Hi Chao, Jaegeuk,
I have received an issue report that indicates that system is stuck
on IO due to f2fs checkpoint and writeback stuck waiting on each other
as explained below.
WB thread -
----------
io_schedule
wait_on_page_bit
f2fs_wait_on_page_writeback -> It is waiting for node
node page writeback whose bio is in the
plug list of CP thread below.
f2fs_update_data_blkaddr
f2fs_outplace_write_data
f2fs_do_write_data_page
__write_data_page
__f2fs_write_data_pages
f2fs_write_data_pages
do_writepages
CP thread -
-----------
__f2fs_write_data_pages -> It is for the same inode above that is under WB
(which
is waiting for node page writeback). In this context, there is nothing
to
be written as the data is already under WB.
filemap_fdatawrite
f2fs_sync_dirty_inodes -> It just loops here in f2fs_sync_dirty_inodes() until
f2fs_remove_dirty_inode() has been done by the WB
thread above.
block_operations
f2fs_write_checkpoint
The CP thread somehow has the node page bio in its plug list that cannot be
submitted
until end of block_operations() and CP thread is blocked on WB of an inode who
is again
waiting for io pending in CP plug list. Both the stacks are stuck on for each
other.
The below patch helped to solve the issue, please review and suggest if this
seems to
be okay. Since anyways we are doing cond_resched(), I thought it will be good
to flush
the plug list as well (in this issue case, it will loop for the same inode
again and again).
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index e460d90..152df48 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1071,10 +1071,12 @@ int f2fs_sync_dirty_inodes(struct f2fs_sb_info *sbi,
enum inode_type type)
iput(inode);
/* We need to give cpu to another writers. */
- if (ino == cur_ino)
+ if (ino == cur_ino) {
+ blk_flush_plug(current);
cond_resched();
- else
+ } else {
ino = cur_ino;
+ }
} else {
/*
* We should submit bio, since it exists several
Thanks,
--
--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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