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Date:   Mon, 22 Jul 2019 19:36:40 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2] f2fs: separate NOCoW and pinfile semantics
Message-ID: <20190723023640.GC60778@jaegeuk-macbookpro.roam.corp.google.com>
References: <20190719073903.9138-1-yuchao0@huawei.com>
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On 07/19, Chao Yu wrote:
> Pinning a file is heavy, because skipping pinned files make GC
> running with heavy load or no effect.

Pinned file is a part of NOCOW files, so I don't think we can simply drop it
for backward compatibility.

> 
> So that this patch propose to separate nocow and pinfile semantics:
> - NOCoW flag can only be set on regular file.
> - NOCoW file will only trigger IPU at common writeback/flush.
> - NOCow file will do OPU during GC.
> 
> For the demand of 1) avoid fragment of file's physical block and
> 2) userspace don't care about file's specific physical address,
> tagging file as NOCoW will be cheaper than pinned one.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> v2:
> - rebase code to fix compile error.
>  fs/f2fs/data.c |  3 ++-
>  fs/f2fs/f2fs.h |  1 +
>  fs/f2fs/file.c | 22 +++++++++++++++++++---
>  3 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index a2a28bb269bf..15fb8954c363 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1884,7 +1884,8 @@ static inline bool check_inplace_update_policy(struct inode *inode,
>  
>  bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
>  {
> -	if (f2fs_is_pinned_file(inode))
> +	if (f2fs_is_pinned_file(inode) ||
> +			F2FS_I(inode)->i_flags & F2FS_NOCOW_FL)
>  		return true;
>  
>  	/* if this is cold file, we should overwrite to avoid fragmentation */
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 596ab3e1dd7b..f6c5a3d2e659 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2374,6 +2374,7 @@ static inline void f2fs_change_bit(unsigned int nr, char *addr)
>  #define F2FS_NOATIME_FL			0x00000080 /* do not update atime */
>  #define F2FS_INDEX_FL			0x00001000 /* hash-indexed directory */
>  #define F2FS_DIRSYNC_FL			0x00010000 /* dirsync behaviour (directories only) */
> +#define F2FS_NOCOW_FL			0x00800000 /* Do not cow file */
>  #define F2FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
>  
>  /* Flags that should be inherited by new inodes from their parent. */
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 7ca545874060..ae0fec54cac6 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1692,6 +1692,7 @@ static const struct {
>  	{ F2FS_NOATIME_FL,	FS_NOATIME_FL },
>  	{ F2FS_INDEX_FL,	FS_INDEX_FL },
>  	{ F2FS_DIRSYNC_FL,	FS_DIRSYNC_FL },
> +	{ F2FS_NOCOW_FL,	FS_NOCOW_FL },
>  	{ F2FS_PROJINHERIT_FL,	FS_PROJINHERIT_FL },
>  };
>  
> @@ -1715,7 +1716,8 @@ static const struct {
>  		FS_NODUMP_FL |		\
>  		FS_NOATIME_FL |		\
>  		FS_DIRSYNC_FL |		\
> -		FS_PROJINHERIT_FL)
> +		FS_PROJINHERIT_FL |	\
> +		FS_NOCOW_FL)
>  
>  /* Convert f2fs on-disk i_flags to FS_IOC_{GET,SET}FLAGS flags */
>  static inline u32 f2fs_iflags_to_fsflags(u32 iflags)
> @@ -1753,8 +1755,6 @@ static int f2fs_ioc_getflags(struct file *filp, unsigned long arg)
>  		fsflags |= FS_ENCRYPT_FL;
>  	if (f2fs_has_inline_data(inode) || f2fs_has_inline_dentry(inode))
>  		fsflags |= FS_INLINE_DATA_FL;
> -	if (is_inode_flag_set(inode, FI_PIN_FILE))
> -		fsflags |= FS_NOCOW_FL;
>  
>  	fsflags &= F2FS_GETTABLE_FS_FL;
>  
> @@ -1794,6 +1794,22 @@ static int f2fs_ioc_setflags(struct file *filp, unsigned long arg)
>  	if (ret)
>  		goto out;
>  
> +	if ((fsflags ^ old_fsflags) & FS_NOCOW_FL) {
> +		if (!S_ISREG(inode->i_mode)) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
> +		if (f2fs_should_update_outplace(inode, NULL)) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
> +		ret = f2fs_convert_inline_inode(inode);
> +		if (ret)
> +			goto out;
> +	}
> +
>  	ret = f2fs_setflags_common(inode, iflags,
>  			f2fs_fsflags_to_iflags(F2FS_SETTABLE_FS_FL));
>  out:
> -- 
> 2.18.0.rc1