There is potential hangtask happened during swapfile's writeback:
- loop_kthread_worker_fn - do_checkpoint
- kthread_worker_fn
- loop_queue_work
- lo_rw_aio
- f2fs_file_write_iter
- f2fs_preallocate_blocks
- f2fs_map_blocks
- down_write
- down_read
- rwsem_down_read_slowpath
- schedule
One cause is f2fs_preallocate_blocks() will always be called no matter
the physical block addresses are allocated or not.
This patch tries to check whether block addresses are all allocated with
i_size and i_blocks of inode, it's rough because blocks can be allocated
beyond i_size, however, we can afford skipping block preallocation in this
condition since it's not necessary to do preallocation all the time.
Signed-off-by: Chao Yu <[email protected]>
---
v2:
- check overwrite case with i_size and i_blocks roughly.
fs/f2fs/file.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index cfdc41f87f5d..09565d10611d 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4390,6 +4390,16 @@ static int f2fs_preallocate_blocks(struct kiocb *iocb,
struct iov_iter *iter,
int flag;
int ret;
+ /*
+ * It tries to check whether block addresses are all allocated,
+ * it's rough because blocks can be allocated beyond i_size,
+ * however, we can afford skipping block preallocation since
+ * it's not necessary all the time.
+ */
+ if (F2FS_BLK_ALIGN(i_size_read(inode)) ==
+ SECTOR_TO_BLOCK(inode->i_blocks))
+ return 0;
+
/* If it will be an out-of-place direct write, don't bother. */
if (dio && f2fs_lfs_mode(sbi))
return 0;
--
2.32.0
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