linux-kernel - [PATCH 4.18 159/228] filesystem-dax: Fix use of zero page

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Message-Id: <20181002132509.643706157@linuxfoundation.org>
Date:   Tue,  2 Oct 2018 06:24:16 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 4.18 159/228] filesystem-dax: Fix use of zero page

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Wilcox <willy@...radead.org>

commit b90ca5cc32f59bb214847c6855959702f00c6801 upstream.

Use my_zero_pfn instead of ZERO_PAGE(), and pass the vaddr to it instead
of zero so it works on MIPS and s390 who reference the vaddr to select a
zero page.

Cc: <stable@...r.kernel.org>
Fixes: 91d25ba8a6b0 ("dax: use common 4k zero page for dax mmap reads")
Signed-off-by: Matthew Wilcox <willy@...radead.org>
Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/dax.c |   13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1007,21 +1007,12 @@ static vm_fault_t dax_load_hole(struct a
 {
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
-	vm_fault_t ret = VM_FAULT_NOPAGE;
-	struct page *zero_page;
-	pfn_t pfn;
+	pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
+	vm_fault_t ret;
 
-	zero_page = ZERO_PAGE(0);
-	if (unlikely(!zero_page)) {
-		ret = VM_FAULT_OOM;
-		goto out;
-	}
-
-	pfn = page_to_pfn_t(zero_page);
 	dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE,
 			false);
 	ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
-out:
 	trace_dax_load_hole(inode, vmf, ret);
 	return ret;
 }