linux-kernel - RE: [PATCH RESEND] f2fs: optimize f2fs_overwrite_io() for f2fs_iomap

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Message-ID: <000101dc8b8a$cc342770$649c7650$@samsung.com>
Date: Thu, 22 Jan 2026 19:35:16 +0900
From: "Yeongjin Gil" <youngjin.gil@...sung.com>
To: "'Chao Yu'" <chao@...nel.org>, <jaegeuk@...nel.org>, <jyh429@...il.com>,
	<linux-f2fs-devel@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>
Cc: "'Sungjong Seo'" <sj1557.seo@...sung.com>, "'Sunmin Jeong'"
	<s_min.jeong@...sung.com>, "'Yeongjin Gil'" <youngjin.gil@...sung.com>
Subject: RE: [PATCH RESEND] f2fs: optimize f2fs_overwrite_io() for
 f2fs_iomap_begin

> On 1/16/2026 6:23 PM, Yeongjin Gil wrote:
> > When overwriting already allocated blocks, f2fs_iomap_begin() calls
> > f2fs_overwrite_io() to check block mappings. However,
> > f2fs_overwrite_io() iterates through all mapped blocks in the range,
> > which can be inefficient for fragmented files with large I/O requests.
> >
> > This patch optimizes f2fs_overwrite_io() by adding a 'check_first'
> > parameter and introducing __f2fs_overwrite_io() helper. When called
> > from f2fs_iomap_begin(), we only check the first mapping to determine
> > if the range is already allocated, which is sufficient for setting
> > map.m_may_create.
> >
> > This optimization significantly reduces the number of
> > f2fs_map_blocks() calls in f2fs_overwrite_io() when called from
> > f2fs_iomap_begin(), especially for fragmented files with large I/O
> requests.
> >
> > Fixes: 351bc761338d ("f2fs: optimize f2fs DIO overwrites")
> > Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>
> > Reviewed-by: Sunmin Jeong <s_min.jeong@...sung.com>
> > Signed-off-by: Yeongjin Gil <youngjin.gil@...sung.com>
> > ---
> >   fs/f2fs/data.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index
> > 2e133a723b99..bfbd717e628a 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1851,7 +1851,8 @@ int f2fs_map_blocks(struct inode *inode, struct
> f2fs_map_blocks *map, int flag)
> >   	return err;
> >   }
> >
> > -bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len)
> > +static bool __f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t
> len,
> > +				bool check_first)
> 
> Yeongjin,
> 
> You may missed to add logic related to check_first parameter?
> 
> Thanks,
I made a mistake. I will resend the v2 patch.
Thank you for the review.
> 
> >   {
> >   	struct f2fs_map_blocks map;
> >   	block_t last_lblk;
> > @@ -1877,6 +1878,11 @@ bool f2fs_overwrite_io(struct inode *inode,
> loff_t pos, size_t len)
> >   	return true;
> >   }
> >
> > +bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len) {
> > +	return __f2fs_overwrite_io(inode, pos, len, false); }
> > +
> >   static int f2fs_xattr_fiemap(struct inode *inode,
> >   				struct fiemap_extent_info *fieinfo)
> >   {
> > @@ -4443,7 +4449,7 @@ static int f2fs_iomap_begin(struct inode *inode,
> loff_t offset, loff_t length,
> >   	 * f2fs_map_lock and f2fs_balance_fs are not necessary.
> >   	 */
> >   	if ((flags & IOMAP_WRITE) &&
> > -		!f2fs_overwrite_io(inode, offset, length))
> > +		!__f2fs_overwrite_io(inode, offset, length, true))
> >   		map.m_may_create = true;
> >
> >   	err = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_DIO);