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-rw-r--r--mm/readahead.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index 73cb59ed5cff..3c9a8dd7c56c 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -22,6 +22,7 @@
#include <linux/mm_inline.h>
#include <linux/blk-cgroup.h>
#include <linux/fadvise.h>
+#include <linux/sched/mm.h>
#include "internal.h"
@@ -186,6 +187,18 @@ void page_cache_readahead_unbounded(struct address_space *mapping,
unsigned long i;
/*
+ * Partway through the readahead operation, we will have added
+ * locked pages to the page cache, but will not yet have submitted
+ * them for I/O. Adding another page may need to allocate memory,
+ * which can trigger memory reclaim. Telling the VM we're in
+ * the middle of a filesystem operation will cause it to not
+ * touch file-backed pages, preventing a deadlock. Most (all?)
+ * filesystems already specify __GFP_NOFS in their mapping's
+ * gfp_mask, but let's be explicit here.
+ */
+ unsigned int nofs = memalloc_nofs_save();
+
+ /*
* Preallocate as many pages as we will need.
*/
for (i = 0; i < nr_to_read; i++) {
@@ -229,6 +242,7 @@ void page_cache_readahead_unbounded(struct address_space *mapping,
* will then handle the error.
*/
read_pages(&rac, &page_pool, false);
+ memalloc_nofs_restore(nofs);
}
EXPORT_SYMBOL_GPL(page_cache_readahead_unbounded);