On Sun 24-11-19 20:20:09, John Hubbard wrote: > 1. Convert from get_user_pages() to pin_user_pages(). > > 2. As required by pin_user_pages(), release these pages via > put_user_page(). In this case, do so via put_user_pages_dirty_lock(). > > That has the side effect of calling set_page_dirty_lock(), instead > of set_page_dirty(). This is probably more accurate. > > As Christoph Hellwig put it, "set_page_dirty() is only safe if we are > dealing with a file backed page where we have reference on the inode it > hangs off." [1] > > 3. Release each page in mem->hpages[] (instead of mem->hpas[]), because > that is the array that pin_longterm_pages() filled in. This is more > accurate and should be a little safer from a maintenance point of > view. Except that this breaks the code. hpages is unioned with hpas... > [1] https://lore.kernel.org/r/20190723153640.GB720@xxxxxx > > Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> > --- > arch/powerpc/mm/book3s64/iommu_api.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c > index 56cc84520577..196383e8e5a9 100644 > --- a/arch/powerpc/mm/book3s64/iommu_api.c > +++ b/arch/powerpc/mm/book3s64/iommu_api.c > @@ -103,7 +103,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua, > for (entry = 0; entry < entries; entry += chunk) { > unsigned long n = min(entries - entry, chunk); > > - ret = get_user_pages(ua + (entry << PAGE_SHIFT), n, > + ret = pin_user_pages(ua + (entry << PAGE_SHIFT), n, > FOLL_WRITE | FOLL_LONGTERM, > mem->hpages + entry, NULL); > if (ret == n) { > @@ -167,9 +167,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua, > return 0; > > free_exit: > - /* free the reference taken */ > - for (i = 0; i < pinned; i++) > - put_page(mem->hpages[i]); > + /* free the references taken */ > + put_user_pages(mem->hpages, pinned); > > vfree(mem->hpas); > kfree(mem); > @@ -212,10 +211,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem) > if (!page) > continue; > > - if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY) > - SetPageDirty(page); > + put_user_pages_dirty_lock(&mem->hpages[i], 1, > + MM_IOMMU_TABLE_GROUP_PAGE_DIRTY); And the dirtying condition is wrong here as well. Currently it is always true. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
