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Thus ensure that the caller is aware of this by triggering = a BUG >>>>>>>> when the entry is a sibling entry. >>>>>>> Is it possible to add a test case in lib/test_xarray.c for this? >>>>>>> You can compile the tests with =E2=80=9Cmake -C tools/testing/radix= -tree=E2=80=9D >>>>>>> and run =E2=80=9C./tools/testing/radix-tree/xarray=E2=80=9D. >>>>>> Sorry forgot to Cc you. >>>>>> I can surely do that later, but does this patch look fine? >>>>> I am not sure the exact situation you are describing, so I asked you >>>>> to write a test case to demonstrate the issue. :) >>>> >>>> Suppose we have a shift-6 node having an order-9 entry =3D> 8 - 1 =3D = 7 siblings, >>>> so assume the slots are at offset 0 till 7 in this node. If xas->xa_of= fset is 6, >>>> then the code will compute order as 1 + xas->xa_node->shift =3D 7. So = I mean to >>>> say that the order computation must start from the beginning of the mu= lti-slot >>>> entries, that is, the non-sibling entry. >>> Got it. Thanks for the explanation. It will be great to add this explan= ation >>> to the commit log. >>> >>> I also notice that in the comment of xas_get_order() it says >>> =E2=80=9CCalled after xas_load()=E2=80=9D and xas_load() returns NULL o= r an internal >>> entry for a sibling. So caller is responsible to make sure xas is not p= ointing >>> to a sibling entry. It is good to have a check here. >>> >>> In terms of the patch, we are moving away from BUG()/BUG_ON(), so I won= der >>> if there is a less disruptive way of handling this. Something like retu= rn >>> -EINVAL instead with modified function comments and adding a comment >>> at the return -EIVAL saying something like caller needs to pass >>> a non-sibling entry. >> >> What's the reason for moving away from BUG_ON()? > > BUG_ON is in general a bad thing. See Documentation/process/coding-style.= rst and the history on the related changes for details. > > Here, it is less critical than it looks. > > XA_NODE_BUG_ON is only active with XA_DEBUG. > > And XA_DEBUG is only defined in > > tools/testing/shared/xarray-shared.h:#define XA_DEBUG > > So IIUC, it's only active in selftests, and completely inactive in any ke= rnel builds. Oh, I missed that. But that also means this patch becomes a nop in kernel builds. Best Regards, Yan, Zi