Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-10-26 09:07:11
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On Wed 26-10-16 08:59:52, Lorenzo Stoakes wrote:
On Wed, Oct 26, 2016 at 12:36:09AM +0100, Lorenzo Stoakes wrote:quoted
In hva_to_pfn_slow() we are able to replace __get_user_pages_unlocked() with get_user_pages_unlocked() since we can now pass gup_flags. In async_pf_execute() we need to pass different tsk, mm arguments so get_user_pages_remote() is the sane replacement here (having added manual acquisition and release of mmap_sem.) Since we pass a NULL pages parameter the subsequent call to __get_user_pages_locked() will have previously bailed any attempt at VM_FAULT_RETRY, so we do not change this behaviour by using get_user_pages_remote() which does not invoke VM_FAULT_RETRY logic at all. Signed-off-by: Lorenzo Stoakes <redacted>Note that the use of get_user_pages_remote() in async_pf_execute() reintroduces the use of the FOLL_TOUCH flag - I don't think this is a problem as this flag was dropped by 1e987790 ("mm/gup: Introduce get_user_pages_remote()") which states 'Without protection keys, this patch should not change any behavior', so I don't think this was intentional.
Yes, I have already mentioned this in one of my previous emails. This indeed doesn't seem to be intentional -- Michal Hocko SUSE Labs -- 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>