mm/debug: switch dump_page to get_kernel_nofault

This is simpler to use than copy_from_kernel_nofault().  Also make some of
the related error messages less verbose.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: William Kucharski <william.kucharski@oracle.com>
Link: http://lkml.kernel.org/r/20200709202117.7216-5-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/debug.c b/mm/debug.c
index 27837c18027caf957e0c63f7499644a78f630da7..4c62ee5f0ae60dc64a340414fe237b638c8dfb07 100644 (file)
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -115,54 +115,50 @@ void __dump_page(struct page *page, const char *reason)
        else if (PageAnon(page))
                type = "anon ";
        else if (mapping) {
-               const struct inode *host;
+               struct inode *host;
                const struct address_space_operations *a_ops;
-               const struct hlist_node *dentry_first;
-               const struct dentry *dentry_ptr;
+               struct hlist_node *dentry_first;
+               struct dentry *dentry_ptr;
                struct dentry dentry;
 
                /*
                 * mapping can be invalid pointer and we don't want to crash
                 * accessing it, so probe everything depending on it carefully
                 */
-               if (copy_from_kernel_nofault(&host, &mapping->host,
-                                       sizeof(struct inode *)) ||
-                   copy_from_kernel_nofault(&a_ops, &mapping->a_ops,
-                               sizeof(struct address_space_operations *))) {
-                       pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
+               if (get_kernel_nofault(host, &mapping->host) ||
+                   get_kernel_nofault(a_ops, &mapping->a_ops)) {
+                       pr_warn("failed to read mapping contents, not a valid kernel address?\n");
                        goto out_mapping;
                }
 
                if (!host) {
-                       pr_warn("mapping->a_ops:%ps\n", a_ops);
+                       pr_warn("aops:%ps\n", a_ops);
                        goto out_mapping;
                }
 
-               if (copy_from_kernel_nofault(&dentry_first,
-                       &host->i_dentry.first, sizeof(struct hlist_node *))) {
-                       pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
-                               a_ops, host);
+               if (get_kernel_nofault(dentry_first, &host->i_dentry.first)) {
+                       pr_warn("aops:%ps with invalid host inode %px\n",
+                                       a_ops, host);
                        goto out_mapping;
                }
 
                if (!dentry_first) {
-                       pr_warn("mapping->a_ops:%ps\n", a_ops);
+                       pr_warn("aops:%ps\n", a_ops);
                        goto out_mapping;
                }
 
                dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
-               if (copy_from_kernel_nofault(&dentry, dentry_ptr,
-                                                       sizeof(struct dentry))) {
-                       pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
-                               a_ops, dentry_ptr);
+               if (get_kernel_nofault(dentry, dentry_ptr)) {
+                       pr_warn("aops:%ps with invalid dentry %px\n", a_ops,
+                                       dentry_ptr);
                } else {
                        /*
                         * if dentry is corrupted, the %pd handler may still
                         * crash, but it's unlikely that we reach here with a
                         * corrupted struct page
                         */
-                       pr_warn("mapping->aops:%ps dentry name:\"%pd\"\n",
-                                                               a_ops, &dentry);
+                       pr_warn("aops:%ps dentry name:\"%pd\"\n", a_ops,
+                                       &dentry);
                }
        }
 out_mapping: