summaryrefslogtreecommitdiff
path: root/mm/readahead.c
diff options
context:
space:
mode:
authorMatthew Wilcox (Oracle) <willy@infradead.org>2020-06-02 07:46:58 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 20:59:07 +0300
commitf2c817bed58d9be2051fad1d18e167e173c0c227 (patch)
tree445bd1c5a8a3639aa596ef6d4137ae44619a78c4 /mm/readahead.c
parent2d8163e4899dad92175eedd1c2326c875eaa74fa (diff)
downloadlinux-f2c817bed58d9be2051fad1d18e167e173c0c227.tar.xz
mm: use memalloc_nofs_save in readahead path
Ensure that memory allocations in the readahead path do not attempt to reclaim file-backed pages, which could lead to a deadlock. It is possible, though unlikely this is the root cause of a problem observed by Cong Wang. Reported-by: Cong Wang <xiyou.wangcong@gmail.com> Suggested-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Miklos Szeredi <mszeredi@redhat.com> Link: http://lkml.kernel.org/r/20200414150233.24495-16-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/readahead.c')
-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);