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authorTejun Heo <tj@kernel.org>2017-12-12 19:38:30 +0300
committerJens Axboe <axboe@kernel.dk>2019-01-23 00:39:38 +0300
commit7fc5854f8c6efae9e7624970ab49a1eac2faefb1 (patch)
tree7c9ac9ab43c0a47dbaefd155da89c8ba7f7923db /mm/backing-dev.c
parent698cef173983b086977e633e46476e0f925ca01e (diff)
downloadlinux-7fc5854f8c6efae9e7624970ab49a1eac2faefb1.tar.xz
writeback: synchronize sync(2) against cgroup writeback membership switches
sync_inodes_sb() can race against cgwb (cgroup writeback) membership switches and fail to writeback some inodes. For example, if an inode switches to another wb while sync_inodes_sb() is in progress, the new wb might not be visible to bdi_split_work_to_wbs() at all or the inode might jump from a wb which hasn't issued writebacks yet to one which already has. This patch adds backing_dev_info->wb_switch_rwsem to synchronize cgwb switch path against sync_inodes_sb() so that sync_inodes_sb() is guaranteed to see all the target wbs and inodes can't jump wbs to escape syncing. v2: Fixed misplaced rwsem init. Spotted by Jiufei. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jiufei Xue <xuejiufei@gmail.com> Link: http://lkml.kernel.org/r/dc694ae2-f07f-61e1-7097-7c8411cee12d@gmail.com Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm/backing-dev.c')
-rw-r--r--mm/backing-dev.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 8a8bb8796c6c..72e6d0c55cfa 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -689,6 +689,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
bdi->cgwb_congested_tree = RB_ROOT;
mutex_init(&bdi->cgwb_release_mutex);
+ init_rwsem(&bdi->wb_switch_rwsem);
ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (!ret) {