Re: [PATCH v2 05/12] btrfs: add btrfs_try_lock_ordered_range

[Stefan Roesch <shr@fb.com>]

On 9/8/22 3:18 AM, Filipe Manana wrote:
> > 
> On Thu, Sep 8, 2022 at 1:26 AM Stefan Roesch <shr@fb.com> wrote:
>>
>> From: Josef Bacik <josef@toxicpanda.com>
>>
>> For IOCB_NOWAIT we're going to want to use try lock on the extent lock,
>> and simply bail if there's an ordered extent in the range because the
>> only choice there is to wait for the ordered extent to complete.
>>
>> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>> Signed-off-by: Stefan Roesch <shr@fb.com>
>> ---
>>  fs/btrfs/ordered-data.c | 28 ++++++++++++++++++++++++++++
>>  fs/btrfs/ordered-data.h |  1 +
>>  2 files changed, 29 insertions(+)
>>
>> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
>> index 1952ac85222c..3cdfdcedb088 100644
>> --- a/fs/btrfs/ordered-data.c
>> +++ b/fs/btrfs/ordered-data.c
>> @@ -1041,6 +1041,34 @@ void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
>>         }
>>  }
>>
>> +/*
>> + * btrfs_try_lock_ordered_range - lock the passed range and ensure all pending
>> + * ordered extents in it are run to completion in nowait mode.
>> + *
>> + * @inode:        Inode whose ordered tree is to be searched
>> + * @start:        Beginning of range to flush
>> + * @end:          Last byte of range to lock
>> + *
>> + * This function returns 1 if btrfs_lock_ordered_range does not return any
>> + * extents, otherwise 0.
> 
> Why not a bool, true/false? That's all that is needed, and it's clear.
> 
> Thanks.
>

The next version of the patch series will return bool instead of int.
 
>> + */
>> +int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end)
>> +{
>> +       struct btrfs_ordered_extent *ordered;
>> +
>> +       if (!try_lock_extent(&inode->io_tree, start, end))
>> +               return 0;
>> +
>> +       ordered = btrfs_lookup_ordered_range(inode, start, end - start + 1);
>> +       if (!ordered)
>> +               return 1;
>> +
>> +       btrfs_put_ordered_extent(ordered);
>> +       unlock_extent(&inode->io_tree, start, end);
>> +       return 0;
>> +}
>> +
>> +
>>  static int clone_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pos,
>>                                 u64 len)
>>  {
>> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
>> index 87792f85e2c4..ec27ebf0af4b 100644
>> --- a/fs/btrfs/ordered-data.h
>> +++ b/fs/btrfs/ordered-data.h
>> @@ -218,6 +218,7 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr,
>>  void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
>>                                         u64 end,
>>                                         struct extent_state **cached_state);
>> +int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end);
>>  int btrfs_split_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pre,
>>                                u64 post);
>>  int __init ordered_data_init(void);
>> --
>> 2.30.2
>>