Re: [PATCH v2 08/12] btrfs: make lock_and_cleanup_extent_if_need nowait compatible

[Stefan Roesch <shr@fb.com>]

On 9/8/22 3:17 AM, Filipe Manana wrote:
> > 
> On Thu, Sep 8, 2022 at 1:26 AM Stefan Roesch <shr@fb.com> wrote:
>>
>> This adds the nowait parameter to lock_and_cleanup_extent_if_need(). If
>> the nowait parameter is specified we try to lock the extent in nowait
>> mode.
>>
>> Signed-off-by: Stefan Roesch <shr@fb.com>
>> ---
>>  fs/btrfs/file.c | 18 +++++++++++++++---
>>  1 file changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
>> index a154a3cec44b..4e1745e585cb 100644
>> --- a/fs/btrfs/file.c
>> +++ b/fs/btrfs/file.c
>> @@ -1440,7 +1440,7 @@ static noinline int
>>  lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
>>                                 size_t num_pages, loff_t pos,
>>                                 size_t write_bytes,
>> -                               u64 *lockstart, u64 *lockend,
>> +                               u64 *lockstart, u64 *lockend, bool nowait,
>>                                 struct extent_state **cached_state)
>>  {
>>         struct btrfs_fs_info *fs_info = inode->root->fs_info;
>> @@ -1455,8 +1455,20 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
>>         if (start_pos < inode->vfs_inode.i_size) {
>>                 struct btrfs_ordered_extent *ordered;
>>
>> -               lock_extent_bits(&inode->io_tree, start_pos, last_pos,
>> +               if (nowait) {
>> +                       if (!try_lock_extent(&inode->io_tree, start_pos, last_pos)) {
>> +                               for (i = 0; i < num_pages; i++) {
>> +                                       unlock_page(pages[i]);
>> +                                       put_page(pages[i]);
> 
> Since this is a non-local array, I'd prefer if we also set pages[i] to NULL.
> That may help prevent hard to debug bugs in the future.
> 
> Thanks.
> 
> 

I set pages[i] to null in the next version of the patch series.

>> +                               }
>> +
>> +                               return -EAGAIN;
>> +                       }
>> +               } else {
>> +                       lock_extent_bits(&inode->io_tree, start_pos, last_pos,
>>                                 cached_state);
>> +               }
>> +
>>                 ordered = btrfs_lookup_ordered_range(inode, start_pos,
>>                                                      last_pos - start_pos + 1);
>>                 if (ordered &&
>> @@ -1755,7 +1767,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
>>                 extents_locked = lock_and_cleanup_extent_if_need(
>>                                 BTRFS_I(inode), pages,
>>                                 num_pages, pos, write_bytes, &lockstart,
>> -                               &lockend, &cached_state);
>> +                               &lockend, false, &cached_state);
>>                 if (extents_locked < 0) {
>>                         if (extents_locked == -EAGAIN)
>>                                 goto again;
>> --
>> 2.30.2
>>