Another bugfix from the XArray work; please queue for merge.

>From 4a53cab1968d2a1022f35d00b29519970ef624e9 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <[email protected]>
Date: Thu, 29 Mar 2018 22:47:50 -0400
Subject: [PATCH] dax: dax_insert_mapping_entry always succeeds

It does not return an error, so we don't need to check the return value
for IS_ERR().  Indeed, it is a bug to do so; with a sufficiently large
PFN, a legitimate DAX entry may be mistaken for an error return.

Signed-off-by: Matthew Wilcox <[email protected]>
---
 fs/dax.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index f643e8fc34ee..99c5084b845c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1005,19 +1005,13 @@ static vm_fault_t dax_load_hole(struct address_space 
*mapping, void *entry,
 {
        struct inode *inode = mapping->host;
        unsigned long vaddr = vmf->address;
-       vm_fault_t ret = VM_FAULT_NOPAGE;
-       void *entry2;
+       vm_fault_t ret;
        pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
 
-       entry2 = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
+       dax_insert_mapping_entry(mapping, vmf, entry, pfn,
                        DAX_ZERO_PAGE, false);
-       if (IS_ERR(entry2)) {
-               ret = VM_FAULT_SIGBUS;
-               goto out;
-       }
 
        ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
-out:
        trace_dax_load_hole(inode, vmf, ret);
        return ret;
 }
@@ -1327,10 +1321,6 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault 
*vmf, pfn_t *pfnp,
 
                entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
                                                 0, write && !sync);
-               if (IS_ERR(entry)) {
-                       error = PTR_ERR(entry);
-                       goto error_finish_iomap;
-               }
 
                /*
                 * If we are doing synchronous page fault and inode needs fsync,
@@ -1411,8 +1401,6 @@ static vm_fault_t dax_pmd_load_hole(struct vm_fault *vmf, 
struct iomap *iomap,
        pfn = page_to_pfn_t(zero_page);
        ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
                        DAX_PMD | DAX_ZERO_PAGE, false);
-       if (IS_ERR(ret))
-               goto fallback;
 
        ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
        if (!pmd_none(*(vmf->pmd))) {
@@ -1534,8 +1522,6 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault 
*vmf, pfn_t *pfnp,
 
                entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
                                                DAX_PMD, write && !sync);
-               if (IS_ERR(entry))
-                       goto finish_iomap;
 
                /*
                 * If we are doing synchronous page fault and inode needs fsync,
-- 
2.17.0

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