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-rw-r--r--mm/filemap.c49
1 files changed, 28 insertions, 21 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 5020b280a771..000a220e2a41 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -906,8 +906,8 @@ EXPORT_SYMBOL(page_cache_prev_hole);
* Looks up the page cache slot at @mapping & @offset. If there is a
* page cache page, it is returned with an increased refcount.
*
- * If the slot holds a shadow entry of a previously evicted page, it
- * is returned.
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
*
* Otherwise, %NULL is returned.
*/
@@ -928,9 +928,9 @@ repeat:
if (radix_tree_deref_retry(page))
goto repeat;
/*
- * Otherwise, shmem/tmpfs must be storing a swap entry
- * here as an exceptional entry: so return it without
- * attempting to raise page count.
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Return
+ * it without attempting to raise page count.
*/
goto out;
}
@@ -983,8 +983,8 @@ EXPORT_SYMBOL(find_get_page);
* page cache page, it is returned locked and with an increased
* refcount.
*
- * If the slot holds a shadow entry of a previously evicted page, it
- * is returned.
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
*
* Otherwise, %NULL is returned.
*
@@ -1099,8 +1099,8 @@ EXPORT_SYMBOL(find_or_create_page);
* with ascending indexes. There may be holes in the indices due to
* not-present pages.
*
- * Any shadow entries of evicted pages are included in the returned
- * array.
+ * Any shadow entries of evicted pages, or swap entries from
+ * shmem/tmpfs, are included in the returned array.
*
* find_get_entries() returns the number of pages and shadow entries
* which were found.
@@ -1128,9 +1128,9 @@ repeat:
if (radix_tree_deref_retry(page))
goto restart;
/*
- * Otherwise, we must be storing a swap entry
- * here as an exceptional entry: so return it
- * without attempting to raise page count.
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Return
+ * it without attempting to raise page count.
*/
goto export;
}
@@ -1198,9 +1198,9 @@ repeat:
goto restart;
}
/*
- * Otherwise, shmem/tmpfs must be storing a swap entry
- * here as an exceptional entry: so skip over it -
- * we only reach this from invalidate_mapping_pages().
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Skip
+ * over it.
*/
continue;
}
@@ -1265,9 +1265,9 @@ repeat:
goto restart;
}
/*
- * Otherwise, shmem/tmpfs must be storing a swap entry
- * here as an exceptional entry: so stop looking for
- * contiguous pages.
+ * A shadow entry of a recently evicted page,
+ * or a swap entry from shmem/tmpfs. Stop
+ * looking for contiguous pages.
*/
break;
}
@@ -1341,10 +1341,17 @@ repeat:
goto restart;
}
/*
- * This function is never used on a shmem/tmpfs
- * mapping, so a swap entry won't be found here.
+ * A shadow entry of a recently evicted page.
+ *
+ * Those entries should never be tagged, but
+ * this tree walk is lockless and the tags are
+ * looked up in bulk, one radix tree node at a
+ * time, so there is a sizable window for page
+ * reclaim to evict a page we saw tagged.
+ *
+ * Skip over it.
*/
- BUG();
+ continue;
}
if (!page_cache_get_speculative(page))