| Message ID | 44ebbf90-5fbb-2815-17c7-fcfe3c87d78e@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arch: allow pte_offset_map[_lock]() to fail | expand |
Hi Hugh, On 5/10/23 06:52, Hugh Dickins wrote: > To keep balance in future, remember to pte_unmap() after a successful > get_ptep(). And (we might as well) pretend that flush_cache_pages() > really needed a map there, to read the pfn before "unmapping". > > Signed-off-by: Hugh Dickins <hughd@google.com> > --- > arch/parisc/kernel/cache.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c > index 1d3b8bc8a623..b0c969b3a300 100644 > --- a/arch/parisc/kernel/cache.c > +++ b/arch/parisc/kernel/cache.c > @@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page) > offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; > addr = mpnt->vm_start + offset; > if (parisc_requires_coherency()) { > + bool needs_flush = false; > pte_t *ptep; > > ptep = get_ptep(mpnt->vm_mm, addr); > - if (ptep && pte_needs_flush(*ptep)) > + if (ptep) { > + needs_flush = pte_needs_flush(*ptep); > + pte_unmap(ptep); > + } > + if (needs_flush) > flush_user_cache_page(mpnt, addr); > } else { > /* > @@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr); > static void flush_cache_page_if_present(struct vm_area_struct *vma, > unsigned long vmaddr, unsigned long pfn) > { > - pte_t *ptep = get_ptep(vma->vm_mm, vmaddr); > + bool needs_flush = false; > + pte_t *ptep; > > /* > * The pte check is racy and sometimes the flush will trigger > * a non-access TLB miss. Hopefully, the page has already been > * flushed. > */ > - if (ptep && pte_needs_flush(*ptep)) > + ptep = get_ptep(vma->vm_mm, vmaddr); > + if (ptep) { > + needs_flush = pte_needs_flush(*ptep)) ^^^^^ One ")" too much and lacks a trailing ";" Should be: needs_flush = pte_needs_flush(*ptep); With that fixed the kernel compiles and boots sucessfully on parisc. Helge
On Sat, 13 May 2023, Helge Deller wrote: > Hi Hugh, > > On 5/10/23 06:52, Hugh Dickins wrote: > > To keep balance in future, remember to pte_unmap() after a successful > > get_ptep(). And (we might as well) pretend that flush_cache_pages() > > really needed a map there, to read the pfn before "unmapping". > > > > Signed-off-by: Hugh Dickins <hughd@google.com> > > --- > > arch/parisc/kernel/cache.c | 26 +++++++++++++++++++++----- > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c > > index 1d3b8bc8a623..b0c969b3a300 100644 > > --- a/arch/parisc/kernel/cache.c > > +++ b/arch/parisc/kernel/cache.c > > @@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page) > > offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; > > addr = mpnt->vm_start + offset; > > if (parisc_requires_coherency()) { > > + bool needs_flush = false; > > pte_t *ptep; > > > > ptep = get_ptep(mpnt->vm_mm, addr); > > - if (ptep && pte_needs_flush(*ptep)) > > + if (ptep) { > > + needs_flush = pte_needs_flush(*ptep); > > + pte_unmap(ptep); > > + } > > + if (needs_flush) > > flush_user_cache_page(mpnt, addr); > > } else { > > /* > > @@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr); > > static void flush_cache_page_if_present(struct vm_area_struct *vma, > > unsigned long vmaddr, unsigned long pfn) > > { > > - pte_t *ptep = get_ptep(vma->vm_mm, vmaddr); > > + bool needs_flush = false; > > + pte_t *ptep; > > > > /* > > * The pte check is racy and sometimes the flush will trigger > > * a non-access TLB miss. Hopefully, the page has already been > > * flushed. > > */ > > - if (ptep && pte_needs_flush(*ptep)) > > + ptep = get_ptep(vma->vm_mm, vmaddr); > > + if (ptep) { > > + needs_flush = pte_needs_flush(*ptep)) > > ^^^^^ > One ")" too much and lacks a trailing ";" > Should be: > needs_flush = pte_needs_flush(*ptep); > > With that fixed the kernel compiles and boots sucessfully on parisc. Urgh! Indeed, thanks a lot Helge: I'll fold that in. Hugh
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c index 1d3b8bc8a623..b0c969b3a300 100644 --- a/arch/parisc/kernel/cache.c +++ b/arch/parisc/kernel/cache.c @@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page) offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; addr = mpnt->vm_start + offset; if (parisc_requires_coherency()) { + bool needs_flush = false; pte_t *ptep; ptep = get_ptep(mpnt->vm_mm, addr); - if (ptep && pte_needs_flush(*ptep)) + if (ptep) { + needs_flush = pte_needs_flush(*ptep); + pte_unmap(ptep); + } + if (needs_flush) flush_user_cache_page(mpnt, addr); } else { /* @@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr); static void flush_cache_page_if_present(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long pfn) { - pte_t *ptep = get_ptep(vma->vm_mm, vmaddr); + bool needs_flush = false; + pte_t *ptep; /* * The pte check is racy and sometimes the flush will trigger * a non-access TLB miss. Hopefully, the page has already been * flushed. */ - if (ptep && pte_needs_flush(*ptep)) + ptep = get_ptep(vma->vm_mm, vmaddr); + if (ptep) { + needs_flush = pte_needs_flush(*ptep)) + pte_unmap(ptep); + } + if (needs_flush) flush_cache_page(vma, vmaddr, pfn); } @@ -634,17 +645,22 @@ static void flush_cache_pages(struct vm_area_struct *vma, unsigned long start, u pte_t *ptep; for (addr = start; addr < end; addr += PAGE_SIZE) { + bool needs_flush = false; /* * The vma can contain pages that aren't present. Although * the pte search is expensive, we need the pte to find the * page pfn and to check whether the page should be flushed. */ ptep = get_ptep(vma->vm_mm, addr); - if (ptep && pte_needs_flush(*ptep)) { + if (ptep) { + needs_flush = pte_needs_flush(*ptep); + pfn = pte_pfn(*ptep); + pte_unmap(ptep); + } + if (needs_flush) { if (parisc_requires_coherency()) { flush_user_cache_page(vma, addr); } else { - pfn = pte_pfn(*ptep); if (WARN_ON(!pfn_valid(pfn))) return; __flush_cache_page(vma, addr, PFN_PHYS(pfn));
To keep balance in future, remember to pte_unmap() after a successful get_ptep(). And (we might as well) pretend that flush_cache_pages() really needed a map there, to read the pfn before "unmapping". Signed-off-by: Hugh Dickins <hughd@google.com> --- arch/parisc/kernel/cache.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-)