Re: [PATCH v2] btrfs: Remove force argument from run_delalloc_nocow()

From: David Sterba <dsterba@suse.cz>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-btrfs@vger.kernel.org, dsterba@suse.cz
Subject: Re: [PATCH v2] btrfs: Remove force argument from run_delalloc_nocow()
Date: Fri, 26 Feb 2021 18:14:21 +0100	[thread overview]
Message-ID: <20210226171421.GO7604@twin.jikos.cz> (raw)
In-Reply-To: <20210225205822.mgx5ei3tzcqmlts6@fiona>

On Thu, Feb 25, 2021 at 02:58:22PM -0600, Goldwyn Rodrigues wrote:
> force_nocow can be calculated by btrfs_inode and does not need to be
> passed as an argument.
> 
> This simplifies run_delalloc_nocow() call from btrfs_run_delalloc_range()
> since the decision whether the extent is cow'd or not can be derived
> from need_force_cow(). Since BTRFS_INODE_NODATACOW and
> BTRFS_INODE_PREALLOC flags are checked in need_force_cow(), there is
> no need to check it again.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Change since v1:
>  - Kept need_force_cow() as it is

Added to misc-next, thanks.

> ---
>  fs/btrfs/inode.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 4f2f1e932751..e5dd8d7ef0c8 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -1516,7 +1516,7 @@ static int fallback_to_cow(struct btrfs_inode *inode, struct page *locked_page,
>  static noinline int run_delalloc_nocow(struct btrfs_inode *inode,
>  				       struct page *locked_page,
>  				       const u64 start, const u64 end,
> -				       int *page_started, int force,
> +				       int *page_started,
>  				       unsigned long *nr_written)
>  {
>  	struct btrfs_fs_info *fs_info = inode->root->fs_info;
> @@ -1530,6 +1530,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode,
>  	u64 ino = btrfs_ino(inode);
>  	bool nocow = false;
>  	u64 disk_bytenr = 0;
> +	bool force = inode->flags & BTRFS_INODE_NODATACOW;
>  
>  	path = btrfs_alloc_path();
>  	if (!path) {
> @@ -1891,17 +1892,12 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page
>  		struct writeback_control *wbc)
>  {
>  	int ret;
> -	int force_cow = need_force_cow(inode, start, end);
>  	const bool zoned = btrfs_is_zoned(inode->root->fs_info);
>  
> -	if (inode->flags & BTRFS_INODE_NODATACOW && !force_cow) {
> +	if (!need_force_cow(inode, start, end)) {

We may want to reverse the logic and naming so it says
'need_force_nocow', right now it's "we don't need to force COW, so let's
do NOCOW", because COW is the default and the condition should pick the
exceptional case.

>  		ASSERT(!zoned);
>  		ret = run_delalloc_nocow(inode, locked_page, start, end,
> -					 page_started, 1, nr_written);
> -	} else if (inode->flags & BTRFS_INODE_PREALLOC && !force_cow) {
> -		ASSERT(!zoned);
> -		ret = run_delalloc_nocow(inode, locked_page, start, end,
> -					 page_started, 0, nr_written);
> +					 page_started, nr_written);
>  	} else if (!inode_can_compress(inode) ||
>  		   !inode_need_compress(inode, start, end)) {
>  		if (zoned)
> -- 
> 2.30.1
> 
> 
> -- 
> Goldwyn