Re: [PATCH 19/20] dax: Protect PTE modification on WP fault by radix tree entry lock
From: Ross Zwisler <hidden>
Date: 2016-10-18 19:53:32
Also in:
linux-fsdevel, nvdimm
On Tue, Sep 27, 2016 at 06:08:23PM +0200, Jan Kara wrote:
Currently PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite() has released corresponding radix tree entry lock. When we want to writeprotect PTE on cache flush, we need PTE modification to happen under radix tree entry lock to ensure consisten updates of PTE and radix
consistent
quoted hunk ↗ jump to hunk
tree (standard faults use page lock to ensure this consistency). So move update of PTE bit into dax_pfn_mkwrite(). Signed-off-by: Jan Kara <jack@suse.cz> --- fs/dax.c | 22 ++++++++++++++++------ mm/memory.c | 2 +- 2 files changed, 17 insertions(+), 7 deletions(-)diff --git a/fs/dax.c b/fs/dax.c index c6cadf8413a3..a2d3781c9f4e 100644 --- a/fs/dax.c +++ b/fs/dax.c@@ -1163,17 +1163,27 @@ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) { struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; - void *entry; + void *entry, **slot; pgoff_t index = vmf->pgoff; spin_lock_irq(&mapping->tree_lock); - entry = get_unlocked_mapping_entry(mapping, index, NULL); - if (!entry || !radix_tree_exceptional_entry(entry)) - goto out; + entry = get_unlocked_mapping_entry(mapping, index, &slot); + if (!entry || !radix_tree_exceptional_entry(entry)) { + if (entry) + put_unlocked_mapping_entry(mapping, index, entry);
I don't think you need this call to put_unlocked_mapping_entry(). If we get in here we know that 'entry' is a page cache page, in which case put_unlocked_mapping_entry() will just return without doing any work. With that nit & the spelling error above: Reviewed-by: Ross Zwisler <redacted> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>