> 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 <[email protected]>
> > Reviewed-by: Sunmin Jeong <[email protected]>
> > Signed-off-by: Yeongjin Gil <[email protected]>
> > ---
> > 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);
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