On 02/16/2016 02:00 AM, Kirill A. Shutemov wrote: > On Fri, Feb 12, 2016 at 10:33:37AM -0800, Dave Hansen wrote: >> On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote: >>> For file pages we don't deposit page table on mapping: no need to >>> withdraw it. >> >> I thought the deposit thing was to guarantee we could always do a PMD >> split. It still seems like if you wanted to split a huge-tmpfs page, >> you'd need to first split the PMD which might need the deposited one. >> >> Why not? > > For file thp, split_huge_pmd() is implemented by clearing out the pmd: we > can setup and fill pte table later. Therefore no need to deposit page > table -- we would not use it. DAX does the same. Ahh... Do we just never split in any fault contexts, or do we just retry the fault? In any case, that seems like fine enough (although subtle) behavior. Can you call it out a bit more explicitly in the patch text? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>