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Commit 52427260 authored by Qu Wenruo's avatar Qu Wenruo Committed by Filipe Manana
Browse files

btrfs: Handle delalloc error correctly to avoid ordered extent hang 



[BUG]
If run_delalloc_range() returns error and there is already some ordered
extents created, btrfs will be hanged with the following backtrace:

Call Trace:
 __schedule+0x2d4/0xae0
 schedule+0x3d/0x90
 btrfs_start_ordered_extent+0x160/0x200 [btrfs]
 ? wake_atomic_t_function+0x60/0x60
 btrfs_run_ordered_extent_work+0x25/0x40 [btrfs]
 btrfs_scrubparity_helper+0x1c1/0x620 [btrfs]
 btrfs_flush_delalloc_helper+0xe/0x10 [btrfs]
 process_one_work+0x2af/0x720
 ? process_one_work+0x22b/0x720
 worker_thread+0x4b/0x4f0
 kthread+0x10f/0x150
 ? process_one_work+0x720/0x720
 ? kthread_create_on_node+0x40/0x40
 ret_from_fork+0x2e/0x40

[CAUSE]

|<------------------ delalloc range --------------------------->|
| OE 1 | OE 2 | ... | OE n |
|<>|                       |<---------- cleanup range --------->|
 ||
 \_=> First page handled by end_extent_writepage() in __extent_writepage()

The problem is caused by error handler of run_delalloc_range(), which
doesn't handle any created ordered extents, leaving them waiting on
btrfs_finish_ordered_io() to finish.

However after run_delalloc_range() returns error, __extent_writepage()
won't submit bio, so btrfs_writepage_end_io_hook() won't be triggered
except the first page, and btrfs_finish_ordered_io() won't be triggered
for created ordered extents either.

So OE 2~n will hang forever, and if OE 1 is larger than one page, it
will also hang.

[FIX]
Introduce btrfs_cleanup_ordered_extents() function to cleanup created
ordered extents and finish them manually.

The function is based on existing
btrfs_endio_direct_write_update_ordered() function, and modify it to
act just like btrfs_writepage_endio_hook() but handles specified range
other than one page.

After fix, delalloc error will be handled like:

|<------------------ delalloc range --------------------------->|
| OE 1 | OE 2 | ... | OE n |
|<>|<--------  ----------->|<------ old error handler --------->|
 ||          ||
 ||          \_=> Cleaned up by cleanup_ordered_extents()
 \_=> First page handled by end_extent_writepage() in __extent_writepage()

Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
parent 4dbd80fb

fs/btrfs/inode.c

+48 −15
Original line number Diff line number Diff line
@@ -115,6 +115,31 @@ static struct extent_map *create_io_em(struct inode *inode, u64 start, u64 len, 
				       u64 ram_bytes, int compress_type,

				       int type);



static void __endio_write_update_ordered(struct inode *inode,

					 const u64 offset, const u64 bytes,

					 const bool uptodate);



/*

 * Cleanup all submitted ordered extents in specified range to handle errors

 * from the fill_dellaloc() callback.

 *

 * NOTE: caller must ensure that when an error happens, it can not call

 * extent_clear_unlock_delalloc() to clear both the bits EXTENT_DO_ACCOUNTING

 * and EXTENT_DELALLOC simultaneously, because that causes the reserved metadata

 * to be released, which we want to happen only when finishing the ordered

 * extent (btrfs_finish_ordered_io()). Also note that the caller of the

 * fill_delalloc() callback already does proper cleanup for the first page of

 * the range, that is, it invokes the callback writepage_end_io_hook() for the

 * range of the first page.

 */

static inline void btrfs_cleanup_ordered_extents(struct inode *inode,

						 const u64 offset,

						 const u64 bytes)

{

	return __endio_write_update_ordered(inode, offset + PAGE_SIZE,

					    bytes - PAGE_SIZE, false);

}



static int btrfs_dirty_inode(struct inode *inode);



#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
@@ -1536,6 +1561,8 @@ static int run_delalloc_range(struct inode *inode, struct page *locked_page, 
		ret = cow_file_range_async(inode, locked_page, start, end,

					   page_started, nr_written);

	}

	if (ret)

		btrfs_cleanup_ordered_extents(inode, start, end - start + 1);

	return ret;

}
@@ -8154,17 +8181,26 @@ static void btrfs_endio_direct_read(struct bio *bio) 
	bio_put(bio);

}



static void btrfs_endio_direct_write_update_ordered(struct inode *inode,

						    const u64 offset,

						    const u64 bytes,

						    const int uptodate)

static void __endio_write_update_ordered(struct inode *inode,

					 const u64 offset, const u64 bytes,

					 const bool uptodate)

{

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	struct btrfs_ordered_extent *ordered = NULL;

	struct btrfs_workqueue *wq;

	btrfs_work_func_t func;

	u64 ordered_offset = offset;

	u64 ordered_bytes = bytes;

	int ret;



	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {

		wq = fs_info->endio_freespace_worker;

		func = btrfs_freespace_write_helper;

	} else {

		wq = fs_info->endio_write_workers;

		func = btrfs_endio_write_helper;

	}



again:

	ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,

						   &ordered_offset,
@@ -8173,9 +8209,8 @@ static void btrfs_endio_direct_write_update_ordered(struct inode *inode, 
	if (!ret)

		goto out_test;



	btrfs_init_work(&ordered->work, btrfs_endio_write_helper,

			finish_ordered_fn, NULL, NULL);

	btrfs_queue_work(fs_info->endio_write_workers, &ordered->work);

	btrfs_init_work(&ordered->work, func, finish_ordered_fn, NULL, NULL);

	btrfs_queue_work(wq, &ordered->work);

out_test:

	/*

	 * our bio might span multiple ordered extents.  If we haven't
@@ -8193,10 +8228,8 @@ static void btrfs_endio_direct_write(struct bio *bio) 
	struct btrfs_dio_private *dip = bio->bi_private;

	struct bio *dio_bio = dip->dio_bio;



	btrfs_endio_direct_write_update_ordered(dip->inode,

						dip->logical_offset,

						dip->bytes,

						!bio->bi_error);

	__endio_write_update_ordered(dip->inode, dip->logical_offset,

				     dip->bytes, !bio->bi_error);



	kfree(dip);
@@ -8557,10 +8590,10 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode, 
		io_bio = NULL;

	} else {

		if (write)

			btrfs_endio_direct_write_update_ordered(inode,

			__endio_write_update_ordered(inode,

						file_offset,

						dio_bio->bi_iter.bi_size,

						0);

						false);

		else

			unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,

			      file_offset + dio_bio->bi_iter.bi_size - 1);
@@ -8695,11 +8728,11 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 
			 */

			if (dio_data.unsubmitted_oe_range_start <

			    dio_data.unsubmitted_oe_range_end)

				btrfs_endio_direct_write_update_ordered(inode,

				__endio_write_update_ordered(inode,

					dio_data.unsubmitted_oe_range_start,

					dio_data.unsubmitted_oe_range_end -

					dio_data.unsubmitted_oe_range_start,

					0);

					false);

		} else if (ret >= 0 && (size_t)ret < count)

			btrfs_delalloc_release_space(inode, offset,

						     count - (size_t)ret);