invalidate_range()), causing a recursive acquisition of umem_mutex. To prevent such issues from reoccurring unnoticed in future code changes, add a lockdep annotation in ib_init_umem_odp() that simulates taking umem_mutex inside a reclaim context. This makes lockdep aware of this locking dependency and ensures that future violations—such as calling kzalloc() or any memory allocator that may enter reclaim while holding umem_mutex—will immediately raise a lockdep warning. Signed-off-by: Or Har-Toov Reviewed-by: Michael Guralnik Link: https://patch.msgid.link/9d31b9d8fe1db648a9f47cec3df6b8463319dee5.1750061698.git.leon@kernel.org Signed-off-by: Leon Romanovsky --- drivers/infiniband/core/umem_odp.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c index c752ae9fad6c..b1c44ec1a3f3 100644 --- a/drivers/infiniband/core/umem_odp.c +++ b/drivers/infiniband/core/umem_odp.c @@ -76,6 +76,17 @@ static int ib_init_umem_odp(struct ib_umem_odp *umem_odp, end = ALIGN(end, page_size); if (unlikely(end < page_size)) return -EOVERFLOW; + /* + * The mmu notifier can be called within reclaim contexts and takes the + * umem_mutex. This is rare to trigger in testing, teach lockdep about + * it. + */ + if (IS_ENABLED(CONFIG_LOCKDEP)) { + fs_reclaim_acquire(GFP_KERNEL); + mutex_lock(&umem_odp->umem_mutex); + mutex_unlock(&umem_odp->umem_mutex); + fs_reclaim_release(GFP_KERNEL); + } nr_entries = (end - start) >> PAGE_SHIFT; if (!(nr_entries * PAGE_SIZE / page_size)) -- 2.50.1