On 2023/5/24 10:35, Hugh Dickins wrote:
On Mon, 22 May 2023, Qi Zheng wrote:
On 2023/5/22 12:54, Hugh Dickins wrote:
filemap_map_pages() allow pte_offset_map_lock() to fail; and remove the
pmd_devmap_trans_unstable() check from filemap_map_pmd(), which can safely
return to filemap_map_pages() and let pte_offset_map_lock() discover that.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
mm/filemap.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 28b42ee848a4..9e129ad43e0d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3408,13 +3408,6 @@ static bool filemap_map_pmd(struct vm_fault *vmf,
struct folio *folio,
if (pmd_none(*vmf->pmd))
pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
- /* See comment in handle_pte_fault() */
- if (pmd_devmap_trans_unstable(vmf->pmd)) {
- folio_unlock(folio);
- folio_put(folio);
- return true;
- }
-
return false;
}
@@ -3501,6 +3494,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
+ if (!vmf->pte) {
+ folio_unlock(folio);
+ folio_put(folio);
Missing:
ret = VM_FAULT_NOPAGE;
?
No, not missed. Here ret is 0, which leads do_read_fault() to try
__do_fault() afterwards. Whereas VM_FAULT_NOPAGE would send it back
to userspace to retry the whole fault. Either will work, but I think
the intention of VM_FAULT_NOPAGE here in filemap_map_pages() is to say
"the page you want is now inserted", which is probably not the case.
Got it. Thanks for the explanation.
Hugh
--
Thanks,
Qi
