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authorChao Yu <yuchao0@huawei.com>2017-08-31 18:56:05 +0800
committerJaegeuk Kim <jaegeuk@kernel.org>2017-09-05 10:50:22 -0700
commitedd748e6c8e824a8281f8a8450f12c4a95ec61ee (patch)
tree69d2f53faab82737599b1c93534721c716f214ff /fs
parent025d63a486aad611b20fa39184fc86e4b76d260e (diff)
downloadop-kernel-dev-edd748e6c8e824a8281f8a8450f12c4a95ec61ee.zip
op-kernel-dev-edd748e6c8e824a8281f8a8450f12c4a95ec61ee.tar.gz
f2fs: avoid race in between atomic_read & atomic_inc
Previously, we will miss merging flush command during fsync due to below race condition: Thread A Thread B Thread C - f2fs_issue_flush - atomic_read(&issing_flush) - f2fs_issue_flush - atomic_read(&issing_flush) - f2fs_issue_flush - atomic_read(&issing_flush) - atomic_inc(&issing_flush) - atomic_inc(&issing_flush) - atomic_inc(&issing_flush) - submit_flush_wait - submit_flush_wait - submit_flush_wait It needs to use atomic_inc_return instead to avoid such race. Signed-off-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/f2fs/segment.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index d6c3f45..1215ca1 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -536,8 +536,7 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi)
return ret;
}
- if (!atomic_read(&fcc->issing_flush)) {
- atomic_inc(&fcc->issing_flush);
+ if (atomic_inc_return(&fcc->issing_flush) == 1) {
ret = submit_flush_wait(sbi);
atomic_dec(&fcc->issing_flush);
@@ -547,7 +546,6 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi)
init_completion(&cmd.wait);
- atomic_inc(&fcc->issing_flush);
llist_add(&cmd.llnode, &fcc->issue_list);
/* update issue_list before we wake up issue_flush thread */
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