maple_tree: add mas_is_active() to detect in-tree walks
Patch series "maple_tree: Fix mas_prev() state regression". Pedro Falcato retported an mprotect regression [1] which was bisected back to the iterator changes for maple tree. Root cause analysis showed the mas_prev() running off the end of the VMA space (previous from 0) followed by mas_find(), would skip the first value. This patchset introduces maple state underflow/overflow so the sequence of calls on the maple state will return what the user expects. Users who encounter this bug may see mprotect(), userfaultfd_register(), and mlock() fail on VMAs mapped with address 0. This patch (of 2): Instead of constantly checking each possibility of the maple state, create a fast path that will skip over checking unlikely states. Link: https://lkml.kernel.org/r/20230921181236.509072-1-Liam.Howlett@oracle.com Link: https://lkml.kernel.org/r/20230921181236.509072-2-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Pedro Falcato <pedro.falcato@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -511,6 +511,15 @@ static inline bool mas_is_paused(const struct ma_state *mas)
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return mas->node == MAS_PAUSE;
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}
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/* Check if the mas is pointing to a node or not */
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static inline bool mas_is_active(struct ma_state *mas)
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{
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if ((unsigned long)mas->node >= MAPLE_RESERVED_RANGE)
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return true;
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return false;
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}
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/**
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* mas_reset() - Reset a Maple Tree operation state.
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* @mas: Maple Tree operation state.
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