f2fs: fix to avoid deadloop if data_flush is on
As Hagbard Celine reported:
[ 615.697824] INFO: task kworker/u16:5:344 blocked for more than 120 seconds.
[ 615.697825] Not tainted 5.0.15-gentoo-f2fslog #4
[ 615.697826] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 615.697827] kworker/u16:5 D 0 344 2 0x80000000
[ 615.697831] Workqueue: writeback wb_workfn (flush-259:0)
[ 615.697832] Call Trace:
[ 615.697836] ? __schedule+0x2c5/0x8b0
[ 615.697839] schedule+0x32/0x80
[ 615.697841] schedule_preempt_disabled+0x14/0x20
[ 615.697842] __mutex_lock.isra.8+0x2ba/0x4d0
[ 615.697845] ? log_store+0xf5/0x260
[ 615.697848] f2fs_write_data_pages+0x133/0x320
[ 615.697851] ? trace_hardirqs_on+0x2c/0xe0
[ 615.697854] do_writepages+0x41/0xd0
[ 615.697857] __filemap_fdatawrite_range+0x81/0xb0
[ 615.697859] f2fs_sync_dirty_inodes+0x1dd/0x200
[ 615.697861] f2fs_balance_fs_bg+0x2a7/0x2c0
[ 615.697863] ? up_read+0x5/0x20
[ 615.697865] ? f2fs_do_write_data_page+0x2cb/0x940
[ 615.697867] f2fs_balance_fs+0xe5/0x2c0
[ 615.697869] __write_data_page+0x1c8/0x6e0
[ 615.697873] f2fs_write_cache_pages+0x1e0/0x450
[ 615.697878] f2fs_write_data_pages+0x14b/0x320
[ 615.697880] ? trace_hardirqs_on+0x2c/0xe0
[ 615.697883] do_writepages+0x41/0xd0
[ 615.697885] __filemap_fdatawrite_range+0x81/0xb0
[ 615.697887] f2fs_sync_dirty_inodes+0x1dd/0x200
[ 615.697889] f2fs_balance_fs_bg+0x2a7/0x2c0
[ 615.697891] f2fs_write_node_pages+0x51/0x220
[ 615.697894] do_writepages+0x41/0xd0
[ 615.697897] __writeback_single_inode+0x3d/0x3d0
[ 615.697899] writeback_sb_inodes+0x1e8/0x410
[ 615.697902] __writeback_inodes_wb+0x5d/0xb0
[ 615.697904] wb_writeback+0x28f/0x340
[ 615.697906] ? cpumask_next+0x16/0x20
[ 615.697908] wb_workfn+0x33e/0x420
[ 615.697911] process_one_work+0x1a1/0x3d0
[ 615.697913] worker_thread+0x30/0x380
[ 615.697915] ? process_one_work+0x3d0/0x3d0
[ 615.697916] kthread+0x116/0x130
[ 615.697918] ? kthread_create_worker_on_cpu+0x70/0x70
[ 615.697921] ret_from_fork+0x3a/0x50
There is still deadloop in below condition:
d A
- do_writepages
- f2fs_write_node_pages
- f2fs_balance_fs_bg
- f2fs_sync_dirty_inodes
- f2fs_write_cache_pages
- mutex_lock(&sbi->writepages) -- lock once
- __write_data_page
- f2fs_balance_fs_bg
- f2fs_sync_dirty_inodes
- f2fs_write_data_pages
- mutex_lock(&sbi->writepages) -- lock again
Thread A Thread B
- do_writepages
- f2fs_write_node_pages
- f2fs_balance_fs_bg
- f2fs_sync_dirty_inodes
- .cp_task = current
- f2fs_sync_dirty_inodes
- .cp_task = current
- filemap_fdatawrite
- .cp_task = NULL
- filemap_fdatawrite
- f2fs_write_cache_pages
- enter f2fs_balance_fs_bg since .cp_task is NULL
- .cp_task = NULL
Change as below to avoid this:
- add condition to avoid holding .writepages mutex lock in path
of data flush
- introduce mutex lock sbi.flush_lock to exclude concurrent data
flush in background.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 90d1f04..adcdfa3 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -546,9 +546,13 @@
if (test_opt(sbi, DATA_FLUSH)) {
struct blk_plug plug;
+ mutex_lock(&sbi->flush_lock);
+
blk_start_plug(&plug);
f2fs_sync_dirty_inodes(sbi, FILE_INODE);
blk_finish_plug(&plug);
+
+ mutex_unlock(&sbi->flush_lock);
}
f2fs_sync_fs(sbi->sb, true);
stat_inc_bg_cp_count(sbi->stat_info);