Le 06/03/2024 à 11:41, peterx@xxxxxxxxxx a écrit : > From: Peter Xu <peterx@xxxxxxxxxx> > > [based on akpm/mm-unstable latest commit a7f399ae964e] > > In previous work [1], we removed the pXd_large() API, which is arch > specific. This patchset further removes the hugetlb pXd_huge() API. > > Hugetlb was never special on creating huge mappings when compared with > other huge mappings. Having a standalone API just to detect such pgtable > entries is more or less redundant, especially after the pXd_leaf() API set > is introduced with/without CONFIG_HUGETLB_PAGE. > > When looking at this problem, a few issues are also exposed that we don't > have a clear definition of the *_huge() variance API. This patchset > started by cleaning these issues first, then replace all *_huge() users to > use *_leaf(), then drop all *_huge() code. > > On x86/sparc, swap entries will be reported "true" in pXd_huge(), while for > all the rest archs they're reported "false" instead. This part is done in > patch 1-5, in which I suspect patch 1 can be seen as a bug fix, but I'll > leave that to hmm experts to decide. > > Besides, there are three archs (arm, arm64, powerpc) that have slightly > different definitions between the *_huge() v.s. *_leaf() variances. I > tackled them separately so that it'll be easier for arch experts to chim in > when necessary. This part is done in patch 6-9. > > The final patches 10-13 do the rest on the final removal, since *_leaf() > will be the ultimate API in the future, and we seem to have quite some > confusions on how *_huge() APIs can be defined, provide a rich comment for > *_leaf() API set to define them properly to avoid future misuse, and > hopefully that'll also help new archs to start support huge mappings and > avoid traps (like either swap entries, or PROT_NONE entry checks). > > The whole series is only lightly tested on x86, while as usual I don't have > the capability to test all archs that it touches. > > Marking this series RFC as of now. > > [1] https://lore.kernel.org/r/20240305043750.93762-1-peterx@xxxxxxxxxx > Hi Peter, and nice job you are doing in cleaning up things around _huge stuff. One thing that might be worth looking at also at some point is the mess around pmd_clear_huge() and pud_clear_huge(). I tried to clean things up with commit c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge") but it was reverted because of arm64 by commit d8a719059b9d ("Revert "mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge"") So now powerpc/8xx has to implement pmd_clear_huge() and pud_clear_huge() allthough 8xx page hierarchy only has 2 levels. Christophe
