Messages in this thread | | | Subject | Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty | From | Jürgen Groß <> | Date | Tue, 7 Jul 2020 13:43:12 +0200 |
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On 07.07.20 13:30, Souptick Joarder wrote: > On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß <jgross@suse.com> wrote: >> >> On 06.07.20 20:16, Souptick Joarder wrote: >>> pages need to be marked as dirty before unpinned it in >>> unlock_pages() which was oversight. This is fixed now. >>> >>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> >>> Suggested-by: John Hubbard <jhubbard@nvidia.com> >>> Cc: John Hubbard <jhubbard@nvidia.com> >>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> >>> Cc: Paul Durrant <xadimgnik@gmail.com> >>> --- >>> drivers/xen/privcmd.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c >>> index 33677ea..f6c1543 100644 >>> --- a/drivers/xen/privcmd.c >>> +++ b/drivers/xen/privcmd.c >>> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages) >>> { >>> unsigned int i; >>> >>> - for (i = 0; i < nr_pages; i++) >>> + for (i = 0; i < nr_pages; i++) { >>> + if (!PageDirty(pages[i])) >>> + set_page_dirty_lock(pages[i]); >> >> With put_page() directly following I think you should be able to use >> set_page_dirty() instead, as there is obviously a reference to the page >> existing. > > Patch [3/3] will convert above codes to use unpin_user_pages_dirty_lock() > which internally do the same check. So I thought to keep linux-stable and > linux-next code in sync. John had a similar concern [1] and later agreed to keep > this check. > > Shall I keep this check ? No ? > > [1] https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/
I wasn't referring to checking PageDirty(), but to the use of set_page_dirty_lock().
Looking at the comment just before the implementation of set_page_dirty_lock() suggests that it is fine to use set_page_dirty() instead (so not calling lock_page()).
Only the transition from get_user_pages_fast() to pin_user_pages_fast() requires to use the locked version IMO.
Juergen
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