Messages in this thread Patch in this message | | | Subject | [patch 13/18] remap_file_pages protection support: optimize install_file_pte and avoid redundant pte_file PTE's | From | blaisorblade@yahoo ... | Date | Fri, 26 Aug 2005 18:53:49 +0200 |
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
For linear uniform shared VMA's, there is no need to install pte_file PTEs to remember the offset. For private ones, the same holds for absent and pte_file PTEs, while existing ones must be left there.
I've also added some warnings on the path which used to cope with such PTE's. I expect to remove that path soon, and I've never seen that warning triggering during testing.
If we're going to refuse remap_file_pages() and MAP_POPULATE on private VMA, this patch may be further simplified.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> ---
linux-2.6.git-paolo/mm/fremap.c | 14 ++++++++++++-- linux-2.6.git-paolo/mm/memory.c | 5 +++++ 2 files changed, 17 insertions(+), 2 deletions(-)
diff -puN mm/fremap.c~rfp-linear-optim-v4 mm/fremap.c --- linux-2.6.git/mm/fremap.c~rfp-linear-optim-v4 2005-08-25 12:59:23.000000000 +0200 +++ linux-2.6.git-paolo/mm/fremap.c 2005-08-25 12:59:23.000000000 +0200 @@ -129,6 +129,12 @@ int install_file_pte(struct mm_struct *m BUG_ON(!uniform && !(vma->vm_flags & VM_SHARED)); + /* We're being called by mmap(MAP_NONBLOCK|MAP_POPULATE) on an uniform + * shared VMA. So don't need to take the lock, and to install a PTE for + * the page we'd fault in anyway. */ + if (uniform && (vma->vm_flags & VM_SHARED)) + return 0; + pgd = pgd_offset(mm, addr); spin_lock(&mm->page_table_lock); @@ -150,14 +156,18 @@ int install_file_pte(struct mm_struct *m if (uniform && pte_none(*pte)) goto err_unlock; + err = 0; zap_pte(mm, vma, addr, pte); + /* I don't want at all to install useless pte_file pte's for private + * mappings. */ + if (unlikely(uniform)) + goto err_unlock; + set_pte_at(mm, addr, pte, pgoff_prot_to_pte(pgoff, pgprot)); pte_val = *pte; pte_unmap(pte); update_mmu_cache(vma, addr, pte_val); - spin_unlock(&mm->page_table_lock); - return 0; err_unlock: spin_unlock(&mm->page_table_lock); diff -puN mm/memory.c~rfp-linear-optim-v4 mm/memory.c --- linux-2.6.git/mm/memory.c~rfp-linear-optim-v4 2005-08-25 12:59:23.000000000 +0200 +++ linux-2.6.git-paolo/mm/memory.c 2005-08-25 12:59:23.000000000 +0200 @@ -1983,10 +1983,15 @@ static int do_file_page(struct mm_struct /* * Fall back to the linear mapping if the fs does not support * ->populate; in this case do the protection checks. + * Could have been installed by install_file_pte, for a MAP_NONBLOCK + * pagetable population. */ if (!vma->vm_ops->populate || ((access_mask & (VM_WRITE|VM_MAYWRITE)) && !(vma->vm_flags & VM_SHARED))) { + /* remap_file_pages should disallow this, now that + * install_file_pte skips linear ones. */ + WARN_ON(1); /* We're behaving as if pte_file was cleared, so check * protections like in handle_pte_fault. */ if (check_perms(vma, access_mask)) _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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