erofs: fix deadlock when shrink erofs slab
We observed the following deadlock in the stress test under low memory scenario: Thread A Thread B - erofs_shrink_scan - erofs_try_to_release_workgroup - erofs_workgroup_try_to_freeze -- A - z_erofs_do_read_page - z_erofs_collection_begin - z_erofs_register_collection - erofs_insert_workgroup - xa_lock(&sbi->managed_pslots) -- B - erofs_workgroup_get - erofs_wait_on_workgroup_freezed -- A - xa_erase - xa_lock(&sbi->managed_pslots) -- B To fix this, it needs to hold xa_lock before freezing the workgroup since xarray will be touched then. So let's hold the lock before accessing each workgroup, just like what we did with the radix tree befo...
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13605725
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