To be able to use the common 4k zero page in DAX we need to have our PTE fault path look more like our PMD fault path where a PTE entry can be marked as dirty and writeable as it is first inserted, rather than waiting for a follow-up dax_pfn_mkwrite() => finish_mkwrite_fault() call.
Right now we can rely on having a dax_pfn_mkwrite() call because we can distinguish between these two cases in do_wp_page():
case 1: 4k zero page => writable DAX storage case 2: read-only DAX storage => writeable DAX storage
This distinction is made by via vm_normal_page(). vm_normal_page() returns false for the common 4k zero page, though, just as it does for DAX ptes. Instead of special casing the DAX + 4k zero page case, we will simplify our DAX PTE page fault sequence so that it matches our DAX PMD sequence, and get rid of the dax_pfn_mkwrite() helper. We will instead use dax_iomap_fault() to handle write-protection faults.
This means that insert_pfn() needs to follow the lead of insert_pfn_pmd() and allow us to pass in a 'mkwrite' flag. If 'mkwrite' is set insert_pfn() will do the work that was previously done by wp_page_reuse() as part of the dax_pfn_mkwrite() call path.
Signed-off-by: Ross Zwisler ross.zwisler@linux.intel.com --- drivers/dax/device.c | 2 +- drivers/gpu/drm/exynos/exynos_drm_gem.c | 3 ++- drivers/gpu/drm/gma500/framebuffer.c | 2 +- drivers/gpu/drm/msm/msm_gem.c | 3 ++- drivers/gpu/drm/omapdrm/omap_gem.c | 6 ++++-- drivers/gpu/drm/ttm/ttm_bo_vm.c | 2 +- fs/dax.c | 2 +- include/linux/mm.h | 2 +- mm/memory.c | 27 +++++++++++++++++++++------ 9 files changed, 34 insertions(+), 15 deletions(-)
diff --git a/drivers/dax/device.c b/drivers/dax/device.c index e9f3b3e..3973521 100644 --- a/drivers/dax/device.c +++ b/drivers/dax/device.c @@ -273,7 +273,7 @@ static int __dev_dax_pte_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
- rc = vm_insert_mixed(vmf->vma, vmf->address, pfn); + rc = vm_insert_mixed(vmf->vma, vmf->address, pfn, false);
if (rc == -ENOMEM) return VM_FAULT_OOM; diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c index c23479b..bfa6648 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_gem.c +++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c @@ -466,7 +466,8 @@ int exynos_drm_gem_fault(struct vm_fault *vmf) }
pfn = page_to_pfn(exynos_gem->pages[page_offset]); - ret = vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV)); + ret = vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV), + false);
out: switch (ret) { diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c index 7da70b6..6dd865f 100644 --- a/drivers/gpu/drm/gma500/framebuffer.c +++ b/drivers/gpu/drm/gma500/framebuffer.c @@ -134,7 +134,7 @@ static int psbfb_vm_fault(struct vm_fault *vmf) pfn = (phys_addr >> PAGE_SHIFT);
ret = vm_insert_mixed(vma, address, - __pfn_to_pfn_t(pfn, PFN_DEV)); + __pfn_to_pfn_t(pfn, PFN_DEV), false); if (unlikely((ret == -EBUSY) || (ret != 0 && i > 0))) break; else if (unlikely(ret != 0)) { diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c index 65f3554..c187fd1 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -249,7 +249,8 @@ int msm_gem_fault(struct vm_fault *vmf) VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address, pfn, pfn << PAGE_SHIFT);
- ret = vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV)); + ret = vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV), + false);
out_unlock: mutex_unlock(&msm_obj->lock); diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c index 5c5c86d..26eebcd 100644 --- a/drivers/gpu/drm/omapdrm/omap_gem.c +++ b/drivers/gpu/drm/omapdrm/omap_gem.c @@ -393,7 +393,8 @@ static int fault_1d(struct drm_gem_object *obj, VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address, pfn, pfn << PAGE_SHIFT);
- return vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV)); + return vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV), + false); }
/* Special handling for the case of faulting in 2d tiled buffers */ @@ -486,7 +487,8 @@ static int fault_2d(struct drm_gem_object *obj, pfn, pfn << PAGE_SHIFT);
for (i = n; i > 0; i--) { - vm_insert_mixed(vma, vaddr, __pfn_to_pfn_t(pfn, PFN_DEV)); + vm_insert_mixed(vma, vaddr, __pfn_to_pfn_t(pfn, PFN_DEV), + false); pfn += priv->usergart[fmt].stride_pfn; vaddr += PAGE_SIZE * m; } diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index b442d12..e85bfa7 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -248,7 +248,7 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
if (vma->vm_flags & VM_MIXEDMAP) ret = vm_insert_mixed(&cvma, address, - __pfn_to_pfn_t(pfn, PFN_DEV)); + __pfn_to_pfn_t(pfn, PFN_DEV), false); else ret = vm_insert_pfn(&cvma, address, pfn);
diff --git a/fs/dax.c b/fs/dax.c index 306c2b6..c844a51 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -899,7 +899,7 @@ static int dax_insert_mapping(struct address_space *mapping, *entryp = ret;
trace_dax_insert_mapping(mapping->host, vmf, ret); - return vm_insert_mixed(vma, vaddr, pfn); + return vm_insert_mixed(vma, vaddr, pfn, false); }
/** diff --git a/include/linux/mm.h b/include/linux/mm.h index 46b9ac5..3eabc40 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2292,7 +2292,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn, pgprot_t pgprot); int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, - pfn_t pfn); + pfn_t pfn, bool mkwrite); int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);
diff --git a/mm/memory.c b/mm/memory.c index 0e517be..d351911 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1646,7 +1646,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, EXPORT_SYMBOL(vm_insert_page);
static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, - pfn_t pfn, pgprot_t prot) + pfn_t pfn, pgprot_t prot, bool mkwrite) { struct mm_struct *mm = vma->vm_mm; int retval; @@ -1658,14 +1658,28 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, if (!pte) goto out; retval = -EBUSY; - if (!pte_none(*pte)) - goto out_unlock; + if (!pte_none(*pte)) { + if (mkwrite) { + if (WARN_ON_ONCE(pte_pfn(*pte) != pfn_t_to_pfn(pfn))) + goto out_unlock; + entry = *pte; + goto out_mkwrite; + } else + goto out_unlock; + }
/* Ok, finally just insert the thing.. */ if (pfn_t_devmap(pfn)) entry = pte_mkdevmap(pfn_t_pte(pfn, prot)); else entry = pte_mkspecial(pfn_t_pte(pfn, prot)); + +out_mkwrite: + if (mkwrite) { + entry = pte_mkyoung(entry); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + } + set_pte_at(mm, addr, pte, entry); update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
@@ -1736,14 +1750,15 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
- ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot); + ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot, + false);
return ret; } EXPORT_SYMBOL(vm_insert_pfn_prot);
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, - pfn_t pfn) + pfn_t pfn, bool mkwrite) { pgprot_t pgprot = vma->vm_page_prot;
@@ -1772,7 +1787,7 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, page = pfn_to_page(pfn_t_to_pfn(pfn)); return insert_page(vma, addr, page, pgprot); } - return insert_pfn(vma, addr, pfn, pgprot); + return insert_pfn(vma, addr, pfn, pgprot, mkwrite); } EXPORT_SYMBOL(vm_insert_mixed);