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

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

[ Upstream commit d2ceb7e57086750ea6198a31fd942d98099a0786 ]

If nfs_page_async_flush() removes the page from the mapping, then we can't
use page_file_mapping() on it as nfs_updatepate() is wont to do when
receiving an error.  Instead, push the mapping to the stack before the page
is possibly truncated.

Fixes: 8fc75bed96bb ("NFS: Fix up return value on fatal errors in 
nfs_page_async_flush()")
Signed-off-by: Benjamin Coddington <bcodd...@redhat.com>
Signed-off-by: Anna Schumaker <anna.schuma...@netapp.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 fs/nfs/write.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index d790faff8e47..51d0b7913c04 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -238,9 +238,9 @@ out:
 }
 
 /* A writeback failed: mark the page as bad, and invalidate the page cache */
-static void nfs_set_pageerror(struct page *page)
+static void nfs_set_pageerror(struct address_space *mapping)
 {
-       nfs_zap_mapping(page_file_mapping(page)->host, page_file_mapping(page));
+       nfs_zap_mapping(mapping->host, mapping);
 }
 
 /*
@@ -994,7 +994,7 @@ static void nfs_write_completion(struct nfs_pgio_header 
*hdr)
                nfs_list_remove_request(req);
                if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) &&
                    (hdr->good_bytes < bytes)) {
-                       nfs_set_pageerror(req->wb_page);
+                       nfs_set_pageerror(page_file_mapping(req->wb_page));
                        nfs_context_set_write_error(req->wb_context, 
hdr->error);
                        goto remove_req;
                }
@@ -1330,7 +1330,8 @@ int nfs_updatepage(struct file *file, struct page *page,
                unsigned int offset, unsigned int count)
 {
        struct nfs_open_context *ctx = nfs_file_open_context(file);
-       struct inode    *inode = page_file_mapping(page)->host;
+       struct address_space *mapping = page_file_mapping(page);
+       struct inode    *inode = mapping->host;
        int             status = 0;
 
        nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
@@ -1348,7 +1349,7 @@ int nfs_updatepage(struct file *file, struct page *page,
 
        status = nfs_writepage_setup(ctx, page, offset, count);
        if (status < 0)
-               nfs_set_pageerror(page);
+               nfs_set_pageerror(mapping);
        else
                __set_page_dirty_nobuffers(page);
 out:
-- 
2.19.1



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