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

Stefan Roesch
2022-09-08T18:39:11Z

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
>>