On Fri, Sep 01, 2017 at 07:31:58PM +0800, Qu Wenruo wrote:
>
>
> On 2017年09月01日 16:59, Naohiro Aota wrote:
> > __endio_write_update_ordered() repeats the search until it reaches the end
> > of the specified range. This works well with direct IO path, because before
> > the function is called, it's ensured that there are ordered extents filling
> > whole the range. It's not the case, however, when it's called from
> > run_delalloc_range(): it is possible to have error in the midle of the loop
> > in e.g. run_delalloc_nocow(), so that there exisits the range not covered
> > by any ordered extents. By cleaning such "uncomplete" range,
> > __endio_write_update_ordered() stucks at offset where there're no ordered
> > extents.
> >
> > Since the ordered extents are created from head to tail, we can stop the
> > search if there are no offset progress.
> >
> > Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
> > Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> > Cc: <stable@xxxxxxxxxxxxxxx> # 4.12
> > ---
> > fs/btrfs/inode.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index ae4c0a1bef38..fd5934121b4b 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -8309,6 +8309,7 @@ static void __endio_write_update_ordered(struct inode *inode,
> > btrfs_work_func_t func;
> > u64 ordered_offset = offset;
> > u64 ordered_bytes = bytes;
> > + u64 last_offset;
> > int ret;
> >
> > if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
> > @@ -8320,6 +8321,7 @@ static void __endio_write_update_ordered(struct inode *inode,
> > }
> >
> > again:
> > + last_offset = ordered_offset;
> > ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
> > &ordered_offset,
> > ordered_bytes,
> > @@ -8330,6 +8332,8 @@ static void __endio_write_update_ordered(struct inode *inode,
> > btrfs_init_work(&ordered->work, func, finish_ordered_fn, NULL, NULL);
> > btrfs_queue_work(wq, &ordered->work);
> > out_test:
> > + if (ordered_offset == last_offset)
> > + return;
>
> Such check seems strange to me.
>
> For ordered_offset == last_offset case, it means
> btrfs_dec_test_ordered_pending() doesn't find any ordered extent in that
> range, so we can exit.
> This takes me a while to dig into btrfs_dec_test_first_ordered_pending().
>
> Extra comment will help here, or to modify
> btrfs_dev_test_ordered_pending() to explicitly info caller there is no
> extra pending ordered extent.
I'll update the patch with the comment based on your note, please send a
patch with the proposed code changes if you like.
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