On 4/12/19 9:04 AM, Thomas Hellstrom wrote:
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 <a...@linux-foundation.org>
Cc: Matthew Wilcox <wi...@infradead.org>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@surriel.com>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Michal Hocko <mho...@suse.com>
Cc: Huang Ying <ying.hu...@intel.com>
Cc: Souptick Joarder <jrdr.li...@gmail.com>
Cc: "Jérôme Glisse" <jgli...@redhat.com>
Cc: linux...@kvack.org
Cc: linux-ker...@vger.kernel.org
Signed-off-by: Thomas Hellstrom <thellst...@vmware.com>
Reviewed-by: Ralph Campbell <rcampb...@nvidia.com>
---
mm/memory.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index e11ca9dd823f..a95b4a3b1ae2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2144,7 +2144,7 @@ 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_RETRY | VM_FAULT_NOPAGE)))
A very minor nit, for consistency elsewhere in mm/memory.c,
could you make this be:
(VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)
return ret;
if (unlikely(!(ret & VM_FAULT_LOCKED))) {
lock_page(page);
@@ -2419,7 +2419,7 @@ 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_RETRY | VM_FAULT_NOPAGE))
return ret;
return finish_mkwrite_fault(vmf);
}
@@ -2440,7 +2440,8 @@ 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_RETRY |
+ VM_FAULT_NOPAGE)))) {
put_page(vmf->page);
return tmp;
}
@@ -3494,7 +3495,8 @@ 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_RETRY |
+ VM_FAULT_NOPAGE)))) {
put_page(vmf->page);
return tmp;
}
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