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

Filipe Manana
2022-09-08T10:17:59Z

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.

> + }
> +
> + 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
>