mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem (c9e5f41f) · Commits · 戴 / test

Driver fault callbacks are allowed to drop the mmap_sem when expecting long hardware waits to avoid blocking other mm users. Allow the mkwrite callbacks to do the same by returning early on VM_FAULT_RETRY. In particular we want to be able to drop the mmap_sem when waiting for a reservation object lock on a GPU buffer object. These locks may be held while waiting for the GPU. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Souptick Joarder <jrdr.linux@gmail.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by:

Thomas Hellstrom <thellstrom@vmware.com> Reviewed-by:

Ralph Campbell <rcampbell@nvidia.com>

mm/memory.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -2238,7 +2238,7 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
		ret = vmf->vma->vm_ops->page_mkwrite(vmf);
		/* Restore original flags so that caller is not surprised */
		vmf->flags = old_flags;
		if (unlikely(ret & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE)))
		if (unlikely(ret & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE \| VM_FAULT_RETRY)))
		return ret;
		if (unlikely(!(ret & VM_FAULT_LOCKED))) {
		lock_page(page);
		@@ -2515,7 +2515,7 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		vmf->flags \|= FAULT_FLAG_MKWRITE;
		ret = vma->vm_ops->pfn_mkwrite(vmf);
		if (ret & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE))
		if (ret & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE \| VM_FAULT_RETRY))
		return ret;
		return finish_mkwrite_fault(vmf);
		}
		@@ -2536,7 +2536,8 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf)
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		tmp = do_page_mkwrite(vmf);
		if (unlikely(!tmp \|\| (tmp &
		(VM_FAULT_ERROR \| VM_FAULT_NOPAGE)))) {
		(VM_FAULT_ERROR \| VM_FAULT_NOPAGE \|
		VM_FAULT_RETRY)))) {
		put_page(vmf->page);
		return tmp;
		}
		@@ -3601,7 +3602,8 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
		unlock_page(vmf->page);
		tmp = do_page_mkwrite(vmf);
		if (unlikely(!tmp \|\|
		(tmp & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE)))) {
		(tmp & (VM_FAULT_ERROR \| VM_FAULT_NOPAGE \|
		VM_FAULT_RETRY)))) {
		put_page(vmf->page);
		return tmp;
		}

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