This is preparation for dropping the mmap_sem in page_mkwrite. We need to know if we used our cached page so we can be sure it is the page we already did the page_mkwrite stuff on so we don't have to redo all of that work.
Signed-off-by: Josef Bacik <jo...@toxicpanda.com> --- include/linux/mm.h | 6 +++++- mm/filemap.c | 5 ++++- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 724514be03b2..10a0118f5485 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -318,6 +318,9 @@ extern pgprot_t protection_map[16]; #define FAULT_FLAG_USER 0x40 /* The fault originated in userspace */ #define FAULT_FLAG_REMOTE 0x80 /* faulting for non current tsk/mm */ #define FAULT_FLAG_INSTRUCTION 0x100 /* The fault was during an instruction fetch */ +#define FAULT_FLAG_USED_CACHED 0x200 /* Our vmf->page was from a previous + * loop through the fault handler. + */ #define FAULT_FLAG_TRACE \ { FAULT_FLAG_WRITE, "WRITE" }, \ @@ -328,7 +331,8 @@ extern pgprot_t protection_map[16]; { FAULT_FLAG_TRIED, "TRIED" }, \ { FAULT_FLAG_USER, "USER" }, \ { FAULT_FLAG_REMOTE, "REMOTE" }, \ - { FAULT_FLAG_INSTRUCTION, "INSTRUCTION" } + { FAULT_FLAG_INSTRUCTION, "INSTRUCTION" }, \ + { FAULT_FLAG_USED_CACHED, "USED_CACHED" } /* * vm_fault is filled by the the pagefault handler and passed to the vma's diff --git a/mm/filemap.c b/mm/filemap.c index 49b35293fa95..75a8b252814a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2556,6 +2556,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) if (cached_page->mapping == mapping && cached_page->index == offset) { page = cached_page; + vmf->flags |= FAULT_FLAG_USED_CACHED; goto have_cached_page; } unlock_page(cached_page); @@ -2618,8 +2619,10 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) * We have a locked page in the page cache, now we need to check * that it's up-to-date. If not, it is going to be due to an error. */ - if (unlikely(!PageUptodate(page))) + if (unlikely(!PageUptodate(page))) { + vmf->flags &= ~(FAULT_FLAG_USED_CACHED); goto page_not_uptodate; + } /* * Found the page and have a reference on it. -- 2.14.3