From: Thomas Hellstrom <[email protected]> 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 <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Will Deacon <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Huang Ying <[email protected]> Cc: Souptick Joarder <[email protected]> Cc: "Jérôme Glisse" <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Thomas Hellstrom <[email protected]> Reviewed-by: Ralph Campbell <[email protected]> --- mm/memory.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index ddf20bd0c317..168f546af1ad 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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; } -- 2.20.1
