f2fs: fix potential deadlock on compressed quota file

generic/232 reports below deadlock:

fsstress        D    0 96980  96969 0x00084000
Call Trace:
 schedule+0x4a/0xb0
 io_schedule+0x12/0x40
 __lock_page+0x127/0x1d0
 pagecache_get_page+0x1d8/0x250
 prepare_compress_overwrite+0xe0/0x490 [f2fs]
 f2fs_prepare_compress_overwrite+0x5d/0x80 [f2fs]
 f2fs_write_begin+0x833/0xb90 [f2fs]
 f2fs_quota_write+0x145/0x1e0 [f2fs]
 write_blk+0x36/0x80 [quota_tree]
 do_insert_tree+0x2ac/0x4a0 [quota_tree]
 do_insert_tree+0x26e/0x4a0 [quota_tree]
 qtree_write_dquot+0x70/0x190 [quota_tree]
 v2_write_dquot+0x43/0x90 [quota_v2]
 dquot_acquire+0x77/0x100
 f2fs_dquot_acquire+0x2f/0x60 [f2fs]
 dqget+0x310/0x450
 dquot_transfer+0xb2/0x120
 f2fs_setattr+0x11a/0x4a0 [f2fs]
 notify_change+0x349/0x480
 chown_common+0x168/0x1c0
 do_fchownat+0xbc/0xf0
 __x64_sys_lchown+0x21/0x30
 do_syscall_64+0x5f/0x220
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

  task                        PC stack   pid father
kworker/u256:0  D    0 103444      2 0x80084000
Workqueue: writeback wb_workfn (flush-251:1)
Call Trace:
 schedule+0x4a/0xb0
 schedule_timeout+0x15e/0x2f0
 io_schedule_timeout+0x19/0x40
 congestion_wait+0x7e/0x120
 f2fs_write_multi_pages+0x12a/0x840 [f2fs]
 f2fs_write_cache_pages+0x48f/0x790 [f2fs]
 f2fs_write_data_pages+0x2db/0x330 [f2fs]
 do_writepages+0x1a/0x60
 __writeback_single_inode+0x3d/0x340
 writeback_sb_inodes+0x225/0x4a0
 wb_writeback+0xf7/0x320
 wb_workfn+0xba/0x470
 process_one_work+0x16c/0x3f0
 worker_thread+0x4c/0x440
 kthread+0xf8/0x130
 ret_from_fork+0x35/0x40

fsstress        D    0  5277   5266 0x00084000
Call Trace:
 schedule+0x4a/0xb0
 rwsem_down_write_slowpath+0x29d/0x540
 block_operations+0x105/0x360 [f2fs]
 f2fs_write_checkpoint+0x101/0x1010 [f2fs]
 f2fs_sync_fs+0xa8/0x130 [f2fs]
 f2fs_do_sync_file+0x1ad/0x890 [f2fs]
 do_fsync+0x38/0x60
 __x64_sys_fdatasync+0x13/0x20
 do_syscall_64+0x5f/0x220
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The root cause is there is potential deadlock between quota data
update and writeback.

Kworker					Thread B			Thread C
- f2fs_write_cache_pages
 - lock whole cluster	--- A
 - f2fs_write_multi_pages
  - f2fs_write_raw_pages
   - f2fs_write_single_data_page
    - f2fs_do_write_data_page
					- f2fs_setattr
					 - f2fs_lock_op	--- B
									- f2fs_write_checkpoint
									 - block_operations
									  - f2fs_lock_all --- B
					 - dquot_transfer
					  - f2fs_quota_write
					   - f2fs_prepare_compress_overwrite
					    - pagecache_get_page --- A
     - f2fs_trylock_op failed	--- B
  - congestion_wait
  - goto rewrite

To fix this issue, during quota file writeback, just redirty all pages
left in cluster rather holding pages' lock in cluster and looping retrying
lock cp_rwsem.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index f9cf75fe4a12e95919daaf4f17d6dec3cf2851ff..00fd6f904139c5e22999288920c6e9ad013f6d38 100644 (file)
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1002,6 +1002,15 @@ retry_write:
                                unlock_page(cc->rpages[i]);
                                ret = 0;
                        } else if (ret == -EAGAIN) {
+                               /*
+                                * for quota file, just redirty left pages to
+                                * avoid deadlock caused by cluster update race
+                                * from foreground operation.
+                                */
+                               if (IS_NOQUOTA(cc->inode)) {
+                                       err = 0;
+                                       goto out_err;
+                               }
                                ret = 0;
                                cond_resched();
                                congestion_wait(BLK_RW_ASYNC,
@@ -1011,16 +1020,12 @@ retry_write:
                                goto retry_write;
                        }
                        err = ret;
-                       goto out_fail;
+                       goto out_err;
                }
 
                *submitted += _submitted;
        }
        return 0;
-
-out_fail:
-       /* TODO: revoke partially updated block addresses */
-       BUG_ON(compr_blocks);
 out_err:
        for (++i; i < cc->cluster_size; i++) {
                if (!cc->rpages[i])