ublk: fix maple tree lockdep warning and cleanup#763
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ublk_buf_cleanup() iterates the maple tree with mas_for_each() without holding mas_lock, triggering a lockdep splat on CONFIG_PROVE_RCU kernels since mas_find() internally uses rcu_dereference_check() which requires either RCU or the tree lock. Fix by holding mas_lock around the iteration, and call mas_erase() before freeing each range to avoid dangling pointers in the tree. Fixes: 5e86443 ("ublk: replace xarray with IDA for shmem buffer index allocation") Reported-by: Jens Axboe <[email protected]> Closes: https://lore.kernel.org/linux-block/[email protected]/ Signed-off-by: Ming Lei <[email protected]>
Extract the shared walk+erase+unpin+kfree loop into ublk_shmem_remove_ranges(). When buf_index >= 0, only ranges matching that index are removed; when buf_index < 0, all ranges are removed. Also extract ublk_unpin_range_pages() to share the page unpinning loop. Convert both __ublk_ctrl_unreg_buf() and ublk_buf_cleanup() to use the new helper. Signed-off-by: Ming Lei <[email protected]>
ublk_shmem_remove_ranges() calls unpin_user_pages() while holding the maple tree spinlock (mas_lock). Although unpin_user_pages() is safe in atomic context, holding the spinlock across potentially many page unpinning operations is not ideal. Split into __ublk_shmem_remove_ranges() which erases up to 64 ranges under mas_lock, collecting base_pfn and nr_pages into a temporary xarray. Then drop the lock and unpin pages outside spinlock context. ublk_shmem_remove_ranges() loops until all matching ranges are processed. Signed-off-by: Ming Lei <[email protected]>
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Pull request for series with
subject: ublk: fix maple tree lockdep warning and cleanup
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1084496