On Thu, Sep 09, 2021 at 02:47:50PM +0200, David Sterba wrote:
> From: Qu Wenruo <wqu@xxxxxxxx>
>
> commit 4e9655763b82a91e4c341835bb504a2b1590f984 upstream.
>
> This reverts commit f2165627319ffd33a6217275e5690b1ab5c45763.
>
> [BUG]
> It's no longer possible to create compressed inline extent after commit
> f2165627319f ("btrfs: compression: don't try to compress if we don't
> have enough pages").
>
> [CAUSE]
> For compression code, there are several possible reasons we have a range
> that needs to be compressed while it's no more than one page.
>
> - Compressed inline write
> The data is always smaller than one sector and the test lacks the
> condition to properly recognize a non-inline extent.
>
> - Compressed subpage write
> For the incoming subpage compressed write support, we require page
> alignment of the delalloc range.
> And for 64K page size, we can compress just one page into smaller
> sectors.
>
> For those reasons, the requirement for the data to be more than one page
> is not correct, and is already causing regression for compressed inline
> data writeback. The idea of skipping one page to avoid wasting CPU time
> could be revisited in the future.
>
> [FIX]
> Fix it by reverting the offending commit.
>
> Reported-by: Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/linux-btrfs/afa2742.c084f5d6.17b6b08dffc@xxxxxxxxxxxx
> Fixes: f2165627319f ("btrfs: compression: don't try to compress if we don't have enough pages")
> CC: stable@xxxxxxxxxxxxxxx # 4.4+
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> Reviewed-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> ---
> fs/btrfs/inode.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 29552d4f6845..33b8fedab6c6 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -543,7 +543,7 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
> * inode has not been flagged as nocompress. This flag can
> * change at any time if we discover bad compression ratios.
> */
> - if (nr_pages > 1 && inode_need_compress(inode, start, end)) {
> + if (inode_need_compress(inode, start, end)) {
> WARN_ON(pages);
> pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
> if (!pages) {
> --
> 2.33.0
>
All now queued up, thanks.
greg k-h
