f2fs: avoid double lock for cp_rwsem
The __f2fs_add_link is covered by cp_rwsem all the time.
This calls init_inode_metadata, which conducts some acl operations including
memory allocation with GFP_KERNEL previously.
But, under memory pressure, f2fs_write_data_page can be called, which also
grabs cp_rwsem too.
In this case, this incurs a deadlock pointed by Chao.
Thread #1 Thread #2
down_read
down_write
down_read
-> here down_read should wait forever.
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 1ccb26b..7f12d28 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -62,7 +62,7 @@
if (count == 0)
return NULL;
- acl = posix_acl_alloc(count, GFP_KERNEL);
+ acl = posix_acl_alloc(count, GFP_NOFS);
if (!acl)
return ERR_PTR(-ENOMEM);
@@ -116,7 +116,7 @@
int i;
f2fs_acl = kmalloc(sizeof(struct f2fs_acl_header) + acl->a_count *
- sizeof(struct f2fs_acl_entry), GFP_KERNEL);
+ sizeof(struct f2fs_acl_entry), GFP_NOFS);
if (!f2fs_acl)
return ERR_PTR(-ENOMEM);