linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: allocate HOT

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Message-ID: <aLOPPQFJEqoYQg24@google.com>
Date: Sat, 30 Aug 2025 23:54:37 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: allocate HOT_DATA for IPU writes

On 08/30, Chao Yu wrote:
> On 8/30/2025 4:47 AM, Jaegeuk Kim wrote:
> > On 08/29, Chao Yu wrote:
> > > On 8/28/2025 11:23 PM, Jaegeuk Kim wrote:
> > > > On 08/28, Chao Yu wrote:
> > > > > On 8/28/25 05:52, Jaegeuk Kim via Linux-f2fs-devel wrote:
> > > > > > Let's split IPU writes in hot data area to improve the GC efficiency.
> > > > > 
> > > > > I didn't get it, IPU may be not friendly for migrating data along w/ write in
> > > > > hot area?
> > > > 
> > > > This deals with IPU in the LFS mode.
> > > 
> > > Okay, so, we missed to add f2fs_lfs_mode() condition, right?
> > 
> > Why do we need that?
> 
> As you mentioned above, this deals w/ IPU in the LFS mode. Am I missing
> something?

The IPU flag indicates the data is hot. In lfs_mode, we missed to allocate
it into HOT_DATA. In normal mode, IPU will update the data in place, which
doesn't affect anything, while newly create data is also good to store in
HOT_DATA as well. So, I think we don't need other condition here.

> 
> Thanks,
> 
> > 
> > > 
> > > Thanks,
> > > 
> > > > 
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > > 
> > > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > > > > > ---
> > > > > >    fs/f2fs/segment.c | 3 ++-
> > > > > >    1 file changed, 2 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > > > > index e0f6589c6a1c..bb79dad55ac9 100644
> > > > > > --- a/fs/f2fs/segment.c
> > > > > > +++ b/fs/f2fs/segment.c
> > > > > > @@ -3688,7 +3688,8 @@ static int __get_segment_type_6(struct f2fs_io_info *fio)
> > > > > >    		if (file_is_hot(inode) ||
> > > > > >    				is_inode_flag_set(inode, FI_HOT_DATA) ||
> > > > > > -				f2fs_is_cow_file(inode))
> > > > > > +				f2fs_is_cow_file(inode) ||
> > > > > > +				is_inode_flag_set(inode, FI_NEED_IPU))
> > > > > >    			return CURSEG_HOT_DATA;
> > > > > >    		return f2fs_rw_hint_to_seg_type(F2FS_I_SB(inode),
> > > > > >    						inode->i_write_hint);