On Wed, 18 Mar 2015, Kirill A. Shutemov wrote: > On Wed, Mar 18, 2015 at 11:16:42AM -0400, Mikulas Patocka wrote: > > Hi > > > > Here I'm sending a patch that fixes numerous "BUG: non-zero nr_pmds on > > freeing mm: -1" errors on 64-bit PA-RISC kernel. > > > > I think the patch posted here > > http://www.spinics.net/lists/linux-parisc/msg05981.html is incorrect, it > > wouldn't work if the affected address range is freed and allocated > > multiple times. > > - 1. alloc pgd with built-in pmd, the count of pmds is 1 > > - 2. free the range covered by the built-in pmd, the count of pmds > > is 0, but the built-in pmd is still present > > Hm. Okay. I didn't realize you have special case in pmd_clear() for these > pmds. > > What about adding mm_inc_nr_pmds() in pmd_clear() for PxD_FLAG_ATTACHED > to compensate mm_dec_nr_pmds() in free_pmd_range()? pmd_clear clears one entry in the pmd, it wouldn't work. You need to add it to pgd_clear. That clears the pointer to the pmd (and does nothing if it is asked to clear the pointer to the preallocated pmd). But pgd_clear doesn't receive the pointer to mm. > I don't like pmd_preallocated() in generic code. It's too specific to > parisc. The question is if it is better to use pmd_preallocated, or pass the pointer to the mm to pgd_clear (that would affect all architectures). Mikulas -- 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>