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IB/core: Annotate umem_mutex acquisition under fs_reclaim for lockdep

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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 <ohartoov@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Link: https://patch.msgid.link/9d31b9d8fe1db648a9f47cec3df6b8463319dee5.1750061698.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>
This commit is contained in:
Or Har-Toov 2025-06-16 11:16:03 +03:00 committed by Leon Romanovsky
parent 2ed25aa7f7
commit 3f5f6321f1
1 changed files with 11 additions and 0 deletions
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11
drivers/infiniband/core/umem_odp.c
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@ -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))