mm/hmm: add missing unmaps of the ptep during hmm_vma_handle_pte()

Many of the direct returns of error skipped doing the pte_unmap(). All non
zero exit paths must unmap the pte.

The pte_unmap() is split unnaturally like this because some of the error
exit paths trigger a sleep and must release the lock before sleeping.

Fixes: 992de9a8b751 ("mm/hmm: allow to mirror vma of a file on a DAX backed filesystem")
Fixes: 53f5c3f489ec ("mm/hmm: factor out pte and pmd handling to simplify hmm_vma_walk_pmd()")
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/mm/hmm.c b/mm/hmm.c
index 72e5a6d..35f8542 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -325,6 +325,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
                }
 
                /* Report error for everything else */
+               pte_unmap(ptep);
                *pfn = range->values[HMM_PFN_ERROR];
                return -EFAULT;
        } else {
@@ -339,10 +340,13 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
        if (pte_devmap(pte)) {
                hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte),
                                              hmm_vma_walk->pgmap);
-               if (unlikely(!hmm_vma_walk->pgmap))
+               if (unlikely(!hmm_vma_walk->pgmap)) {
+                       pte_unmap(ptep);
                        return -EBUSY;
+               }
        } else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
                if (!is_zero_pfn(pte_pfn(pte))) {
+                       pte_unmap(ptep);
                        *pfn = range->values[HMM_PFN_SPECIAL];
                        return -EFAULT;
                }
@@ -437,7 +441,7 @@ again:
 
                r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
                if (r) {
-                       /* hmm_vma_handle_pte() did unmap pte directory */
+                       /* hmm_vma_handle_pte() did pte_unmap() */
                        hmm_vma_walk->last = addr;
                        return r;
                }